//=============================================================================================================
/**
* @file     fwd_bem_model.cpp
* @author   Christoph Dinh <chdinh@nmr.mgh.harvard.edu>;
*           Matti Hamalainen <msh@nmr.mgh.harvard.edu>
* @version  1.0
* @date     January, 2017
*
* @section  LICENSE
*
* Copyright (C) 2017, Christoph Dinh and Matti Hamalainen. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that
* the following conditions are met:
*     * Redistributions of source code must retain the above copyright notice, this list of conditions and the
*       following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
*       the following disclaimer in the documentation and/or other materials provided with the distribution.
*     * Neither the name of MNE-CPP authors nor the names of its contributors may be used
*       to endorse or promote products derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*
* @brief    Definition of the FwdBemModel Class.
*
*/

//*************************************************************************************************************
//=============================================================================================================
// INCLUDES
//=============================================================================================================

#include "fwd_bem_model.h"
#include "fwd_bem_solution.h"
#include "fwd_eeg_sphere_model.h"
#include <mne/c/mne_surface_old.h>
#include <mne/c/mne_triangle.h>
#include <mne/c/mne_source_space_old.h>

#include "fwd_comp_data.h"
#include "fwd_bem_model.h"

#include "fwd_thread_arg.h"

#include <fiff/fiff_stream.h>

#include <QFile>
#include <QList>
#include <QThread>
#include <QtConcurrent>

#define _USE_MATH_DEFINES
#include <math.h>

#include <Eigen/Dense>

static float Qx[] = {1.0,0.0,0.0};
static float Qy[] = {0.0,1.0,0.0};
static float Qz[] = {0.0,0.0,1.0};

#ifndef TRUE
#define TRUE 1
#endif

#ifndef FALSE
#define FALSE 0
#endif

#ifndef FAIL
#define FAIL -1
#endif

#ifndef OK
#define OK 0
#endif

#define X_40 0
#define Y_40 1
#define Z_40 2

#define VEC_DIFF_40(from,to,diff) {\
    (diff)[X_40] = (to)[X_40] - (from)[X_40];\
    (diff)[Y_40] = (to)[Y_40] - (from)[Y_40];\
    (diff)[Z_40] = (to)[Z_40] - (from)[Z_40];\
    }

#define VEC_COPY_40(to,from) {\
    (to)[X_40] = (from)[X_40];\
    (to)[Y_40] = (from)[Y_40];\
    (to)[Z_40] = (from)[Z_40];\
    }

#define VEC_DOT_40(x,y) ((x)[X_40]*(y)[X_40] + (x)[Y_40]*(y)[Y_40] + (x)[Z_40]*(y)[Z_40])

#define VEC_LEN_40(x) sqrt(VEC_DOT_40(x,x))

#define CROSS_PRODUCT_40(x,y,xy) {\
    (xy)[X_40] =   (x)[Y_40]*(y)[Z_40]-(y)[Y_40]*(x)[Z_40];\
    (xy)[Y_40] = -((x)[X_40]*(y)[Z_40]-(y)[X_40]*(x)[Z_40]);\
    (xy)[Z_40] =   (x)[X_40]*(y)[Y_40]-(y)[X_40]*(x)[Y_40];\
    }

#define MALLOC_40(x,t) (t *)malloc((x)*sizeof(t))

#define ALLOC_CMATRIX_40(x,y) mne_cmatrix_40((x),(y))

#define FREE_40(x) if ((char *)(x) != NULL) free((char *)(x))

#define FREE_CMATRIX_40(m) mne_free_cmatrix_40((m))

void mne_free_cmatrix_40 (float **m)
{
    if (m) {
        FREE_40(*m);
        FREE_40(m);
    }
}

static void matrix_error_40(int kind, int nr, int nc)

{
    if (kind == 1)
        printf("Failed to allocate memory pointers for a %d x %d matrix\n",nr,nc);
    else if (kind == 2)
        printf("Failed to allocate memory for a %d x %d matrix\n",nr,nc);
    else
        printf("Allocation error for a %d x %d matrix\n",nr,nc);
    if (sizeof(void *) == 4) {
        printf("This is probably because you seem to be using a computer with 32-bit architecture.\n");
        printf("Please consider moving to a 64-bit platform.");
    }
    printf("Cannot continue. Sorry.\n");
    exit(1);
}

float **mne_cmatrix_40 (int nr,int nc)

{
    int i;
    float **m;
    float *whole;

    m = MALLOC_40(nr,float *);
    if (!m) matrix_error_40(1,nr,nc);
    whole = MALLOC_40(nr*nc,float);
    if (!whole) matrix_error_40(2,nr,nc);

    for(i=0;i<nr;i++)
        m[i] = whole + i*nc;
    return m;
}

//float
Eigen::MatrixXf toFloatEigenMatrix_40(float **mat, const int m, const int n)
{
    Eigen::MatrixXf eigen_mat(m,n);

    for ( int i = 0; i < m; ++i)
        for ( int j = 0; j < n; ++j)
            eigen_mat(i,j) = mat[i][j];

    return eigen_mat;
}

void fromFloatEigenMatrix_40(const Eigen::MatrixXf& from_mat, float **& to_mat, const int m, const int n)
{
    for ( int i = 0; i < m; ++i)
        for ( int j = 0; j < n; ++j)
            to_mat[i][j] = from_mat(i,j);
}

void fromFloatEigenMatrix_40(const Eigen::MatrixXf& from_mat, float **& to_mat)
{
    fromFloatEigenMatrix_40(from_mat, to_mat, from_mat.rows(), from_mat.cols());
}

float **mne_lu_invert_40(float **mat,int dim)
/*
      * Invert a matrix using the LU decomposition from
      * LAPACK
      */
{
    Eigen::MatrixXf eigen_mat = toFloatEigenMatrix_40(mat, dim, dim);
    Eigen::MatrixXf eigen_mat_inv = eigen_mat.inverse();
    fromFloatEigenMatrix_40(eigen_mat_inv, mat);
    return mat;
}

void mne_transpose_square_40(float **mat, int n)
/*
      * In-place transpose of a square matrix
      */
{
    int j,k;
    float val;

    for (j = 1; j < n; j++)
        for (k = 0; k < j; k++) {
            val = mat[j][k];
            mat[j][k] = mat[k][j];
            mat[k][j] = val;
        }
    return;
}

float mne_dot_vectors_40(float *v1,
                       float *v2,
                       int   nn)

{
#ifdef BLAS
    int one = 1;
    float res = sdot(&nn,v1,&one,v2,&one);
    return res;
#else
    float res = 0.0;
    int   k;

    for (k = 0; k < nn; k++)
        res = res + v1[k]*v2[k];
    return res;
#endif
}

void mne_add_scaled_vector_to_40(float *v1,float scale, float *v2,int nn)

{
#ifdef BLAS
    float fscale = scale;
    int   one = 1;
    saxpy(&nn,&fscale,v1,&one,v2,&one);
#else
    int k;
    for (k = 0; k < nn; k++)
        v2[k] = v2[k] + scale*v1[k];
#endif
    return;
}

void mne_scale_vector_40(double scale,float *v,int   nn)

{
#ifdef BLAS
    float  fscale = scale;
    int    one    = 1;
    sscal(&nn,&fscale,v,&one);
#else
    int k;
    for (k = 0; k < nn; k++)
        v[k] = v[k]*scale;
#endif
}

#include <Eigen/Core>
using namespace Eigen;

float **mne_mat_mat_mult_40 (float **m1,
                             float **m2,
                             int d1,
                             int d2,
                             int d3)
/* Matrix multiplication
      * result(d1 x d3) = m1(d1 x d2) * m2(d2 x d3) */

{
#ifdef BLAS
    float **result = ALLOC_CMATRIX_40(d1,d3);
    char  *transa = "N";
    char  *transb = "N";
    float zero = 0.0;
    float one  = 1.0;
    sgemm (transa,transb,&d3,&d1,&d2,
           &one,m2[0],&d3,m1[0],&d2,&zero,result[0],&d3);
    return (result);
#else
    float **result = ALLOC_CMATRIX_40(d1,d3);
    int j,k,p;
    float sum;

    // TODO: Hack to include faster Eigen processing. This should eventually be replaced dwith pure Eigen logic.
    MatrixXf a(d1,d2);
    MatrixXf b(d2,d3);

    for (j = 0; j < d1; j++) {
        for (k = 0; k < d2; k++) {
            a(j,k) = m1[j][k];
        }
    }

    for (j = 0; j < d2; j++) {
        for (k = 0; k < d3; k++) {
            b(j,k) = m2[j][k];
        }
    }

    MatrixXf resultMat = a * b;

    for (j = 0; j < d1; j++) {
        for (k = 0; k < d3; k++) {
            result[j][k] = resultMat(j,k);
        }
    }

//    for (j = 0; j < d1; j++)
//        for (k = 0; k < d3; k++) {
//            sum = 0.0;
//            for (p = 0; p < d2; p++)
//                sum = sum + m1[j][p]*m2[p][k];
//            result[j][k] = sum;
//        }
    return (result);
#endif
}

static struct {
    int  kind;
    const QString name;
} surf_expl[] = { { FIFFV_BEM_SURF_ID_BRAIN , "inner skull" },
{ FIFFV_BEM_SURF_ID_SKULL , "outer skull" },
{ FIFFV_BEM_SURF_ID_HEAD  , "scalp" },
{ -1                      , "unknown" } };

static struct {
    int  method;
    const QString name;
} method_expl[] = { { FWD_BEM_CONSTANT_COLL , "constant collocation" },
{ FWD_BEM_LINEAR_COLL   , "linear collocation" },
{ -1                    , "unknown" } };

#define BEM_SUFFIX     "-bem.fif"
#define BEM_SOL_SUFFIX "-bem-sol.fif"

//============================= misc_util.c =============================

static QString strip_from(const QString& s, const QString& suffix)
{
    QString res;

    if (s.endsWith(suffix)) {
        res = s;
        res.chop(suffix.size());
    }
    else
        res = s;

    return res;
}

//============================= mne_coord_transforms.c =============================

typedef struct {
    int frame;
    const QString name;
} frameNameRec_40;

const QString mne_coord_frame_name_40(int frame)

{
    static frameNameRec_40 frames[] = {
        {FIFFV_COORD_UNKNOWN,"unknown"},
        {FIFFV_COORD_DEVICE,"MEG device"},
        {FIFFV_COORD_ISOTRAK,"isotrak"},
        {FIFFV_COORD_HPI,"hpi"},
        {FIFFV_COORD_HEAD,"head"},
        {FIFFV_COORD_MRI,"MRI (surface RAS)"},
        {FIFFV_MNE_COORD_MRI_VOXEL, "MRI voxel"},
        {FIFFV_COORD_MRI_SLICE,"MRI slice"},
        {FIFFV_COORD_MRI_DISPLAY,"MRI display"},
        {FIFFV_MNE_COORD_CTF_DEVICE,"CTF MEG device"},
        {FIFFV_MNE_COORD_CTF_HEAD,"CTF/4D/KIT head"},
        {FIFFV_MNE_COORD_RAS,"RAS (non-zero origin)"},
        {FIFFV_MNE_COORD_MNI_TAL,"MNI Talairach"},
        {FIFFV_MNE_COORD_FS_TAL_GTZ,"Talairach (MNI z > 0)"},
        {FIFFV_MNE_COORD_FS_TAL_LTZ,"Talairach (MNI z < 0)"},
        {-1,"unknown"}
    };
    int k;
    for (k = 0; frames[k].frame != -1; k++) {
        if (frame == frames[k].frame)
            return frames[k].name;
    }
    return frames[k].name;
}

//*************************************************************************************************************
//=============================================================================================================
// USED NAMESPACES
//=============================================================================================================

using namespace Eigen;
using namespace FIFFLIB;
using namespace MNELIB;
using namespace FWDLIB;

//*************************************************************************************************************
//=============================================================================================================
// DEFINE MEMBER METHODS
//=============================================================================================================

FwdBemModel::FwdBemModel()
:ntri       (NULL)
,np         (NULL)
,nsurf      (0)
,sigma      (NULL)
,gamma      (NULL)
,source_mult(NULL)
,field_mult (NULL)
,bem_method (FWD_BEM_UNKNOWN)
,solution   (NULL)
,nsol       (0)
,head_mri_t (NULL)
,v0         (NULL)
,use_ip_approach(false)
,ip_approach_limit(FWD_BEM_IP_APPROACH_LIMIT)
{

}

//*************************************************************************************************************

FwdBemModel::~FwdBemModel()
{
    for (int k = 0; k < this->nsurf; k++)
        delete this->surfs[k];
    FREE_40(this->ntri);
    FREE_40(this->np);
    FREE_40(this->sigma);
    FREE_40(this->source_mult);
    FREE_40(this->field_mult);
    FREE_CMATRIX_40(this->gamma);
    if(this->head_mri_t)
        delete this->head_mri_t;
    this->fwd_bem_free_solution();
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_free_solution()
{
    FREE_CMATRIX_40(this->solution); this->solution = NULL;
    this->sol_name.clear();
    FREE_40(this->v0); this->v0 = NULL;
    this->bem_method = FWD_BEM_UNKNOWN;
    this->nsol       = 0;

    return;
}

//*************************************************************************************************************

QString FwdBemModel::fwd_bem_make_bem_sol_name(const QString& name)
/*
    * Make a standard BEM solution file name
    */
{
    QString s1, s2;

    s1 = strip_from(name,".fif");
    s2 = strip_from(s1,"-sol");
    s1 = strip_from(s2,"-bem");
    s2 = QString("%1%2").arg(s1).arg(BEM_SOL_SUFFIX);
    return s2;
}

//*************************************************************************************************************

const QString& FwdBemModel::fwd_bem_explain_surface(int kind)
{
    int k;

    for (k = 0; surf_expl[k].kind >= 0; k++)
        if (surf_expl[k].kind == kind)
            return surf_expl[k].name;

    return surf_expl[k].name;
}

//*************************************************************************************************************

const QString& FwdBemModel::fwd_bem_explain_method(int method)

{
    int k;

    for (k = 0; method_expl[k].method >= 0; k++)
        if (method_expl[k].method == method)
            return method_expl[k].name;

    return method_expl[k].name;
}

//*************************************************************************************************************

int FwdBemModel::get_int(FiffStream::SPtr &stream, const FiffDirNode::SPtr &node, int what, int *res)
/*
    * Wrapper to get int's
    */
{
    FiffTag::SPtr t_pTag;
    if(node->find_tag(stream, what, t_pTag)) {
        if (t_pTag->getType() != FIFFT_INT) {
            printf("Expected an integer tag : %d (found data type %d instead)\n",what,t_pTag->getType() );
            return FAIL;
        }
        *res = *t_pTag->toInt();
        return OK;
    }
    return FAIL;
}

//*************************************************************************************************************

MneSurfaceOld *FwdBemModel::fwd_bem_find_surface(int kind)
{
    //    if (!model) {
    //        printf("No model specified for fwd_bem_find_surface");
    //        return NULL;
    //    }
    for (int k = 0; k < this->nsurf; k++)
        if (this->surfs[k]->id == kind)
            return this->surfs[k];
    printf("Desired surface (%d = %s) not found.", kind,fwd_bem_explain_surface(kind).toUtf8().constData());
    return NULL;
}

//*************************************************************************************************************

FwdBemModel *FwdBemModel::fwd_bem_load_surfaces(const QString &name, int *kinds, int nkind)
/*
* Load a set of surfaces
*/
{
    QList<MneSurfaceOld*> surfs;// = NULL;
    float      *sigma = NULL;
    float      *sigma1;
    FwdBemModel *m = NULL;
    int         j,k;

    if (nkind <= 0) {
        qCritical("No surfaces specified to fwd_bem_load_surfaces");
        return NULL;
    }

//    surfs = MALLOC_40(nkind,MneSurfaceOld*);
    sigma = MALLOC_40(nkind,float);
//    for (k = 0; k < nkind; k++)
//        surfs[k] = NULL;

    for (k = 0; k < nkind; k++) {
        surfs.append(MneSurfaceOld::read_bem_surface(name,kinds[k],TRUE,sigma+k));
        if (surfs[k] == NULL)
            goto bad;
        if ((surfs[k] = MneSurfaceOld::read_bem_surface(name,kinds[k],TRUE,sigma+k)) == NULL)
            goto bad;
        if (sigma[k] < 0.0) {
            qCritical("No conductivity available for surface %s",fwd_bem_explain_surface(kinds[k]).toUtf8().constData());
            goto bad;
        }
        if (surfs[k]->coord_frame != FIFFV_COORD_MRI) { /* We make our life much easier with this */
            qCritical("Surface %s not specified in MRI coordinates.",fwd_bem_explain_surface(kinds[k]).toUtf8().constData());
            goto bad;
        }
    }
    m = new FwdBemModel;

    m->surf_name = name;
    m->nsurf     = nkind;
    m->surfs     = surfs;
    m->sigma     = sigma;
    m->ntri      = MALLOC_40(nkind,int);
    m->np        = MALLOC_40(nkind,int);
    m->gamma = ALLOC_CMATRIX_40(nkind,nkind);
    m->source_mult = MALLOC_40(nkind,float);
    m->field_mult  = MALLOC_40(nkind,float);
    /*
       * Dirty trick for the zero conductivity outside
       */
    sigma1 = MALLOC_40(nkind+1,float);
    sigma1[0] = 0.0;
    sigma  = sigma1+1;
    for (k = 0; k < m->nsurf; k++)
        sigma[k] = m->sigma[k];
    /*
       * Gamma factors and multipliers
       */
    for (j = 0; j < m->nsurf; j++) {
        m->ntri[j] = m->surfs[j]->ntri;
        m->np[j]   = m->surfs[j]->np;
        m->source_mult[j] = 2.0/(sigma[j]+sigma[j-1]);
        m->field_mult[j] = sigma[j]-sigma[j-1];
        for (k = 0; k < m->nsurf; k++)
            m->gamma[j][k] = (sigma[k]-sigma[k-1])/(sigma[j]+sigma[j-1]);
    }
    FREE_40(sigma1);

    return m;

bad : {
        FREE_40(sigma);
        for (k = 0; k < surfs.size(); k++)
            delete surfs[k];
//        FREE_40(surfs);
        surfs.clear();
        return NULL;
    }
}

//*************************************************************************************************************

FwdBemModel *FwdBemModel::fwd_bem_load_homog_surface(const QString &name)
/*
* Load surfaces for the homogeneous model
*/
{
    int kinds[] = { FIFFV_BEM_SURF_ID_BRAIN };
    int nkind   = 1;

    return fwd_bem_load_surfaces(name,kinds,nkind);
}

//*************************************************************************************************************

FwdBemModel *FwdBemModel::fwd_bem_load_three_layer_surfaces(const QString &name)
/*
* Load surfaces for three-layer model
*/
{
    int kinds[] = { FIFFV_BEM_SURF_ID_HEAD, FIFFV_BEM_SURF_ID_SKULL, FIFFV_BEM_SURF_ID_BRAIN };
    int nkind   = 3;

    return fwd_bem_load_surfaces(name,kinds,nkind);
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_load_solution(const QString &name, int bem_method, FwdBemModel *m)
/*
    * Load the potential solution matrix and attach it to the model:
    *
    * return values:
    *
    *       TRUE   found a suitable solution
    *       FALSE  did not find a suitable solution
    *       FAIL   error in reading the solution
    *
    */
{
    QFile file(name);
    FiffStream::SPtr stream(new FiffStream(&file));

    float       **sol = NULL;
    FiffDirNode::SPtr bem_node;
    int         method;
    FiffTag::SPtr t_pTag;
    int         nsol;

    if(!stream->open())
        goto not_found;

    /*
       * Find the BEM data
       */
    {
        QList<FiffDirNode::SPtr> nodes = stream->dirtree()->dir_tree_find(FIFFB_BEM);

        if (nodes.size() == 0) {
            printf ("No BEM data in %s",name.toUtf8().constData());
            goto not_found;
        }
        bem_node = nodes[0];
    }
    /*
        * Approximation method
        */
    if (get_int(stream,bem_node,FIFF_BEM_APPROX,&method) != OK)
        goto not_found;
    if (method == FIFFV_BEM_APPROX_CONST)
        method = FWD_BEM_CONSTANT_COLL;
    else if (method == FIFFV_BEM_APPROX_LINEAR)
        method = FWD_BEM_LINEAR_COLL;
    else {
        printf ("Cannot handle BEM approximation method : %d",method);
        goto bad;
    }
    if (bem_method != FWD_BEM_UNKNOWN && method != bem_method) {
        printf("Approximation method in file : %d desired : %d",method,bem_method);
        goto not_found;
    }
    {
        int         dim,k;

        if (!bem_node->find_tag(stream, FIFF_BEM_POT_SOLUTION, t_pTag))
            goto bad;
        qint32 ndim;
        QVector<qint32> dims;
        t_pTag->getMatrixDimensions(ndim, dims);

        if (ndim != 2) {
            printf("Expected a two-dimensional solution matrix instead of a %d dimensional one",ndim);
            goto bad;
        }
        for (k = 0, dim = 0; k < m->nsurf; k++)
            dim = dim + ((method == FWD_BEM_LINEAR_COLL) ? m->surfs[k]->np : m->surfs[k]->ntri);
        if (dims[0] != dim || dims[1] != dim) {
            printf("Expected a %d x %d solution matrix instead of a %d x %d  one",dim,dim,dims[0],dims[1]);
            goto not_found;
        }

        MatrixXf tmp_sol = t_pTag->toFloatMatrix().transpose();
        sol = ALLOC_CMATRIX_40(tmp_sol.rows(),tmp_sol.cols());
        fromFloatEigenMatrix_40(tmp_sol, sol);
        nsol = dims[1];
    }
    if(m)
        m->fwd_bem_free_solution();
    m->sol_name = name;
    m->solution = sol;
    m->nsol     = nsol;
    m->bem_method = method;
    stream->close();

    return TRUE;

bad : {
        stream->close();
        FREE_CMATRIX_40(sol);
        return FAIL;
    }

not_found : {
        stream->close();
        FREE_CMATRIX_40(sol);
        return FALSE;
    }
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_set_head_mri_t(FwdBemModel *m, FiffCoordTransOld *t)
/*
    * Set the coordinate transformation
    */
{
    if (t->from == FIFFV_COORD_HEAD && t->to == FIFFV_COORD_MRI) {
        if(m->head_mri_t)
            delete m->head_mri_t;
        m->head_mri_t = new FiffCoordTransOld( *t );
        return OK;
    }
    else if (t->from == FIFFV_COORD_MRI && t->to == FIFFV_COORD_HEAD) {
        if(m->head_mri_t)
            delete m->head_mri_t;
        m->head_mri_t = t->fiff_invert_transform();
        return OK;
    }
    else {
        printf ("Improper coordinate transform delivered to fwd_bem_set_head_mri_t");
        return FAIL;
    }
}

//*************************************************************************************************************

MneSurfaceOld* FwdBemModel::make_guesses(MneSurfaceOld* guess_surf, float guessrad, float *guess_r0, float grid, float exclude, float mindist)		   /* Exclude points closer than this to
                                                        * the guess boundary surface */
/*
     * Make a guess space inside a sphere
     */
{
    char *bemname     = NULL;
    MneSurfaceOld* sphere = NULL;
    MneSurfaceOld* res    = NULL;
    int        k;
    float      dist;
    float      r0[] = { 0.0, 0.0, 0.0 };

    if (!guess_r0)
        guess_r0 = r0;

    if (!guess_surf) {
        printf("Making a spherical guess space with radius %7.1f mm...\n",1000*guessrad);
        //#ifdef USE_SHARE_PATH
        //    if ((bemname = mne_compose_mne_name("share/mne","icos.fif")) == NULL)
        //#else
        //    if ((bemname = mne_compose_mne_name("setup/mne","icos.fif")) == NULL)
        //#endif
        //      goto out;

        //    QFile bemFile("/usr/pubsw/packages/mne/stable/share/mne/icos.fif");

        QFile bemFile(QString(QCoreApplication::applicationDirPath() + "/resources/general/surf2bem/icos.fif"));
        if ( !QCoreApplication::startingUp() )
            bemFile.setFileName(QCoreApplication::applicationDirPath() + QString("/resources/general/surf2bem/icos.fif"));
        else if (!bemFile.exists())
            bemFile.setFileName("./resources/general/surf2bem/icos.fif");

        if( !bemFile.exists () ){
            qDebug() << bemFile.fileName() << "does not exists.";
            goto out;
        }

        bemname = MALLOC_40(strlen(bemFile.fileName().toUtf8().data())+1,char);
        strcpy(bemname,bemFile.fileName().toUtf8().data());

        if ((sphere = MneSourceSpaceOld::read_bem_surface(bemname,9003,FALSE,NULL)) == NULL)
            goto out;

        for (k = 0; k < sphere->np; k++) {
            dist = VEC_LEN_40(sphere->rr[k]);
            sphere->rr[k][X_40] = guessrad*sphere->rr[k][X_40]/dist + guess_r0[X_40];
            sphere->rr[k][Y_40] = guessrad*sphere->rr[k][Y_40]/dist + guess_r0[Y_40];
            sphere->rr[k][Z_40] = guessrad*sphere->rr[k][Z_40]/dist + guess_r0[Z_40];
        }
        if (MneSurfaceOrVolume::mne_source_space_add_geometry_info((MneSourceSpaceOld*)sphere,TRUE) == FAIL)
            goto out;
        guess_surf = sphere;
    }
    else {
        printf("Guess surface (%d = %s) is in %s coordinates\n",
               guess_surf->id,FwdBemModel::fwd_bem_explain_surface(guess_surf->id).toUtf8().constData(),
               mne_coord_frame_name_40(guess_surf->coord_frame).toUtf8().constData());
    }
    printf("Filtering (grid = %6.f mm)...\n",1000*grid);
    res = (MneSurfaceOld*)MneSurfaceOrVolume::make_volume_source_space(guess_surf,grid,exclude,mindist);

out : {
        FREE_40(bemname);
        if(sphere)
            delete sphere;
        return res;
    }
}

//*************************************************************************************************************

double FwdBemModel::calc_beta(double *rk, double *rk1)

{
    double rkk1[3];
    double size;
    double res;

    VEC_DIFF_40(rk,rk1,rkk1);
    size = VEC_LEN_40(rkk1);

    res = log((VEC_LEN_40(rk)*size + VEC_DOT_40(rk,rkk1))/
              (VEC_LEN_40(rk1)*size + VEC_DOT_40(rk1,rkk1)))/size;
    return (res);
}

//*************************************************************************************************************

void FwdBemModel::lin_pot_coeff(float *from, MneTriangle* to, double omega[])	/* The final result */
/*
          * The linear potential matrix element computations
          */
{
    double y1[3],y2[3],y3[3];	/* Corners with origin at from */
    double *y[5];
    double **yy;
    double l1,l2,l3;		/* Lengths of y1, y2, and y3 */
    double solid;			/* The standard solid angle */
    double vec_omega[3];		/* The cross-product integral */
    double cross[3];		/* y1 x y2 */
    double triple;		/* VEC_DOT_40(y1 x y2,y3) */
    double ss;
    double beta[3],bbeta[3];
    int   j,k;
    double z[3];
    double n2,area2;
    double diff[3];
    static const double solid_eps = 4.0*M_PI/1.0E6;
    /*
       * This circularity makes things easy for us...
       */
    y[0] = y3;
    y[1] = y1;
    y[2] = y2;
    y[3] = y3;
    y[4] = y1;
    yy = y + 1;			/* yy can have index -1! */
    /*
       * The standard solid angle computation
       */
    VEC_DIFF_40(from,to->r1,y1);
    VEC_DIFF_40(from,to->r2,y2);
    VEC_DIFF_40(from,to->r3,y3);

    CROSS_PRODUCT_40(y1,y2,cross);
    triple = VEC_DOT_40(cross,y3);

    l1 = VEC_LEN_40(y1);
    l2 = VEC_LEN_40(y2);
    l3 = VEC_LEN_40(y3);
    ss = (l1*l2*l3+VEC_DOT_40(y1,y2)*l3+VEC_DOT_40(y1,y3)*l2+VEC_DOT_40(y2,y3)*l1);
    solid  = 2.0*atan2(triple,ss);
    if (std::fabs(solid) < solid_eps) {
        for (k = 0; k < 3; k++)
            omega[k] = 0.0;
    }
    else {
        /*
         * Calculate the magic vector vec_omega
         */
        for (j = 0; j < 3; j++)
            beta[j] = calc_beta(yy[j],yy[j+1]);
        bbeta[0] = beta[2] - beta[0];
        bbeta[1] = beta[0] - beta[1];
        bbeta[2] = beta[1] - beta[2];

        for (j = 0; j < 3; j++)
            vec_omega[j] = 0.0;
        for (j = 0; j < 3; j++)
            for (k = 0; k < 3; k++)
                vec_omega[k] = vec_omega[k] + bbeta[j]*yy[j][k];
        /*
         * Put it all together...
         */
        area2 = 2.0*to->area;
        n2 = 1.0/(area2*area2);
        for (k = 0; k < 3; k++) {
            CROSS_PRODUCT_40(yy[k+1],yy[k-1],z);
            VEC_DIFF_40(yy[k+1],yy[k-1],diff);
            omega[k] = n2*(-area2*VEC_DOT_40(z,to->nn)*solid +
                           triple*VEC_DOT_40(diff,vec_omega));
        }
    }
#ifdef CHECK
    /*
       * Check it out!
       *
       * omega1 + omega2 + omega3 = solid
       */
    rel1 = (solid + omega[X_40]+omega[Y_40]+omega[Z_40])/solid;
    /*
       * The other way of evaluating...
       */
    for (j = 0; j < 3; j++)
        check[j] = 0;
    for (k = 0; k < 3; k++) {
        CROSS_PRODUCT_40(to->nn[to],yy[k],z);
        for (j = 0; j < 3; j++)
            check[j] = check[j] + omega[k]*z[j];
    }
    for (j = 0; j < 3; j++)
        check[j] = -area2*check[j]/triple;
    fprintf (stderr,"(%g,%g,%g) =? (%g,%g,%g)\n",
             check[X_40],check[Y_40],check[Z_40],
             vec_omega[X_40],vec_omega[Y_40],vec_omega[Z_40]);
    for (j = 0; j < 3; j++)
        check[j] = check[j] - vec_omega[j];
    rel2 = sqrt(VEC_DOT_40(check,check)/VEC_DOT_40(vec_omega,vec_omega));
    fprintf (stderr,"err1 = %g, err2 = %g\n",100*rel1,100*rel2);
#endif
    return;
}

//*************************************************************************************************************

void FwdBemModel::correct_auto_elements(MneSurfaceOld *surf, float **mat)
/*
          * Improve auto-element approximation...
          */
{
    float *row;
    float sum,miss;
    int   nnode = surf->np;
    int   ntri  = surf->ntri;
    int   nmemb;
    int   j,k;
    float pi2 = 2.0*M_PI;
    MneTriangle*   tri;

#ifdef SIMPLE
    for (j = 0; j < nnode; j++) {
        row = mat[j];
        sum = 0.0;
        for (k = 0; k < nnode; k++)
            sum = sum + row[k];
        fprintf (stderr,"row %d sum = %g missing = %g\n",j+1,sum/pi2,
                 1.0-sum/pi2);
        row[j] = pi2 - sum;
    }
#else
    for (j = 0; j < nnode; j++) {
        /*
         * How much is missing?
         */
        row = mat[j];
        sum = 0.0;
        for (k = 0; k < nnode; k++)
            sum = sum + row[k];
        miss  = pi2-sum;
        nmemb = surf->nneighbor_tri[j];
        /*
         * The node itself receives one half
         */
        row[j] = miss/2.0;
        /*
         * The rest is divided evenly among the member nodes...
         */
        miss = miss/(4.0*nmemb);
        for (k = 0,tri = surf->tris; k < ntri; k++,tri++) {
            if (tri->vert[0] == j) {
                row[tri->vert[1]] = row[tri->vert[1]] + miss;
                row[tri->vert[2]] = row[tri->vert[2]] + miss;
            }
            else if (tri->vert[1] == j) {
                row[tri->vert[0]] = row[tri->vert[0]] + miss;
                row[tri->vert[2]] = row[tri->vert[2]] + miss;
            }
            else if (tri->vert[2] == j) {
                row[tri->vert[0]] = row[tri->vert[0]] + miss;
                row[tri->vert[1]] = row[tri->vert[1]] + miss;
            }
        }
        /*
         * Just check it it out...
         *
        for (k = 0, sum = 0; k < nnode; k++)
          sum = sum + row[k];
        fprintf (stderr,"row %d sum = %g\n",j+1,sum/pi2);
        */
    }
#endif
    return;
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_lin_pot_coeff(const QList<MneSurfaceOld*>& surfs)
/*
* Calculate the coefficients for linear collocation approach
*/
{
    float **mat = NULL;
    float **sub_mat = NULL;
    int   np1,np2,ntri,np_tot,np_max;
    float **nodes;
    MneTriangle*   tri;
    double omega[3];
    double *row = NULL;
    int    j,k,p,q,c;
    int    joff,koff;
    MneSurfaceOld* surf1;
    MneSurfaceOld* surf2;

    for (p = 0, np_tot = np_max = 0; p < surfs.size(); p++) {
        np_tot += surfs[p]->np;
        if (surfs[p]->np > np_max)
            np_max = surfs[p]->np;
    }

    mat = ALLOC_CMATRIX_40(np_tot,np_tot);
    for (j = 0; j < np_tot; j++)
        for (k = 0; k < np_tot; k++)
            mat[j][k] = 0.0;
    row        = MALLOC_40(np_max,double);
    sub_mat = MALLOC_40(np_max,float *);
    for (p = 0, joff = 0; p < surfs.size(); p++, joff = joff + np1) {
        surf1 = surfs[p];
        np1   = surf1->np;
        nodes = surf1->rr;
        for (q = 0, koff = 0; q < surfs.size(); q++, koff = koff + np2) {
            surf2 = surfs[q];
            np2   = surf2->np;
            ntri  = surf2->ntri;

            fprintf(stderr,"\t\t%s (%d) -> %s (%d) ... ",
                    fwd_bem_explain_surface(surf1->id).toUtf8().constData(),np1,
                    fwd_bem_explain_surface(surf2->id).toUtf8().constData(),np2);

            for (j = 0; j < np1; j++) {
                for (k = 0; k < np2; k++)
                    row[k] = 0.0;
                for (k = 0, tri = surf2->tris; k < ntri; k++,tri++) {
                    /*
               * No contribution from a triangle that
               * this vertex belongs to
               */
                    if (p == q && (tri->vert[0] == j || tri->vert[1] == j || tri->vert[2] == j))
                        continue;
                    /*
               * Otherwise do the hard job
               */
                    lin_pot_coeff (nodes[j],tri,omega);
                    for (c = 0; c < 3; c++)
                        row[tri->vert[c]] = row[tri->vert[c]] - omega[c];
                }
                for (k = 0; k < np2; k++)
                    mat[j+joff][k+koff] = row[k];
            }
            if (p == q) {
                for (j = 0; j < np1; j++)
                    sub_mat[j] = mat[j+joff]+koff;
                correct_auto_elements (surf1,sub_mat);
            }
            fprintf(stderr,"[done]\n");
        }
    }
    FREE_40(row);
    FREE_40(sub_mat);
    return(mat);
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_linear_collocation_solution(FwdBemModel *m)
/*
     * Compute the linear collocation potential solution
     */
{
    float **coeff = NULL;
    float ip_mult;
    int k;

    if(m)
        m->fwd_bem_free_solution();

    fprintf(stderr,"\nComputing the linear collocation solution...\n");
    fprintf (stderr,"\tMatrix coefficients...\n");
    if ((coeff = fwd_bem_lin_pot_coeff (m->surfs)) == NULL)
        goto bad;

    for (k = 0, m->nsol = 0; k < m->nsurf; k++)
        m->nsol += m->surfs[k]->np;

    fprintf (stderr,"\tInverting the coefficient matrix...\n");
    if ((m->solution = fwd_bem_multi_solution (coeff,m->gamma,m->nsurf,m->np)) == NULL)
        goto bad;

    /*
       * IP approach?
       */
    if ((m->nsurf == 3) &&
            (ip_mult = m->sigma[m->nsurf-2]/m->sigma[m->nsurf-1]) <= m->ip_approach_limit) {
        float **ip_solution = NULL;

        fprintf (stderr,"IP approach required...\n");

        fprintf (stderr,"\tMatrix coefficients (homog)...\n");
        QList<MneSurfaceOld*> last_surfs;
        last_surfs << m->surfs.last();
        if ((coeff = fwd_bem_lin_pot_coeff(last_surfs))== NULL)//m->surfs+m->nsurf-1,1)) == NULL)
            goto bad;

        fprintf (stderr,"\tInverting the coefficient matrix (homog)...\n");
        if ((ip_solution = fwd_bem_homog_solution (coeff,m->surfs[m->nsurf-1]->np)) == NULL)
            goto bad;

        fprintf (stderr,"\tModify the original solution to incorporate IP approach...\n");

        fwd_bem_ip_modify_solution(m->solution,ip_solution,ip_mult,m->nsurf,m->np);
        FREE_CMATRIX_40(ip_solution);

    }
    m->bem_method = FWD_BEM_LINEAR_COLL;
    fprintf(stderr,"Solution ready.\n");
    return OK;

bad : {
        if(m)
            m->fwd_bem_free_solution();
        FREE_CMATRIX_40(coeff);
        return FAIL;
    }
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_multi_solution(float **solids, float **gamma, int nsurf, int *ntri)       /* Number of triangles or nodes on each surface */
/*
          * Invert I - solids/(2*M_PI)
          * Take deflation into account
          * The matrix is destroyed after inversion
          * This is the general multilayer case
          */
{
    int j,k,p,q;
    float defl;
    float pi2 = 1.0/(2*M_PI);
    float mult;
    int   joff,koff,jup,kup,ntot;

    for (j = 0,ntot = 0; j < nsurf; j++)
        ntot += ntri[j];
    defl = 1.0/ntot;
    /*
       * Modify the matrix
       */
    for (p = 0, joff = 0; p < nsurf; p++) {
        jup = ntri[p] + joff;
        for (q = 0, koff = 0; q < nsurf; q++) {
            kup = ntri[q] + koff;
            mult = (gamma == NULL) ? pi2 : pi2*gamma[p][q];
            for (j = joff; j < jup; j++)
                for (k = koff; k < kup; k++)
                    solids[j][k] = defl - solids[j][k]*mult;
            koff = kup;
        }
        joff = jup;
    }
    for (k = 0; k < ntot; k++)
        solids[k][k] = solids[k][k] + 1.0;

    return (mne_lu_invert_40(solids,ntot));
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_homog_solution(float **solids, int ntri)
/*
          * Invert I - solids/(2*M_PI)
          * Take deflation into account
          * The matrix is destroyed after inversion
          * This is the homogeneous model case
          */
{
    return fwd_bem_multi_solution (solids,NULL,1,&ntri);
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_ip_modify_solution(float **solution, float **ip_solution, float ip_mult, int nsurf, int *ntri)                  /* Number of triangles (nodes) on each surface */
/*
          * Modify the solution according to the IP approach
          */
{
    int s;
    int j,k,joff,koff,ntot,nlast;
    float mult;
    float *row = NULL;
    float **sub = NULL;

    for (s = 0, koff = 0; s < nsurf-1; s++)
        koff = koff + ntri[s];
    nlast = ntri[nsurf-1];
    ntot  = koff + nlast;

    row = MALLOC_40(nlast,float);
    sub = MALLOC_40(ntot,float *);
    mult = (1.0 + ip_mult)/ip_mult;

    fprintf(stderr,"\t\tCombining...");
#ifndef OLD
    fprintf(stderr,"t ");
    mne_transpose_square_40(ip_solution,nlast);
#endif
    for (s = 0, joff = 0; s < nsurf; s++) {
        fprintf(stderr,"%d3 ",s+1);
        /*
        * Pick the correct submatrix
        */
        for (j = 0; j < ntri[s]; j++)
            sub[j] = solution[j+joff]+koff;
        /*
        * Multiply
        */
#ifdef OLD
        for (j = 0; j < ntri[s]; j++) {
            for (k = 0; k < nlast; k++) {
                res = mne_dot_vectors_skip_skip(sub[j],1,ip_solution[0]+k,nlast,nlast);
                row[k] = sub[j][k] - 2.0*res;
            }
            for (k = 0; k < nlast; k++)
                sub[j][k] = row[k];
        }
#else
        for (j = 0; j < ntri[s]; j++) {
            for (k = 0; k < nlast; k++)
                row[k] = mne_dot_vectors_40(sub[j],ip_solution[k],nlast);
            mne_add_scaled_vector_to_40(row,-2.0,sub[j],nlast);
        }
#endif
        joff = joff+ntri[s];
    }
#ifndef OLD
    fprintf(stderr,"t ");
    mne_transpose_square_40(ip_solution,nlast);
#endif
    fprintf(stderr,"33 ");
    /*
    * The lower right corner is a special case
    */
    for (j = 0; j < nlast; j++)
        for (k = 0; k < nlast; k++)
            sub[j][k] = sub[j][k] + mult*ip_solution[j][k];
    /*
    * Final scaling
    */
    fprintf(stderr,"done.\n\t\tScaling...");
    mne_scale_vector_40(ip_mult,solution[0],ntot*ntot);
    fprintf(stderr,"done.\n");
    FREE_40(row); FREE_40(sub);
    return;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_check_solids(float **angles, int ntri1, int ntri2, float desired)
/*
* Check the angle computations
*/
{
    float *sums = MALLOC_40(ntri1,float);
    float sum;
    int j,k;
    int res = 0;

    for (j = 0; j < ntri1; j++) {
        sum = 0;
        for (k = 0; k < ntri2; k++)
            sum = sum + angles[j][k];
        sums[j] = sum/(2*M_PI);
    }
    for (j = 0; j < ntri1; j++)
        /*
        * Three cases:
        * same surface: sum = 2*pi
        * to outer:     sum = 4*pi
        * to inner:     sum = 0*pi;
        */
        if (std::fabs(sums[j]-desired) > 1e-4) {
            printf("solid angle matrix: rowsum[%d] = 2PI*%g",
                   j+1,sums[j]);
            res = -1;
            break;
        }
    FREE_40(sums);
    return res;
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_solid_angles(const QList<MneSurfaceOld*>& surfs)
/*
          * Compute the solid angle matrix
          */
{
    MneSurfaceOld* surf1;
    MneSurfaceOld* surf2;
    MneTriangle* tri;
    int ntri1,ntri2,ntri_tot;
    int j,k,p,q;
    int joff,koff;
    float **solids;
    float result;
    float **sub_solids = NULL;
    float desired;

    for (p = 0,ntri_tot = 0; p < surfs.size(); p++)
        ntri_tot += surfs[p]->ntri;

    sub_solids = MALLOC_40(ntri_tot,float *);
    solids = ALLOC_CMATRIX_40(ntri_tot,ntri_tot);
    for (p = 0, joff = 0; p < surfs.size(); p++, joff = joff + ntri1) {
        surf1 = surfs[p];
        ntri1 = surf1->ntri;
        for (q = 0, koff = 0; q < surfs.size(); q++, koff = koff + ntri2) {
            surf2 = surfs[q];
            ntri2 = surf2->ntri;
            fprintf(stderr,"\t\t%s (%d) -> %s (%d) ... ",fwd_bem_explain_surface(surf1->id).toUtf8().constData(),ntri1,fwd_bem_explain_surface(surf2->id).toUtf8().constData(),ntri2);
            for (j = 0; j < ntri1; j++)
                for (k = 0, tri = surf2->tris; k < ntri2; k++, tri++) {
                    if (p == q && j == k)
                        result = 0.0;
                    else
                        result = MneSurfaceOrVolume::solid_angle (surf1->tris[j].cent,tri);
                    solids[j+joff][k+koff] = result;
                }
            for (j = 0; j < ntri1; j++)
                sub_solids[j] = solids[j+joff]+koff;
            fprintf(stderr,"[done]\n");
            if (p == q)
                desired = 1;
            else if (p < q)
                desired = 0;
            else
                desired = 2;
            if (fwd_bem_check_solids(sub_solids,ntri1,ntri2,desired) == FAIL) {
                FREE_CMATRIX_40(solids);
                FREE_40(sub_solids);
                return NULL;
            }
        }
    }
    FREE_40(sub_solids);
    return (solids);
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_constant_collocation_solution(FwdBemModel *m)
/*
     * Compute the solution for the constant collocation approach
     */
{
    float  **solids = NULL;
    int    k;
    float  ip_mult;

    if(m)
        m->fwd_bem_free_solution();

    fprintf(stderr,"\nComputing the constant collocation solution...\n");
    fprintf(stderr,"\tSolid angles...\n");
    if ((solids = fwd_bem_solid_angles(m->surfs)) == NULL)
        goto bad;

    for (k = 0, m->nsol = 0; k < m->nsurf; k++)
        m->nsol += m->surfs[k]->ntri;

    fprintf (stderr,"\tInverting the coefficient matrix...\n");
    if ((m->solution = fwd_bem_multi_solution (solids,m->gamma,m->nsurf,m->ntri)) == NULL)
        goto bad;
    /*
       * IP approach?
       */
    if ((m->nsurf == 3) &&
            (ip_mult = m->sigma[m->nsurf-2]/m->sigma[m->nsurf-1]) <= m->ip_approach_limit) {
        float **ip_solution = NULL;

        fprintf (stderr,"IP approach required...\n");

        fprintf (stderr,"\tSolid angles (homog)...\n");
        QList<MneSurfaceOld*> last_surfs;
        last_surfs << m->surfs.last();
        if ((solids = fwd_bem_solid_angles (last_surfs)) == NULL)//m->surfs+m->nsurf-1,1)) == NULL)
            goto bad;

        fprintf (stderr,"\tInverting the coefficient matrix (homog)...\n");
        if ((ip_solution = fwd_bem_homog_solution (solids,m->surfs[m->nsurf-1]->ntri)) == NULL)
            goto bad;

        fprintf (stderr,"\tModify the original solution to incorporate IP approach...\n");
        fwd_bem_ip_modify_solution(m->solution,ip_solution,ip_mult,m->nsurf,m->ntri);
        FREE_CMATRIX_40(ip_solution);
    }
    m->bem_method = FWD_BEM_CONSTANT_COLL;
    fprintf (stderr,"Solution ready.\n");

    return OK;

bad : {
        if(m)
            m->fwd_bem_free_solution();
        FREE_CMATRIX_40(solids);
        return FAIL;
    }
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_compute_solution(FwdBemModel *m, int bem_method)
/*
* Compute the solution
*/
{
    /*
        * Compute the solution
        */
    if (bem_method == FWD_BEM_LINEAR_COLL)
        return fwd_bem_linear_collocation_solution(m);
    else if (bem_method == FWD_BEM_CONSTANT_COLL)
        return fwd_bem_constant_collocation_solution(m);

    if(m)
        m->fwd_bem_free_solution();
    printf ("Unknown BEM method: %d\n",bem_method);
    return FAIL;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_load_recompute_solution(const QString& name, int bem_method, int force_recompute, FwdBemModel *m)
/*
* Load or recompute the potential solution matrix
*/
{
    int solres;

    if (!m) {
        printf ("No model specified for fwd_bem_load_recompute_solution");
        return FAIL;
    }

    if (!force_recompute) {
        if(m)
            m->fwd_bem_free_solution();
        solres = fwd_bem_load_solution(name,bem_method,m);
        if (solres == TRUE) {
            fprintf(stderr,"\nLoaded %s BEM solution from %s\n",fwd_bem_explain_method(m->bem_method).toUtf8().constData(),name.toUtf8().constData());
            return OK;
        }
        else if (solres == FAIL)
            return FAIL;
#ifdef DEBUG
        else
            fprintf(stderr,"Desired BEM  solution not available in %s (%s)\n",name,err_get_error());
#endif
    }
    if (bem_method == FWD_BEM_UNKNOWN)
        bem_method = FWD_BEM_LINEAR_COLL;
    return fwd_bem_compute_solution(m,bem_method);
}

//*************************************************************************************************************

float FwdBemModel::fwd_bem_inf_field(float *rd, float *Q, float *rp, float *dir)     /* Which field component */
/*
     * Infinite-medium magnetic field
     * (without \mu_0/4\pi)
     */
{
    float diff[3],diff2,cross[3];

    VEC_DIFF_40(rd,rp,diff);
    diff2 = VEC_DOT_40(diff,diff);
    CROSS_PRODUCT_40(Q,diff,cross);

    return (VEC_DOT_40(cross,dir)/(diff2*sqrt(diff2)));
}

//*************************************************************************************************************

float FwdBemModel::fwd_bem_inf_pot(float *rd, float *Q, float *rp)	/* Potential point */
/*
     * The infinite medium potential
     */
{
    float diff[3];
    float diff2;
    VEC_DIFF_40(rd,rp,diff);
    diff2 = VEC_DOT_40(diff,diff);
    return (VEC_DOT_40(Q,diff)/(4.0*M_PI*diff2*sqrt(diff2)));
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_specify_els(FwdBemModel* m, FwdCoilSet *els)
/*
     * Set up for computing the solution at a set of electrodes
     */
{
    FwdCoil*     el;
    MneSurfaceOld*  scalp;
    int         k,p,q,v;
    float       *one_sol,*pick_sol;
    float       r[3],w[3],dist;
    int         best;
    MneTriangle* tri;
    float       x,y,z;
    FwdBemSolution* sol;

    if (!m) {
        printf("Model missing in fwd_bem_specify_els");
        goto bad;
    }
    if (!m->solution) {
        printf("Solution not computed in fwd_bem_specify_els");
        goto bad;
    }
    if (!els || els->ncoil == 0)
        return OK;
    els->fwd_free_coil_set_user_data();
    /*
       * Hard work follows
       */
    els->user_data = sol = new FwdBemSolution();
    els->user_data_free = FwdBemSolution::fwd_bem_free_coil_solution;

    sol->ncoil = els->ncoil;
    sol->np    = m->nsol;
    sol->solution  = ALLOC_CMATRIX_40(sol->ncoil,sol->np);
    /*
       * Go through all coils
       */
    for (k = 0; k < els->ncoil; k++) {
        el = els->coils[k];
        one_sol = sol->solution[k];
        for (q = 0; q < m->nsol; q++)
            one_sol[q] = 0.0;
        scalp = m->surfs[0];
        /*
         * Go through all 'integration points'
         */
        for (p = 0; p < el->np; p++) {
            VEC_COPY_40(r,el->rmag[p]);
            if (m->head_mri_t != NULL)
                FiffCoordTransOld::fiff_coord_trans(r,m->head_mri_t,FIFFV_MOVE);
            best = MneSurfaceOrVolume::mne_project_to_surface(scalp,NULL,r,FALSE,&dist);
            if (best < 0) {
                printf("One of the electrodes could not be projected onto the scalp surface. How come?");
                goto bad;
            }
            if (m->bem_method == FWD_BEM_CONSTANT_COLL) {
                /*
             * Simply pick the value at the triangle
             */
                pick_sol = m->solution[best];
                for (q = 0; q < m->nsol; q++)
                    one_sol[q] += el->w[p]*pick_sol[q];
            }
            else if (m->bem_method == FWD_BEM_LINEAR_COLL) {
                /*
             * Calculate a linear interpolation between the vertex values
             */
                tri = scalp->tris+best;
                MneSurfaceOrVolume::mne_triangle_coords(r,scalp,best,&x,&y,&z);

                w[X_40] = el->w[p]*(1.0 - x - y);
                w[Y_40] = el->w[p]*x;
                w[Z_40] = el->w[p]*y;
                for (v = 0; v < 3; v++) {
                    pick_sol = m->solution[tri->vert[v]];
                    for (q = 0; q < m->nsol; q++)
                        one_sol[q] += w[v]*pick_sol[q];
                }
            }
            else {
                printf("Unknown BEM approximation method : %d\n",m->bem_method);
                goto bad;
            }
        }
    }
    return OK;

bad : {
        els->fwd_free_coil_set_user_data();
        return FAIL;
    }
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_pot_grad_calc(float *rd, float *Q, FwdBemModel* m, FwdCoilSet* els, int all_surfs, float *xgrad, float *ygrad, float *zgrad)
/*
* Compute the potentials due to a current dipole
*/
{
    MneTriangle* tri;
    int         ntri;
    int         s,k,p,nsol,pp;
    float       mult;
    float       *v0,ee[3];
    float       **solution;
    float       mri_rd[3],mri_Q[3];

    float  *grads[3];
    float  *grad;

    grads[0] = xgrad;
    grads[1] = ygrad;
    grads[2] = zgrad;

    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;

    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (pp = 0; pp < 3; pp++) {
        grad = grads[pp];

        for (p = 0; p < 3; p++)
            ee[p] = p == pp ? 1.0 : 0.0;
        if (m->head_mri_t)
            FiffCoordTransOld::fiff_coord_trans(ee,m->head_mri_t,FIFFV_NO_MOVE);

        for (s = 0, p = 0; s < m->nsurf; s++) {
            ntri = m->surfs[s]->ntri;
            tri  = m->surfs[s]->tris;
            mult = m->source_mult[s];
            for (k = 0; k < ntri; k++, tri++)
                v0[p++] = mult*fwd_bem_inf_pot_der(mri_rd,mri_Q,tri->cent,ee);
        }
        if (els) {
            FwdBemSolution* sol = (FwdBemSolution*)els->user_data;
            solution = sol->solution;
            nsol     = sol->ncoil;
        }
        else {
            solution = m->solution;
            nsol     = all_surfs ? m->nsol : m->surfs[0]->ntri;
        }
        for (k = 0; k < nsol; k++)
            grad[k] = mne_dot_vectors_40(solution[k],v0,m->nsol);
    }
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_lin_pot_calc(float *rd, float *Q, FwdBemModel *m, FwdCoilSet *els, int all_surfs, float *pot)              /* Put the result here */
/*
* Compute the potentials due to a current dipole
* using the linear potential approximation
*/
{
    float **rr;
    int   np;
    int   s,k,p,nsol;
    float mult,mri_rd[3],mri_Q[3];

    float *v0;
    float **solution;

    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;

    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (s = 0, p = 0; s < m->nsurf; s++) {
        np     = m->surfs[s]->np;
        rr     = m->surfs[s]->rr;
        mult   = m->source_mult[s];
        for (k = 0; k < np; k++)
            v0[p++] = mult*fwd_bem_inf_pot(mri_rd,mri_Q,rr[k]);
    }
    if (els) {
        FwdBemSolution* sol = (FwdBemSolution*)els->user_data;
        solution = sol->solution;
        nsol     = sol->ncoil;
    }
    else {
        solution = m->solution;
        nsol     = all_surfs ? m->nsol : m->surfs[0]->np;
    }
    for (k = 0; k < nsol; k++)
        pot[k] = mne_dot_vectors_40(solution[k],v0,m->nsol);
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_lin_pot_grad_calc(float *rd, float *Q, FwdBemModel *m, FwdCoilSet *els, int all_surfs, float *xgrad, float *ygrad, float *zgrad)
/*
* Compute the derivaties of potentials due to a current dipole with respect to the dipole position
* using the linear potential approximation
*/
{
    float **rr;
    int   np;
    int   s,k,p,nsol,pp;
    float mult,mri_rd[3],mri_Q[3];

    float *v0,ee[3];
    float **solution;

    float  *grads[3];
    float  *grad;

    grads[0] = xgrad;
    grads[1] = ygrad;
    grads[2] = zgrad;

    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;

    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (pp = 0; pp < 3; pp++) {
        grad = grads[pp];

        for (p = 0; p < 3; p++)
            ee[p] = p == pp ? 1.0 : 0.0;
        if (m->head_mri_t)
            FiffCoordTransOld::fiff_coord_trans(ee,m->head_mri_t,FIFFV_NO_MOVE);

        for (s = 0, p = 0; s < m->nsurf; s++) {
            np     = m->surfs[s]->np;
            rr     = m->surfs[s]->rr;
            mult   = m->source_mult[s];
            for (k = 0; k < np; k++)
                v0[p++] = mult*fwd_bem_inf_pot_der(mri_rd,mri_Q,rr[k],ee);
        }
        if (els) {
            FwdBemSolution* sol = (FwdBemSolution*)els->user_data;
            solution = sol->solution;
            nsol     = sol->ncoil;
        }
        else {
            solution = m->solution;
            nsol     = all_surfs ? m->nsol : m->surfs[0]->np;
        }
        for (k = 0; k < nsol; k++)
            grad[k] = mne_dot_vectors_40(solution[k],v0,m->nsol);
    }
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_pot_calc(float *rd, float *Q, FwdBemModel *m, FwdCoilSet *els, int all_surfs, float *pot)
/*
          * Compute the potentials due to a current dipole
          */
{
    MneTriangle* tri;
    int         ntri;
    int         s,k,p,nsol;
    float       mult;
    float       *v0;
    float       **solution;
    float       mri_rd[3],mri_Q[3];

    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;

    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (s = 0, p = 0; s < m->nsurf; s++) {
        ntri = m->surfs[s]->ntri;
        tri  = m->surfs[s]->tris;
        mult = m->source_mult[s];
        for (k = 0; k < ntri; k++, tri++)
            v0[p++] = mult*fwd_bem_inf_pot(mri_rd,mri_Q,tri->cent);
    }
    if (els) {
        FwdBemSolution* sol = (FwdBemSolution*)els->user_data;
        solution = sol->solution;
        nsol     = sol->ncoil;
    }
    else {
        solution = m->solution;
        nsol     = all_surfs ? m->nsol : m->surfs[0]->ntri;
    }
    for (k = 0; k < nsol; k++)
        pot[k] = mne_dot_vectors_40(solution[k],v0,m->nsol);
    return;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_pot_els(float *rd, float *Q, FwdCoilSet *els, float *pot, void *client) /* The model */
/*
     * This version calculates the potential on all surfaces
     */
{
    FwdBemModel*    m = (FwdBemModel*)client;
    FwdBemSolution* sol = (FwdBemSolution*)els->user_data;

    if (!m) {
        printf("No BEM model specified to fwd_bem_pot_els");
        return FAIL;
    }
    if (!m->solution) {
        printf("No solution available for fwd_bem_pot_els");
        return FAIL;
    }
    if (!sol || sol->ncoil != els->ncoil) {
        printf("No appropriate electrode-specific data available in fwd_bem_pot_coils");
        return FAIL;
    }
    if (m->bem_method == FWD_BEM_CONSTANT_COLL)
        fwd_bem_pot_calc(rd,Q,m,els,FALSE,pot);
    else if (m->bem_method == FWD_BEM_LINEAR_COLL)
        fwd_bem_lin_pot_calc(rd,Q,m,els,FALSE,pot);
    else {
        printf("Unknown BEM method : %d",m->bem_method);
        return FAIL;
    }
    return OK;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_pot_grad_els(float *rd, float *Q, FwdCoilSet *els, float *pot, float *xgrad, float *ygrad, float *zgrad, void *client) /* The model */
/*
     * This version calculates the potential on all surfaces
     */
{
    FwdBemModel*    m = (FwdBemModel*)client;
    FwdBemSolution* sol = (FwdBemSolution*)els->user_data;

    if (!m) {
        qCritical("No BEM model specified to fwd_bem_pot_els");
        return FAIL;
    }
    if (!m->solution) {
        qCritical("No solution available for fwd_bem_pot_els");
        return FAIL;
    }
    if (!sol || sol->ncoil != els->ncoil) {
        qCritical("No appropriate electrode-specific data available in fwd_bem_pot_coils");
        return FAIL;
    }
    if (m->bem_method == FWD_BEM_CONSTANT_COLL) {
        if (pot)
            fwd_bem_pot_calc(rd,Q,m,els,FALSE,pot);
        fwd_bem_pot_grad_calc(rd,Q,m,els,FALSE,xgrad,ygrad,zgrad);
    }
    else if (m->bem_method == FWD_BEM_LINEAR_COLL) {
        if (pot)
            fwd_bem_lin_pot_calc(rd,Q,m,els,FALSE,pot);
        fwd_bem_lin_pot_grad_calc(rd,Q,m,els,FALSE,xgrad,ygrad,zgrad);
    }
    else {
        qCritical("Unknown BEM method : %d",m->bem_method);
        return FAIL;
    }
    return OK;
}

//*************************************************************************************************************

#define ARSINH(x) log((x) + sqrt(1.0+(x)*(x)))

void FwdBemModel::calc_f(double *xx, double *yy, double *f0, double *fx, double *fy)	        /* The weights in the linear approximation */
{
    double det = -xx[Y_40]*yy[X_40] + xx[Z_40]*yy[X_40] +
            xx[X_40]*yy[Y_40] - xx[Z_40]*yy[Y_40] - xx[X_40]*yy[Z_40] + xx[Y_40]*yy[Z_40];
    int k;

    f0[X_40] = -xx[Z_40]*yy[Y_40] + xx[Y_40]*yy[Z_40];
    f0[Y_40] = xx[Z_40]*yy[X_40] - xx[X_40]*yy[Z_40];
    f0[Z_40] = -xx[Y_40]*yy[X_40] + xx[X_40]*yy[Y_40];

    fx[X_40] =  yy[Y_40] - yy[Z_40];
    fx[Y_40] = -yy[X_40] + yy[Z_40];
    fx[Z_40] = yy[X_40] - yy[Y_40];

    fy[X_40] = -xx[Y_40] + xx[Z_40];
    fy[Y_40] = xx[X_40] - xx[Z_40];
    fy[Z_40] = -xx[X_40] + xx[Y_40];

    for (k = 0; k < 3; k++) {
        f0[k] = f0[k]/det;
        fx[k] = fx[k]/det;
        fy[k] = fy[k]/det;
    }
}

//*************************************************************************************************************

void FwdBemModel::calc_magic(double u, double z, double A, double B, double *beta, double *D)
/*
* Calculate Urankar's magic numbers
*/
{
    double B2 = 1.0 + B*B;
    double ABu = A + B*u;
    *D = sqrt(u*u + z*z + ABu*ABu);
    beta[0] = ABu/sqrt(u*u + z*z);
    beta[1] = (A*B + B2*u)/sqrt(A*A + B2*z*z);
    beta[2] = (B*z*z - A*u)/(z*(*D));
}

//*************************************************************************************************************

void FwdBemModel::field_integrals(float *from, MneTriangle* to, double *I1p, double *T, double *S1, double *S2, double *f0, double *fx, double *fy)
{
    double y1[3],y2[3],y3[3];
    double xx[4],yy[4];
    double A,B,z,dx;
    double beta[3],I1,Tx,Ty,Txx,Tyy,Sxx,mult;
    double S1x,S1y,S2x,S2y;
    double D1,B2;
    int k;
    /*
       * Preliminaries...
       *
       * 1. Move origin to viewpoint...
       *
       */
    VEC_DIFF_40(from,to->r1,y1);
    VEC_DIFF_40(from,to->r2,y2);
    VEC_DIFF_40(from,to->r3,y3);
    /*
       * 2. Calculate local xy coordinates...
       */
    xx[0] = VEC_DOT_40(y1,to->ex);
    xx[1] = VEC_DOT_40(y2,to->ex);
    xx[2] = VEC_DOT_40(y3,to->ex);
    xx[3] = xx[0];

    yy[0] = VEC_DOT_40(y1,to->ey);
    yy[1] = VEC_DOT_40(y2,to->ey);
    yy[2] = VEC_DOT_40(y3,to->ey);
    yy[3] = yy[0];

    calc_f (xx,yy,f0,fx,fy);
    /*
       * 3. Distance of the plane from origin...
       */
    z = VEC_DOT_40(y1,to->nn);
    /*
       * Put together the line integral...
       * We use the convention where the local y-axis
       * is parallel to the last side and, therefore, dx = 0
       * on that side. We can thus omit the last side from this
       * computation in some cases.
       */
    I1 = 0.0;
    Tx = 0.0;
    Ty = 0.0;
    S1x = 0.0;
    S1y = 0.0;
    S2x = 0.0;
    S2y = 0.0;
    for (k = 0; k < 2; k++) {
        dx = xx[k+1] - xx[k];
        A = (yy[k]*xx[k+1] - yy[k+1]*xx[k])/dx;
        B = (yy[k+1]-yy[k])/dx;
        B2 = (1.0 + B*B);
        /*
         * Upper limit
         */
        calc_magic (xx[k+1],z,A,B,beta,&D1);
        I1 = I1 - xx[k+1]*ARSINH(beta[0]) - (A/sqrt(1.0+B*B))*ARSINH(beta[1])
                - z*atan(beta[2]);
        Txx = ARSINH(beta[1])/sqrt(B2);
        Tx = Tx + Txx;
        Ty = Ty + B*Txx;
        Sxx = (D1 - A*B*Txx)/B2;
        S1x = S1x + Sxx;
        S1y = S1y + B*Sxx;
        Sxx = (B*D1 + A*Txx)/B2;
        S2x = S2x + Sxx;
        /*
         * Lower limit
         */
        calc_magic (xx[k],z,A,B,beta,&D1);
        I1 = I1 + xx[k]*ARSINH(beta[0]) + (A/sqrt(1.0+B*B))*ARSINH(beta[1])
                + z*atan(beta[2]);
        Txx = ARSINH(beta[1])/sqrt(B2);
        Tx = Tx - Txx;
        Ty = Ty - B*Txx;
        Sxx = (D1 - A*B*Txx)/B2;
        S1x = S1x - Sxx;
        S1y = S1y - B*Sxx;
        Sxx = (B*D1 + A*Txx)/B2;
        S2x = S2x - Sxx;
    }
    /*
       * Handle last side (dx = 0) in a special way;
       */
    mult = 1.0/sqrt(xx[k]*xx[k]+z*z);
    /*
       * Upper...
       */
    Tyy = ARSINH(mult*yy[k+1]);
    Ty = Ty + Tyy;
    S1y = S1y + xx[k]*Tyy;
    /*
       * Lower...
       */
    Tyy = ARSINH(mult*yy[k]);
    Ty = Ty - Tyy;
    S1y = S1y - xx[k]*Tyy;
    /*
       * Set return values
       */
    *I1p = I1;
    T[X_40] = Tx;
    T[Y_40] = Ty;
    S1[X_40] = S1x;
    S1[Y_40] = S1y;
    S2[X_40] = S2x;
    S2[Y_40] = -S1x;
    return;
}

//*************************************************************************************************************

double FwdBemModel::one_field_coeff(float *dest, float *normal, MneTriangle* tri)
/*
* Compute the integral over one triangle.
* This looks magical but it is not.
*/
{
    double *yy[4];
    double y1[3],y2[3],y3[3];
    double beta[3];
    double bbeta[3];
    double coeff[3];
    int   j,k;

    yy[0] = y1;
    yy[1] = y2;
    yy[2] = y3;
    yy[3] = y1;
    VEC_DIFF_40(dest,tri->r1,y1);
    VEC_DIFF_40(dest,tri->r2,y2);
    VEC_DIFF_40(dest,tri->r3,y3);
    for (j = 0; j < 3; j++)
        beta[j] = calc_beta(yy[j],yy[j+1]);
    bbeta[0] = beta[2] - beta[0];
    bbeta[1] = beta[0] - beta[1];
    bbeta[2] = beta[1] - beta[2];

    for (j = 0; j < 3; j++)
        coeff[j] = 0.0;
    for (j = 0; j < 3; j++)
        for (k = 0; k < 3; k++)
            coeff[k] = coeff[k] + yy[j][k]*bbeta[j];
    return (VEC_DOT_40(coeff,normal));
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_field_coeff(FwdBemModel *m, FwdCoilSet *coils)	/* Gradiometer coil positions */
/*
     * Compute the weighting factors to obtain the magnetic field
     */
{
    MneSurfaceOld*     surf;
    MneTriangle*    tri;
    FwdCoil*        coil;
    FwdCoilSet*     tcoils = NULL;
    int            ntri;
    float          **coeff = NULL;
    int            j,k,p,s,off;
    double         res;
    double         mult;

    if (m->solution == NULL) {
        printf("Solution matrix missing in fwd_bem_field_coeff");
        return NULL;
    }
    if (m->bem_method != FWD_BEM_CONSTANT_COLL) {
        printf("BEM method should be constant collocation for fwd_bem_field_coeff");
        return NULL;
    }
    if (coils->coord_frame != FIFFV_COORD_MRI) {
        if (coils->coord_frame == FIFFV_COORD_HEAD) {
            if (!m->head_mri_t) {
                printf("head -> mri coordinate transform missing in fwd_bem_field_coeff");
                return NULL;
            }
            else {
                if (!coils) {
                    qWarning("No coils to duplicate");
                    return NULL;
                }
                /*
                    * Make a transformed duplicate
                    */
                if ((tcoils = coils->dup_coil_set(m->head_mri_t)) == NULL)
                    return NULL;
                coils = tcoils;
            }
        }
        else {
            printf("Incompatible coil coordinate frame %d for fwd_bem_field_coeff",coils->coord_frame);
            return NULL;
        }
    }
    ntri  = m->nsol;
    coeff = ALLOC_CMATRIX_40(coils->ncoil,ntri);

    for (s = 0, off = 0; s < m->nsurf; s++) {
        surf = m->surfs[s];
        ntri = surf->ntri;
        tri  = surf->tris;
        mult = m->field_mult[s];

        for (k = 0; k < ntri; k++,tri++) {
            for (j = 0; j < coils->ncoil; j++) {
                coil = coils->coils[j];
                res = 0.0;
                for (p = 0; p < coil->np; p++)
                    res = res + coil->w[p]*one_field_coeff(coil->rmag[p],coil->cosmag[p],tri);
                coeff[j][k+off] = mult*res;
            }
        }
        off = off + ntri;
    }
    delete tcoils;
    return coeff;
}

//*************************************************************************************************************

double FwdBemModel::calc_gamma(double *rk, double *rk1)
{
    double rkk1[3];
    double size;
    double res;

    VEC_DIFF_40(rk,rk1,rkk1);
    size = VEC_LEN_40(rkk1);

    res = log((VEC_LEN_40(rk1)*size + VEC_DOT_40(rk1,rkk1))/
              (VEC_LEN_40(rk)*size + VEC_DOT_40(rk,rkk1)))/size;
    return (res);
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_one_lin_field_coeff_ferg(float *dest, float *dir, MneTriangle* tri, double *res)	/* The results */
{
    double c[3];			/* Component of dest vector normal to
                                     * the triangle plane */
    double A[3];			/* Projection of dest onto the triangle */
    double c1[3],c2[3],c3[3];
    double y1[3],y2[3],y3[3];
    double *yy[4],*cc[4];
    double rjk[3][3];
    double cross[3],triple,l1,l2,l3,solid,clen;
    double common,sum,beta,gamma;
    int    k;

    yy[0] = y1;   cc[0] = c1;
    yy[1] = y2;   cc[1] = c2;
    yy[2] = y3;   cc[2] = c3;
    yy[3] = y1;   cc[3] = c1;

    VEC_DIFF_40(tri->r2,tri->r3,rjk[0]);
    VEC_DIFF_40(tri->r3,tri->r1,rjk[1]);
    VEC_DIFF_40(tri->r1,tri->r2,rjk[2]);

    for (k = 0; k < 3; k++) {
        y1[k] = tri->r1[k] - dest[k];
        y2[k] = tri->r2[k] - dest[k];
        y3[k] = tri->r3[k] - dest[k];
    }
    clen  = VEC_DOT_40(y1,tri->nn);
    for (k = 0; k < 3; k++) {
        c[k]  = clen*tri->nn[k];
        A[k]  = dest[k] + c[k];
        c1[k] = tri->r1[k] - A[k];
        c2[k] = tri->r2[k] - A[k];
        c3[k] = tri->r3[k] - A[k];
    }
    /*
       * beta and gamma...
       */
    for (sum = 0.0, k = 0; k < 3; k++) {
        CROSS_PRODUCT_40(cc[k],cc[k+1],cross);
        beta  = VEC_DOT_40(cross,tri->nn);
        gamma = calc_gamma (yy[k],yy[k+1]);
        sum = sum + beta*gamma;
    }
    /*
       * Solid angle...
       */
    CROSS_PRODUCT_40(y1,y2,cross);
    triple = VEC_DOT_40(cross,y3);

    l1 = VEC_LEN_40(y1);
    l2 = VEC_LEN_40(y2);
    l3 = VEC_LEN_40(y3);
    solid = 2.0*atan2(triple,
                      (l1*l2*l3+
                       VEC_DOT_40(y1,y2)*l3+
                       VEC_DOT_40(y1,y3)*l2+
                       VEC_DOT_40(y2,y3)*l1));
    /*
       * Now we are ready to assemble it all together
       */
    common = (sum-clen*solid)/(2.0*tri->area);
    for (k = 0; k < 3; k++)
        res[k] = -VEC_DOT_40(rjk[k],dir)*common;
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_one_lin_field_coeff_uran(float *dest, float *dir, MneTriangle* tri, double *res)	/* The results */
{
    double      I1,T[2],S1[2],S2[2];
    double      f0[3],fx[3],fy[3];
    double      res_x,res_y;
    double      x_fac,y_fac;
    int         k;
    double      len;
    /*
       * Compute the component integrals
       */
    field_integrals (dest,tri,&I1,T,S1,S2,f0,fx,fy);
    /*
       * Compute the coefficient for each node...
       */
    len = VEC_LEN_40(dir);
    dir[X_40] = dir[X_40]/len;
    dir[Y_40] = dir[Y_40]/len;
    dir[Z_40] = dir[Z_40]/len;

    x_fac = -VEC_DOT_40(dir,tri->ex);
    y_fac = -VEC_DOT_40(dir,tri->ey);
    for (k = 0; k < 3; k++) {
        res_x = f0[k]*T[X_40] + fx[k]*S1[X_40] + fy[k]*S2[X_40] + fy[k]*I1;
        res_y = f0[k]*T[Y_40] + fx[k]*S1[Y_40] + fy[k]*S2[Y_40] - fx[k]*I1;
        res[k] = x_fac*res_x + y_fac*res_y;
    }
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_one_lin_field_coeff_simple(float *dest, float *normal, MneTriangle* source, double *res)     /* The result for each triangle node */
/*
          * Simple version...
          */
{
    float diff[3];
    float vec_result[3];
    float dl;
    int   k;
    float *rr[3];

    rr[0] = source->r1;
    rr[1] = source->r2;
    rr[2] = source->r3;

    for (k = 0; k < 3; k++) {
        VEC_DIFF_40(rr[k],dest,diff);
        dl = VEC_DOT_40(diff,diff);
        CROSS_PRODUCT_40(diff,source->nn,vec_result);
        res[k] = source->area*VEC_DOT_40(vec_result,normal)/(3.0*dl*sqrt(dl));
    }
    return;
}

//*************************************************************************************************************

float **FwdBemModel::fwd_bem_lin_field_coeff(FwdBemModel *m, FwdCoilSet *coils, int method)    /* Which integration formula to use */
/*
          * Compute the weighting factors to obtain the magnetic field
          * in the linear potential approximation
          */
{
    MneSurfaceOld*  surf;
    MneTriangle* tri;
    FwdCoil*     coil;
    FwdCoilSet*  tcoils = NULL;
    int         ntri;
    float       **coeff  = NULL;
    int         j,k,p,pp,off,s;
    double      res[3],one[3];
    float       mult;
    linFieldIntFunc func;

    if (m->solution == NULL) {
        printf("Solution matrix missing in fwd_bem_lin_field_coeff");
        return NULL;
    }
    if (m->bem_method != FWD_BEM_LINEAR_COLL) {
        printf("BEM method should be linear collocation for fwd_bem_lin_field_coeff");
        return NULL;
    }
    if (coils->coord_frame != FIFFV_COORD_MRI) {
        if (coils->coord_frame == FIFFV_COORD_HEAD) {
            if (!m->head_mri_t) {
                printf("head -> mri coordinate transform missing in fwd_bem_lin_field_coeff");
                return NULL;
            }
            else {
                if (!coils) {
                    qWarning("No coils to duplicate");
                    return NULL;
                }
                /*
                    * Make a transformed duplicate
                    */
                if ((tcoils = coils->dup_coil_set(m->head_mri_t)) == NULL)
                    return NULL;
                coils = tcoils;
            }
        }
        else {
            printf("Incompatible coil coordinate frame %d for fwd_bem_field_coeff",coils->coord_frame);
            return NULL;
        }
    }
    if (method == FWD_BEM_LIN_FIELD_FERGUSON)
        func = fwd_bem_one_lin_field_coeff_ferg;
    else if (method == FWD_BEM_LIN_FIELD_URANKAR)
        func = fwd_bem_one_lin_field_coeff_uran;
    else
        func = fwd_bem_one_lin_field_coeff_simple;

    coeff = ALLOC_CMATRIX_40(coils->ncoil,m->nsol);
    for (k = 0; k < m->nsol; k++)
        for (j = 0; j < coils->ncoil; j++)
            coeff[j][k] = 0.0;
    /*
       * Process each of the surfaces
       */
    for (s = 0, off = 0; s < m->nsurf; s++) {
        surf = m->surfs[s];
        ntri = surf->ntri;
        tri  = surf->tris;
        mult = m->field_mult[s];

        for (k = 0; k < ntri; k++,tri++) {
            for (j = 0; j < coils->ncoil; j++) {
                coil = coils->coils[j];
                for (pp = 0; pp < 3; pp++)
                    res[pp] = 0;
                /*
             * Accumulate the coefficients for each triangle node...
             */
                for (p = 0; p < coil->np; p++) {
                    func(coil->rmag[p],coil->cosmag[p],tri,one);
                    for (pp = 0; pp < 3; pp++)
                        res[pp] = res[pp] + coil->w[p]*one[pp];
                }
                /*
             * Add these to the corresponding coefficient matrix
             * elements...
             */
                for (pp = 0; pp < 3; pp++)
                    coeff[j][tri->vert[pp]+off] = coeff[j][tri->vert[pp]+off] + mult*res[pp];
            }
        }
        off = off + surf->np;
    }
    /*
       * Discard the duplicate
       */
    delete tcoils;
    return (coeff);
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_specify_coils(FwdBemModel *m, FwdCoilSet *coils)
/*
     * Set up for computing the solution at a set of coils
      */
{
    float **sol = NULL;
    FwdBemSolution* csol;

    if (!m) {
        printf("Model missing in fwd_bem_specify_coils");
        goto bad;
    }
    if (!m->solution) {
        printf("Solution not computed in fwd_bem_specify_coils");
        goto bad;
    }
    if(coils)
        coils->fwd_free_coil_set_user_data();
    if (!coils || coils->ncoil == 0)
        return OK;
    if (m->bem_method == FWD_BEM_CONSTANT_COLL)
        sol = fwd_bem_field_coeff(m,coils);
    else if (m->bem_method == FWD_BEM_LINEAR_COLL)
        sol = fwd_bem_lin_field_coeff(m,coils,FWD_BEM_LIN_FIELD_SIMPLE);
    else {
        printf("Unknown BEM method in fwd_bem_specify_coils : %d",m->bem_method);
        goto bad;
    }
    coils->user_data = csol = new FwdBemSolution();
    coils->user_data_free   = FwdBemSolution::fwd_bem_free_coil_solution;

    csol->ncoil     = coils->ncoil;
    csol->np        = m->nsol;
    csol->solution  = mne_mat_mat_mult_40(sol,
                                          m->solution,
                                          coils->ncoil,
                                          m->nsol,
                                          m->nsol);//TODO: Suspicion, that this is slow - use Eigen

    FREE_CMATRIX_40(sol);
    return OK;

bad : {
        FREE_CMATRIX_40(sol);
        return FAIL;

    }
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_lin_field_calc(float *rd, float *Q, FwdCoilSet *coils, FwdBemModel *m, float *B)
/*
     * Calculate the magnetic field in a set of coils
     */
{
    float *v0;
    int   s,k,p,np;
    FwdCoil* coil;
    float  mult;
    float  **rr;
    float  my_rd[3],my_Q[3];
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;
    /*
       * Infinite-medium potentials
       */
    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;
    /*
       * The dipole location and orientation must be transformed
       */
    VEC_COPY_40(my_rd,rd);
    VEC_COPY_40(my_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(my_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(my_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    /*
       * Compute the inifinite-medium potentials at the vertices
       */
    for (s = 0, p = 0; s < m->nsurf; s++) {
        np     = m->surfs[s]->np;
        rr     = m->surfs[s]->rr;
        mult   = m->source_mult[s];
        for (k = 0; k < np; k++)
            v0[p++] = mult*fwd_bem_inf_pot(my_rd,my_Q,rr[k]);
    }
    /*
       * Primary current contribution
       * (can be calculated in the coil/dipole coordinates)
       */
    for (k = 0; k < coils->ncoil; k++) {
        coil = coils->coils[k];
        B[k] = 0.0;
        for (p = 0; p < coil->np; p++)
            B[k] = B[k] + coil->w[p]*fwd_bem_inf_field(rd,Q,coil->rmag[p],coil->cosmag[p]);
    }
    /*
       * Volume current contribution
       */
    for (k = 0; k < coils->ncoil; k++)
        B[k] = B[k] + mne_dot_vectors_40(sol->solution[k],v0,m->nsol);
    /*
       * Scale correctly
       */
    for (k = 0; k < coils->ncoil; k++)
        B[k] = MAG_FACTOR*B[k];
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_field_calc(float *rd, float *Q, FwdCoilSet *coils, FwdBemModel *m, float *B)
/*
     * Calculate the magnetic field in a set of coils
     */
{
    float *v0;
    int   s,k,p,ntri;
    FwdCoil* coil;
    MneTriangle* tri;
    float   mult;
    float  my_rd[3],my_Q[3];
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;
    /*
       * Infinite-medium potentials
       */
    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;
    /*
       * The dipole location and orientation must be transformed
       */
    VEC_COPY_40(my_rd,rd);
    VEC_COPY_40(my_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(my_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(my_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    /*
       * Compute the inifinite-medium potentials at the centers of the triangles
       */
    for (s = 0, p = 0; s < m->nsurf; s++) {
        ntri = m->surfs[s]->ntri;
        tri  = m->surfs[s]->tris;
        mult = m->source_mult[s];
        for (k = 0; k < ntri; k++, tri++)
            v0[p++] = mult*fwd_bem_inf_pot(my_rd,my_Q,tri->cent);
    }
    /*
       * Primary current contribution
       * (can be calculated in the coil/dipole coordinates)
       */
    for (k = 0; k < coils->ncoil; k++) {
        coil = coils->coils[k];
        B[k] = 0.0;
        for (p = 0; p < coil->np; p++)
            B[k] = B[k] + coil->w[p]*fwd_bem_inf_field(rd,Q,coil->rmag[p],coil->cosmag[p]);
    }
    /*
       * Volume current contribution
       */
    for (k = 0; k < coils->ncoil; k++)
        B[k] = B[k] + mne_dot_vectors_40(sol->solution[k],v0,m->nsol);
    /*
       * Scale correctly
       */
    for (k = 0; k < coils->ncoil; k++)
        B[k] = MAG_FACTOR*B[k];
    return;
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_field_grad_calc(float *rd, float *Q, FwdCoilSet* coils, FwdBemModel* m, float *xgrad, float *ygrad, float *zgrad)
/*
* Calculate the magnetic field in a set of coils
*/
{
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;
    float          *v0;
    int            s,k,p,ntri,pp;
    FwdCoil*       coil;
    MneTriangle*   tri;
    float          mult;
    float          *grads[3],ee[3],mri_ee[3],mri_rd[3],mri_Q[3];
    float          *grad;

    grads[0] = xgrad;
    grads[1] = ygrad;
    grads[2] = zgrad;
    /*
       * Infinite-medium potentials
       */
    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;
    /*
       * The dipole location and orientation must be transformed
       */
    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (pp = 0; pp < 3; pp++) {
        grad = grads[pp];
        /*
         * Select the correct gradient component
         */
        for (p = 0; p < 3; p++)
            ee[p] = p == pp ? 1.0 : 0.0;
        VEC_COPY_40(mri_ee,ee);
        if (m->head_mri_t)
            FiffCoordTransOld::fiff_coord_trans(mri_ee,m->head_mri_t,FIFFV_NO_MOVE);
        /*
         * Compute the inifinite-medium potential derivatives at the centers of the triangles
         */
        for (s = 0, p = 0; s < m->nsurf; s++) {
            ntri = m->surfs[s]->ntri;
            tri  = m->surfs[s]->tris;
            mult = m->source_mult[s];
            for (k = 0; k < ntri; k++, tri++) {
                v0[p++] = mult*fwd_bem_inf_pot_der(mri_rd,mri_Q,tri->cent,mri_ee);
            }
        }
        /*
         * Primary current contribution
         * (can be calculated in the coil/dipole coordinates)
         */
        for (k = 0; k < coils->ncoil; k++) {
            coil = coils->coils[k];
            grad[k] = 0.0;
            for (p = 0; p < coil->np; p++)
                grad[k] = grad[k] + coil->w[p]*fwd_bem_inf_field_der(rd,Q,coil->rmag[p],coil->cosmag[p],ee);
        }
        /*
         * Volume current contribution
         */
        for (k = 0; k < coils->ncoil; k++)
            grad[k] = grad[k] + mne_dot_vectors_40(sol->solution[k],v0,m->nsol);
        /*
         * Scale correctly
         */
        for (k = 0; k < coils->ncoil; k++)
            grad[k] = MAG_FACTOR*grad[k];
    }
    return;
}

//*************************************************************************************************************

float FwdBemModel::fwd_bem_inf_field_der(float *rd, float *Q, float *rp, float *dir, float *comp)	   /* Which gradient component */
/*
* Derivative of the infinite-medium magnetic field with respect to
* one of the dipole position coordinates (without \mu_0/4\pi)
*/
{
    float diff[3],diff2,diff3,diff5,cross[3],crossn[3],res;

    VEC_DIFF_40(rd,rp,diff);
    diff2 = VEC_DOT_40(diff,diff);
    diff3 = sqrt(diff2)*diff2;
    diff5 = diff3*diff2;
    CROSS_PRODUCT_40(Q,diff,cross);
    CROSS_PRODUCT_40(dir,Q,crossn);

    res = 3*VEC_DOT_40(cross,dir)*VEC_DOT_40(comp,diff)/diff5 - VEC_DOT_40(comp,crossn)/diff3;
    return res;
}

//*************************************************************************************************************

float FwdBemModel::fwd_bem_inf_pot_der(float *rd, float *Q, float *rp, float *comp) /* Which gradient component */
/*
* Derivative of the infinite-medium potential with respect to one of
* the dipole position coordinates
*/
{
    float diff[3];
    float diff2,diff5,diff3;
    float res;

    VEC_DIFF_40(rd,rp,diff);
    diff2 = VEC_DOT_40(diff,diff);
    diff3 = sqrt(diff2)*diff2;
    diff5 = diff3*diff2;

    res = 3*VEC_DOT_40(Q,diff)*VEC_DOT_40(comp,diff)/diff5 - VEC_DOT_40(comp,Q)/diff3;
    return (res/(4.0*M_PI));
}

//*************************************************************************************************************

void FwdBemModel::fwd_bem_lin_field_grad_calc(float *rd, float *Q, FwdCoilSet *coils, FwdBemModel *m, float *xgrad, float *ygrad, float *zgrad)
/*
     * Calculate the gradient with respect to dipole position coordinates in a set of coils
     */
{
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;

    float   *v0;
    int     s,k,p,np,pp;
    FwdCoil *coil;
    float   mult;
    float   **rr,ee[3],mri_ee[3],mri_rd[3],mri_Q[3];
    float   *grads[3];
    float   *grad;

    grads[0] = xgrad;
    grads[1] = ygrad;
    grads[2] = zgrad;
    /*
       * Space for infinite-medium potentials
       */
    if (!m->v0)
        m->v0 = MALLOC_40(m->nsol,float);
    v0 = m->v0;
    /*
       * The dipole location and orientation must be transformed
       */
    VEC_COPY_40(mri_rd,rd);
    VEC_COPY_40(mri_Q,Q);
    if (m->head_mri_t) {
        FiffCoordTransOld::fiff_coord_trans(mri_rd,m->head_mri_t,FIFFV_MOVE);
        FiffCoordTransOld::fiff_coord_trans(mri_Q,m->head_mri_t,FIFFV_NO_MOVE);
    }
    for (pp = 0; pp < 3; pp++) {
        grad = grads[pp];
        /*
         * Select the correct gradient component
         */
        for (p = 0; p < 3; p++)
            ee[p] = p == pp ? 1.0 : 0.0;
        VEC_COPY_40(mri_ee,ee);
        if (m->head_mri_t)
            FiffCoordTransOld::fiff_coord_trans(mri_ee,m->head_mri_t,FIFFV_NO_MOVE);
        /*
         * Compute the inifinite-medium potentials at the vertices
         */
        for (s = 0, p = 0; s < m->nsurf; s++) {
            np     = m->surfs[s]->np;
            rr     = m->surfs[s]->rr;
            mult   = m->source_mult[s];

            for (k = 0; k < np; k++)
                v0[p++] = mult*fwd_bem_inf_pot_der(mri_rd,mri_Q,rr[k],mri_ee);
        }
        /*
         * Primary current contribution
         * (can be calculated in the coil/dipole coordinates)
         */
        for (k = 0; k < coils->ncoil; k++) {
            coil = coils->coils[k];
            grad[k] = 0.0;
            for (p = 0; p < coil->np; p++)
                grad[k] = grad[k] + coil->w[p]*fwd_bem_inf_field_der(rd,Q,coil->rmag[p],coil->cosmag[p],ee);
        }
        /*
         * Volume current contribution
         */
        for (k = 0; k < coils->ncoil; k++)
            grad[k] = grad[k] + mne_dot_vectors_40(sol->solution[k],v0,m->nsol);
        /*
         * Scale correctly
         */
        for (k = 0; k < coils->ncoil; k++)
            grad[k] = MAG_FACTOR*grad[k];
    }
    return;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_field(float *rd, float *Q, FwdCoilSet *coils, float *B, void *client)  /* The model */
/*
     * This version calculates the magnetic field in a set of coils
     * Call fwd_bem_specify_coils first to establish the coil-specific
     * solution matrix
     */
{
    FwdBemModel* m = (FwdBemModel*)client;
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;

    if (!m) {
        printf("No BEM model specified to fwd_bem_field");
        return FAIL;
    }
    if (!sol || !sol->solution || sol->ncoil != coils->ncoil) {
        printf("No appropriate coil-specific data available in fwd_bem_field");
        return FAIL;
    }
    if (m->bem_method == FWD_BEM_CONSTANT_COLL)
        fwd_bem_field_calc(rd,Q,coils,m,B);
    else if (m->bem_method == FWD_BEM_LINEAR_COLL)
        fwd_bem_lin_field_calc(rd,Q,coils,m,B);
    else {
        printf("Unknown BEM method : %d",m->bem_method);
        return FAIL;
    }
    return OK;
}

//*************************************************************************************************************

int FwdBemModel::fwd_bem_field_grad(float *rd, float Q[], FwdCoilSet *coils, float Bval[], float xgrad[], float ygrad[], float zgrad[], void *client)  /* Client data to be passed to some foward modelling routines */
{
    FwdBemModel* m = (FwdBemModel*)client;
    FwdBemSolution* sol = (FwdBemSolution*)coils->user_data;

    if (!m) {
        qCritical("No BEM model specified to fwd_bem_field");
        return FAIL;
    }
    if (!sol || !sol->solution || sol->ncoil != coils->ncoil) {
        qCritical("No appropriate coil-specific data available in fwd_bem_field");
        return FAIL;
    }
    if (m->bem_method == FWD_BEM_CONSTANT_COLL) {
        if (Bval)
            fwd_bem_field_calc(rd,Q,coils,m,Bval);
        fwd_bem_field_grad_calc(rd,Q,coils,m,xgrad,ygrad,zgrad);
    }
    else if (m->bem_method == FWD_BEM_LINEAR_COLL) {
        if (Bval)
            fwd_bem_lin_field_calc(rd,Q,coils,m,Bval);
        fwd_bem_lin_field_grad_calc(rd,Q,coils,m,xgrad,ygrad,zgrad);
    }
    else {
        qCritical("Unknown BEM method : %d",m->bem_method);
        return FAIL;
    }
    return OK;

}

//*************************************************************************************************************

void *FwdBemModel::meg_eeg_fwd_one_source_space(void *arg)
/*
* Compute the MEG or EEG forward solution for one source space
* and possibly for only one source component
*/
{
    FwdThreadArg* a = (FwdThreadArg*)arg;
    MneSourceSpaceOld* s = a->s;
    int            j,p,q;
    float          *xyz[3];

    p = a->off;
    q = 3*a->off;
    if (a->fixed_ori) {					  /* The normal source component only */
        if (a->field_pot_grad && a->res_grad) {                   /* Gradient requested? */
            for (j = 0; j < s->np; j++)
                if (s->inuse[j]) {
                    if (a->field_pot_grad(s->rr[j],s->nn[j],a->coils_els,a->res[p],
                                          a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                          a->client) != OK)
                        goto bad;
                    q = q + 3;
                    p++;
                }
        }
        else {
            for (j = 0; j < s->np; j++)
                if (s->inuse[j])
                    if (a->field_pot(s->rr[j],s->nn[j],a->coils_els,a->res[p++],a->client) != OK)
                        goto bad;
        }
    }
    else {						  /* All source components */
        if (a->field_pot_grad && a->res_grad) {               /* Gradient requested? */
            for (j = 0; j < s->np; j++) {
                if (s->inuse[j]) {
                    if (a->comp < 0) {				  /* Compute all components */
                        if (a->field_pot_grad(s->rr[j],Qx,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                        if (a->field_pot_grad(s->rr[j],Qy,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                        if (a->field_pot_grad(s->rr[j],Qz,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                    }
                    else if (a->comp == 0) {			  /* Compute x component */
                        if (a->field_pot_grad(s->rr[j],Qx,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                        q = q + 3; p++;
                        q = q + 3; p++;
                    }
                    else if (a->comp == 1) {			  /* Compute y component */
                        q = q + 3; p++;
                        if (a->field_pot_grad(s->rr[j],Qy,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                        q = q + 3; p++;
                    }
                    else if (a->comp == 2) {			  /* Compute z component */
                        q = q + 3; p++;
                        q = q + 3; p++;
                        if (a->field_pot_grad(s->rr[j],Qz,a->coils_els,a->res[p],
                                              a->res_grad[q],a->res_grad[q+1],a->res_grad[q+2],
                                              a->client) != OK)
                            goto bad;
                        q = q + 3; p++;
                    }
                }
            }
        }
        else {
            for (j = 0; j < s->np; j++) {
                if (s->inuse[j]) {
                    if (a->vec_field_pot) {
                        xyz[0] = a->res[p++];
                        xyz[1] = a->res[p++];
                        xyz[2] = a->res[p++];
                        if (a->vec_field_pot(s->rr[j],a->coils_els,xyz,a->client) != OK)
                            goto bad;
                    }
                    else {
                        if (a->comp < 0) {				  /* Compute all components here */
                            if (a->field_pot(s->rr[j],Qx,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                            if (a->field_pot(s->rr[j],Qy,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                            if (a->field_pot(s->rr[j],Qz,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                        }
                        else if (a->comp == 0) {			  /* Compute x component */
                            if (a->field_pot(s->rr[j],Qx,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                            p++; p++;
                        }
                        else if (a->comp == 1) {			  /* Compute y component */
                            p++;
                            if (a->field_pot(s->rr[j],Qy,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                            p++;
                        }
                        else if (a->comp == 2) {			  /* Compute z component */
                            p++; p++;
                            if (a->field_pot(s->rr[j],Qz,a->coils_els,a->res[p++],a->client) != OK)
                                goto bad;
                        }
                    }
                }
            }
        }
    }
    a->stat = OK;
    return NULL;

bad : {
        a->stat = FAIL;
        return NULL;
    }
}

//*************************************************************************************************************

int FwdBemModel::compute_forward_meg(MneSourceSpaceOld **spaces,
                                     int nspace,
                                     FwdCoilSet *coils,
                                     FwdCoilSet *comp_coils,
                                     MneCTFCompDataSet *comp_data,
                                     bool fixed_ori,
                                     FwdBemModel *bem_model,
                                     Vector3f *r0,
                                     bool use_threads,
                                     MneNamedMatrix **resp,
                                     MneNamedMatrix **resp_grad)
/*
* Compute the MEG forward solution
* Use either the sphere model or BEM in the calculations
*/
{
    float               **res = NULL;       /* The forward solution matrix */
    float               **res_grad = NULL;  /* The gradient with respect to the dipole position */
    FwdCompData         *comp = NULL;
    fwdFieldFunc        field;              /* Computes the field for one dipole orientation */
    fwdVecFieldFunc     vec_field;          /* Computes the field for all dipole orientations */
    fwdFieldGradFunc    field_grad;         /* Computes the field and gradient with respect to dipole position
                                             * for one dipole orientation */
    int                 nmeg = coils->ncoil;/* Number of channels */
    int                 nsource;            /* Total number of sources */
    int                 k,p,q,off;
    QStringList         names;              /* Channel names */
    void                *client;
    FwdThreadArg*       one_arg = NULL;
    int                 nproc = QThread::idealThreadCount();
    QStringList         emptyList;

    if (bem_model) {
        /*
         * Use the new compensated field computation
         * It works the same way independent of whether or not the compensation is in effect
         */
#ifdef TEST
        fprintf(stderr,"Using differences.\n");
        comp = FwdCompData::fwd_make_comp_data(comp_data,coils,comp_coils,
                                               FwdBemModel::fwd_bem_field,NULL,my_bem_field_grad,bem_model,NULL);
#else
        comp = FwdCompData::fwd_make_comp_data(comp_data,coils,comp_coils,
                                               FwdBemModel::fwd_bem_field,NULL,FwdBemModel::fwd_bem_field_grad,bem_model,NULL);
#endif
        if (!comp)
            goto bad;
        /*
        * Field computation matrices...
        */
        qDebug() << "!!!TODO Speed the following with Eigen up!";
        printf("Composing the field computation matrix...");
        if (fwd_bem_specify_coils(bem_model,coils) == FAIL)
            goto bad;
        fprintf(stderr,"[done]\n");

        if (comp->set && comp->set->current) { /* Test just to specify confusing output */
            fprintf(stderr,"Composing the field computation matrix (compensation coils)...");
            if (fwd_bem_specify_coils(bem_model,comp->comp_coils) == FAIL)
                goto bad;
            fprintf(stderr,"[done]\n");
        }
        field      = FwdCompData::fwd_comp_field;
        vec_field  = NULL;
        field_grad = FwdCompData::fwd_comp_field_grad;
        client     = comp;
    }
    else {
        /*
         * Use the new compensated field computation
         * It works the same way independent of whether or not the compensation is in effect
         */
#ifdef TEST
        fprintf(stderr,"Using differences.\n");
        comp = FwdCompData::fwd_make_comp_data(comp_data,coils,comp_coils,
                                               fwd_sphere_field,
                                               fwd_sphere_field_vec,
                                               my_sphere_field_grad,
                                               r0,NULL);
#else
        comp = FwdCompData::fwd_make_comp_data(comp_data,coils,comp_coils,
                                               fwd_sphere_field,
                                               fwd_sphere_field_vec,
                                               fwd_sphere_field_grad,
                                               r0,NULL);
#endif
        if (!comp)
            goto bad;
        field       = FwdCompData::fwd_comp_field;
        vec_field   = FwdCompData::fwd_comp_field_vec;
        field_grad  = FwdCompData::fwd_comp_field_grad;
        client      = comp;
    }
    /*
       * Count the sources
       */
    for (k = 0, nsource = 0; k < nspace; k++)
        nsource += spaces[k]->nuse;
    /*
       * Allocate space for the solution
       */
    if (fixed_ori)
        res = ALLOC_CMATRIX_40(nsource,nmeg);
    else
        res = ALLOC_CMATRIX_40(3*nsource,nmeg);
    if (resp_grad) {
        if (fixed_ori)
            res_grad = ALLOC_CMATRIX_40(3*nsource,nmeg);
        else
            res_grad = ALLOC_CMATRIX_40(3*3*nsource,nmeg);
    }
    /*
    * Set up the argument for the field computation
    */
    one_arg = new FwdThreadArg();
    one_arg->res            = res;
    one_arg->res_grad       = res_grad;
    one_arg->off            = 0;
    one_arg->coils_els      = coils;
    one_arg->client         = client;
    one_arg->s              = NULL;
    one_arg->fixed_ori      = fixed_ori;
    one_arg->field_pot      = field;
    one_arg->vec_field_pot  = vec_field;
    one_arg->field_pot_grad = field_grad;

    if (nproc < 2)
        use_threads = false;

    if (use_threads) {
        int            nthread  = (fixed_ori || vec_field || nproc < 6) ? nspace : 3*nspace;
        QList <FwdThreadArg*> args; //fwdThreadArg   *args    = MALLOC_40(nthread,fwdThreadArg);
        int            stat;
        /*
        * We need copies to allocate separate workspace for each thread
        */
        if (fixed_ori || vec_field || nproc < 6) {
            for (k = 0, off = 0; k < nthread; k++) {
                FwdThreadArg* t_arg = FwdThreadArg::create_meg_multi_thread_duplicate(one_arg,bem_model != NULL);
                t_arg->s   = spaces[k];
                t_arg->off = off;
                off = fixed_ori ? off + spaces[k]->nuse : off + 3*spaces[k]->nuse;
                args.append(t_arg);
            }
            fprintf(stderr,"%d processors. I will use one thread for each of the %d source spaces.\n",
                    nproc,nspace);
        }
        else {
            for (k = 0, off = 0, q = 0; k < nspace; k++) {
                for (p = 0; p < 3; p++,q++) {
                    FwdThreadArg* t_arg = FwdThreadArg::create_meg_multi_thread_duplicate(one_arg,bem_model != NULL);
                    t_arg->s    = spaces[k];
                    t_arg->off  = off;
                    t_arg->comp = p;
                    args.append(t_arg);
                }
                off = fixed_ori ? off + spaces[k]->nuse : off + 3*spaces[k]->nuse;
            }
            fprintf(stderr,"%d processors. I will use %d threads : %d source spaces x 3 source components.\n",
                    nproc,nthread,nspace);
        }
        fprintf(stderr,"Computing MEG at %d source locations (%s orientations)...",
                nsource,fixed_ori ? "fixed" : "free");
        /*
        * Ready to start the threads & Wait for them to complete
        */
        QtConcurrent::blockingMap(args, meg_eeg_fwd_one_source_space);
        /*
        * Check the results
        */
        for (k = 0, stat = OK; k < nthread; k++)
            if (args[k]->stat != OK) {
                stat = FAIL;
                break;
            }
        for (k = 0; k < args.size(); k++)//nthread == args.size()
            FwdThreadArg::free_meg_multi_thread_duplicate(args[k],bem_model != NULL);
        if (stat != OK)
            goto bad;
    }
    else {
        fprintf(stderr,"Computing MEG at %d source locations (%s orientations, no threads)...",
                nsource,fixed_ori ? "fixed" : "free");
        for (k = 0, off = 0; k < nspace; k++) {
            one_arg->s   = spaces[k];
            one_arg->off = off;
            meg_eeg_fwd_one_source_space(one_arg);
            if (one_arg->stat != OK)
                goto bad;
            off = fixed_ori ? off + one_arg->s->nuse : off + 3*one_arg->s->nuse;
        }
    }
    fprintf(stderr,"done.\n");
    {
        QStringList orig_names;
        for (k = 0; k < nmeg; k++)
            orig_names.append(coils->coils[k]->chname);
        names = orig_names;
    }
    if(one_arg)
        delete one_arg;
    if(comp)
        delete comp;

    *resp = MneNamedMatrix::build_named_matrix(fixed_ori ? nsource : 3*nsource,
                                               nmeg,
                                               emptyList,
                                               names,
                                               res);
    if (resp_grad && res_grad)
        *resp_grad = MneNamedMatrix::build_named_matrix(fixed_ori ? 3*nsource : 3*3*nsource,
                                                        nmeg,
                                                        emptyList,
                                                        names,
                                                        res_grad);
    return OK;

bad : {
        if(one_arg)
            delete one_arg;
        if(comp)
            delete comp;
        FREE_CMATRIX_40(res);
        FREE_CMATRIX_40(res_grad);
        return FAIL;
    }
}

//*************************************************************************************************************

int FwdBemModel::compute_forward_eeg(MneSourceSpaceOld **spaces, int nspace, FwdCoilSet *els, bool fixed_ori, FwdBemModel *bem_model, FwdEegSphereModel *m, bool use_threads, MneNamedMatrix **resp, MneNamedMatrix **resp_grad)
/*
    * Compute the EEG forward solution
    * Use either the sphere model or BEM in the calculations
    */
{
    float            **res = NULL;          /* The forward solution matrix */
    float            **res_grad = NULL;     /* The gradient with respect to the dipole position */
    fwdFieldFunc     pot;                   /* Computes the potentials for one dipole orientation */
    fwdVecFieldFunc  vec_pot;               /* Computes the potentials for all dipole orientations */
    fwdFieldGradFunc pot_grad;              /* Computes the potential and gradient with respect to dipole position
                                             * for one dipole orientation */
    int             nsource;                /* Total number of sources */
    int             neeg = els->ncoil;      /* Number of channels */
    int             k,p,q,off;
    QStringList     names;                  /* Channel names */
    void            *client;
    FwdThreadArg*   one_arg = NULL;
    int             nproc = QThread::idealThreadCount();
    QStringList     emptyList;
    /*
       * Count the sources
       */
    for (k = 0, nsource = 0; k < nspace; k++)
        nsource += spaces[k]->nuse;

    if (bem_model) {
        if (fwd_bem_specify_els(bem_model,els) == FAIL)
            goto bad;
        client   = bem_model;
        pot      = fwd_bem_pot_els;
        vec_pot  = NULL;
#ifdef TEST
        fprintf(stderr,"Using differences.\n");
        pot_grad = my_bem_pot_grad;
#else
        pot_grad = fwd_bem_pot_grad_els;
#endif
    }
    else {
        if (m->nfit == 0) {
            fprintf(stderr,"Using the standard series expansion for a multilayer sphere model for EEG\n");
            pot      = FwdEegSphereModel::fwd_eeg_multi_spherepot_coil1;
            vec_pot  = NULL;
            pot_grad = NULL;
        }
        else {
            fprintf(stderr,"Using the equivalent source approach in the homogeneous sphere for EEG\n");
            pot      = FwdEegSphereModel::fwd_eeg_spherepot_coil;
            vec_pot  = FwdEegSphereModel::fwd_eeg_spherepot_coil_vec;
            pot_grad = FwdEegSphereModel::fwd_eeg_spherepot_grad_coil;
        }
        client   = m;
    }
    /*
    * Allocate space for the solution
    */
    if (fixed_ori)
        res = ALLOC_CMATRIX_40(nsource,neeg);
    else
        res = ALLOC_CMATRIX_40(3*nsource,neeg);
    if (resp_grad) {
        if (!pot_grad) {
            qCritical("EEG gradient calculation function not available");
            goto bad;
        }
        if (fixed_ori)
            res_grad = ALLOC_CMATRIX_40(3*nsource,neeg);
        else
            res_grad = ALLOC_CMATRIX_40(3*3*nsource,neeg);
    }
    /*
       * Set up the argument for the field computation
       */
    one_arg = new FwdThreadArg();
    one_arg->res            = res;
    one_arg->res_grad       = res_grad;
    one_arg->off            = 0;
    one_arg->coils_els      = els;
    one_arg->client         = client;
    one_arg->s              = NULL;
    one_arg->fixed_ori      = fixed_ori;
    one_arg->field_pot      = pot;
    one_arg->vec_field_pot  = vec_pot;
    one_arg->field_pot_grad = pot_grad;

    if (nproc < 2)
        use_threads = false;

    if (use_threads) {
        int            nthread  = (fixed_ori || vec_pot || nproc < 6) ? nspace : 3*nspace;
        QList <FwdThreadArg*> args; //FwdThreadArg*   *args    = MALLOC_40(nthread,FwdThreadArg*);
        int            stat;
        /*
        * We need copies to allocate separate workspace for each thread
        */
        if (fixed_ori || vec_pot || nproc < 6) {
            for (k = 0, off = 0; k < nthread; k++) {
                FwdThreadArg* t_arg = FwdThreadArg::create_eeg_multi_thread_duplicate(one_arg,bem_model != NULL);
                t_arg->s   = spaces[k];
                t_arg->off = off;
                off = fixed_ori ? off + spaces[k]->nuse : off + 3*spaces[k]->nuse;
                args.append(t_arg);
            }
            printf("%d processors. I will use one thread for each of the %d source spaces.\n",nproc,nspace);
        }
        else {
            for (k = 0, off = 0, q = 0; k < nspace; k++) {
                for (p = 0; p < 3; p++,q++) {
                    FwdThreadArg* t_arg = FwdThreadArg::create_eeg_multi_thread_duplicate(one_arg,bem_model != NULL);
                    t_arg->s    = spaces[k];
                    t_arg->off  = off;
                    t_arg->comp = p;
                    args.append(t_arg);
                }
                off = fixed_ori ? off + spaces[k]->nuse : off + 3*spaces[k]->nuse;
            }
            printf("%d processors. I will use %d threads : %d source spaces x 3 source components.\n",nproc,nthread,nspace);
        }
        printf("Computing EEG at %d source locations (%s orientations)...",
                nsource,fixed_ori ? "fixed" : "free");
        /*
        * Ready to start the threads & Wait for them to complete
        */
        QtConcurrent::blockingMap(args, meg_eeg_fwd_one_source_space);
        /*
        * Check the results
        */
        for (k = 0, stat = OK; k < nthread; k++)
            if (args[k]->stat != OK) {
                stat = FAIL;
                break;
            }
        for (k = 0; k < args.size(); k++)//nthread == args.size()
            FwdThreadArg::free_eeg_multi_thread_duplicate(args[k],bem_model != NULL);
        if (stat != OK)
            goto bad;
    }
    else {
        fprintf(stderr,"Computing EEG at %d source locations (%s orientations, no threads)...",
                nsource,fixed_ori ? "fixed" : "free");
        for (k = 0, off = 0; k < nspace; k++) {
            one_arg->s   = spaces[k];
            one_arg->off = off;
            meg_eeg_fwd_one_source_space(one_arg);
            if (one_arg->stat != OK)
                goto bad;
            off = fixed_ori ? off + one_arg->s->nuse : off + 3*one_arg->s->nuse;
        }
    }
    fprintf(stderr,"done.\n");
    {
        QStringList orig_names;
        for (k = 0; k < neeg; k++)
            orig_names.append(els->coils[k]->chname);
        names = orig_names;
    }
    if(one_arg)
        delete one_arg;
    *resp = MneNamedMatrix::build_named_matrix(fixed_ori ? nsource : 3*nsource,neeg,emptyList,names,res);
    if (resp_grad && res_grad)
        *resp_grad = MneNamedMatrix::build_named_matrix(fixed_ori ? 3*nsource : 3*3*nsource,neeg,emptyList,
                                            names,res_grad);
    return OK;

bad : {
        if(one_arg)
            delete one_arg;
        FREE_CMATRIX_40(res);
        FREE_CMATRIX_40(res_grad);
        return FAIL;
    }
}

//*************************************************************************************************************

#define EPS   1e-5   /* Points closer to origin than this many
                        meters are considered to be at the
                        origin */
#define CEPS       1e-5

int FwdBemModel::fwd_sphere_field(float *rd, float Q[], FwdCoilSet *coils, float Bval[], void *client)	/* Client data will be the sphere model origin */
{
    /* This version uses Jukka Sarvas' field computation
         for details, see

         Jukka Sarvas:

         Basic mathematical and electromagnetic concepts
         of the biomagnetic inverse problem,

         Phys. Med. Biol. 1987, Vol. 32, 1, 11-22

         The formulas have been manipulated for efficient computation
         by Matti Hamalainen, February 1990

      */
    float *r0 = (float *)client;      /* The sphere model origin */
    float v[3],a_vec[3];
    float a,a2,r,r2;
    float ar,ar0,rr0;
    float vr,ve,re,r0e;
    float F,g0,gr,result,sum;
    int   j,k,p;
    FwdCoil* this_coil;
    float *this_pos,*this_dir;	/* These point to the coil structure! */
    int   np;
    float myrd[3];
    float pos[3];
    /*
       * Shift to the sphere model coordinates
       */
    for (p = 0; p < 3; p++)
        myrd[p] = rd[p] - r0[p];
    rd = myrd;
    /*
       * Check for a dipole at the origin
       */
    for (k = 0 ; k < coils->ncoil ; k++)
        if (FWD_IS_MEG_COIL(coils->coils[k]->coil_class))
            Bval[k] = 0.0;
    r = VEC_LEN_40(rd);
    if (r > EPS)	{		/* The hard job */

        CROSS_PRODUCT_40(Q,rd,v);

        for (k = 0; k < coils->ncoil; k++) {
            this_coil = coils->coils[k];
            if (FWD_IS_MEG_COIL(this_coil->type)) {

                np = this_coil->np;

                for (j = 0, sum = 0.0; j < np; j++) {

                    this_pos = this_coil->rmag[j];
                    this_dir = this_coil->cosmag[j];

                    for (p = 0; p < 3; p++)
                        pos[p] = this_pos[p] - r0[p];
                    this_pos = pos;
                    result = 0.0;

                    /* Vector from dipole to the field point */

                    VEC_DIFF_40(rd,this_pos,a_vec);

                    /* Compute the dot products needed */

                    a2  = VEC_DOT_40(a_vec,a_vec);       a = sqrt(a2);

                    if (a > 0.0) {
                        r2  = VEC_DOT_40(this_pos,this_pos); r = sqrt(r2);
                        if (r > 0.0) {
                            rr0 = VEC_DOT_40(this_pos,rd);
                            ar = (r2-rr0);
                            if (std::fabs(ar/(a*r)+1.0) > CEPS) { /* There is a problem on the negative 'z' axis if the dipole location
                                                    * and the field point are on the same line */
                                ar0  = ar/a;

                                ve = VEC_DOT_40(v,this_dir); vr = VEC_DOT_40(v,this_pos);
                                re = VEC_DOT_40(this_pos,this_dir); r0e = VEC_DOT_40(rd,this_dir);

                                /* The main ingredients */

                                F  = a*(r*a + ar);
                                gr = a2/r + ar0 + 2.0*(a+r);
                                g0 = a + 2*r + ar0;

                                /* Mix them together... */

                                sum = sum + this_coil->w[j]*(ve*F + vr*(g0*r0e - gr*re))/(F*F);
                            }
                        }
                    }
                }				/* All points done */
                Bval[k] = MAG_FACTOR*sum;
            }
        }
    }
    return OK;          /* Happy conclusion: this works always */
}

//*************************************************************************************************************

int FwdBemModel::fwd_sphere_field_vec(float *rd, FwdCoilSet *coils, float **Bval, void *client)	/* Client data will be the sphere model origin */
{
    /* This version uses Jukka Sarvas' field computation
         for details, see

         Jukka Sarvas:

         Basic mathematical and electromagnetic concepts
         of the biomagnetic inverse problem,

         Phys. Med. Biol. 1987, Vol. 32, 1, 11-22

         The formulas have been manipulated for efficient computation
         by Matti Hamalainen, February 1990

         The idea of matrix kernels is from

         Mosher, Leahy, and Lewis: EEG and MEG: Forward Solutions for Inverse Methods

         which has been simplified here using standard vector notation

      */
    float *r0 = (float *)client;      /* The sphere model origin */
    float a_vec[3],v1[3],v2[3];
    float a,a2,r,r2;
    float ar,ar0,rr0;
    float re,r0e;
    float F,g0,gr,g,sum[3];
    int   j,k,p;
    FwdCoil* this_coil;
    float *this_pos,*this_dir;	/* These point to the coil structure! */
    int   np;
    float myrd[3];
    float pos[3];
    /*
       * Shift to the sphere model coordinates
       */
    for (p = 0; p < 3; p++)
        myrd[p] = rd[p] - r0[p];
    rd = myrd;
    /*
       * Check for a dipole at the origin
       */
    r = VEC_LEN_40(rd);
    for (k = 0; k < coils->ncoil; k++) {
        this_coil = coils->coils[k];
        if (FWD_IS_MEG_COIL(this_coil->coil_class)) {
            if (r < EPS) {
                Bval[0][k] = Bval[1][k] = Bval[2][k] = 0.0;
            }
            else { 	/* The hard job */

                np = this_coil->np;
                sum[0] = sum[1] = sum[2] = 0.0;

                for (j = 0; j < np; j++) {

                    this_pos = this_coil->rmag[j];
                    this_dir = this_coil->cosmag[j];

                    for (p = 0; p < 3; p++)
                        pos[p] = this_pos[p] - r0[p];
                    this_pos = pos;

                    /* Vector from dipole to the field point */

                    VEC_DIFF_40(rd,this_pos,a_vec);

                    /* Compute the dot products needed */

                    a2  = VEC_DOT_40(a_vec,a_vec);       a = sqrt(a2);

                    if (a > 0.0) {
                        r2  = VEC_DOT_40(this_pos,this_pos); r = sqrt(r2);
                        if (r > 0.0) {
                            rr0 = VEC_DOT_40(this_pos,rd);
                            ar = (r2-rr0);
                            if (std::fabs(ar/(a*r)+1.0) > CEPS) { /* There is a problem on the negative 'z' axis if the dipole location
                                                    * and the field point are on the same line */

                                /* The main ingredients */

                                ar0  = ar/a;
                                F  = a*(r*a + ar);
                                gr = a2/r + ar0 + 2.0*(a+r);
                                g0 = a + 2*r + ar0;

                                re = VEC_DOT_40(this_pos,this_dir); r0e = VEC_DOT_40(rd,this_dir);
                                CROSS_PRODUCT_40(rd,this_dir,v1);
                                CROSS_PRODUCT_40(rd,this_pos,v2);

                                g = (g0*r0e - gr*re)/(F*F);
                                /*
                     * Mix them together...
                     */
                                for (p = 0; p < 3; p++)
                                    sum[p] = sum[p] + this_coil->w[j]*(v1[p]/F + v2[p]*g);
                            }
                        }
                    }
                }				/* All points done */
                for (p = 0; p < 3; p++)
                    Bval[p][k] = MAG_FACTOR*sum[p];
            }
        }
    }
    return OK;			/* Happy conclusion: this works always */
}

//*************************************************************************************************************

int FwdBemModel::fwd_sphere_field_grad(float *rd, float Q[], FwdCoilSet *coils, float Bval[], float xgrad[], float ygrad[], float zgrad[], void *client)  /* Client data to be passed to some foward modelling routines */
/*
* Compute the derivatives of the sphere model field with respect to
* dipole coordinates
*/
{
    /* This version uses Jukka Sarvas' field computation
         for details, see

         Jukka Sarvas:

         Basic mathematical and electromagnetic concepts
         of the biomagnetic inverse problem,

         Phys. Med. Biol. 1987, Vol. 32, 1, 11-22

         The formulas have been manipulated for efficient computation
         by Matti Hamalainen, February 1990

         */

    float v[3],a_vec[3];
    float a,a2,r,r2;
    float ar,rr0;
    float vr,ve,re,r0e;
    float F,g0,gr,result,G,F2;

    int   j,k,p;
    float huu;
    float ggr[3],gg0[3];		/* Gradient of gr & g0 */
    float ga[3];			/* Grapdient of a */
    float gar[3];			/* Gradient of ar */
    float gFF[3];			/* Gradient of F divided by F */
    float gresult[3];
    float eQ[3],rQ[3];		/* e x Q and r x Q */
    int   do_field = 0;
    FwdCoil* this_coil;
    float *this_pos,*this_dir;
    int   np;
    float myrd[3];
    float pos[3];
    float *r0 = (float *)client;      /* The sphere model origin */
    /*
       * Shift to the sphere model coordinates
       */
    for (p = 0; p < 3; p++)
        myrd[p] = rd[p] - r0[p];
    rd = myrd;

    if (Bval)
        do_field = 1;

    /* Check for a dipole at the origin */

    r = VEC_LEN_40(rd);
    for (k = 0; k < coils->ncoil ; k++) {
        if (FWD_IS_MEG_COIL(coils->coils[k]->coil_class)) {
            if (do_field)
                Bval[k] = 0.0;
            xgrad[k] = 0.0;
            ygrad[k] = 0.0;
            zgrad[k] = 0.0;
        }
    }
    if (r > EPS) {		/* The hard job */

        v[X_40] = Q[Y_40]*rd[Z_40] - Q[Z_40]*rd[Y_40];
        v[Y_40] = -Q[X_40]*rd[Z_40] + Q[Z_40]*rd[X_40];
        v[Z_40] = Q[X_40]*rd[Y_40] - Q[Y_40]*rd[X_40];

        for (k = 0 ; k < coils->ncoil ; k++) {

            this_coil = coils->coils[k];

            if (FWD_IS_MEG_COIL(this_coil->type)) {

                np = this_coil->np;

                for (j = 0; j < np; j++) {

                    this_pos = this_coil->rmag[j];
                    /*
           * Shift to the sphere model coordinates
           */
                    for (p = 0; p < 3; p++)
                        pos[p] = this_pos[p] - r0[p];
                    this_pos = pos;

                    this_dir = this_coil->cosmag[j];

                    /* Vector from dipole to the field point */

                    a_vec[X_40] = this_pos[X_40] - rd[X_40];
                    a_vec[Y_40] = this_pos[Y_40] - rd[Y_40];
                    a_vec[Z_40] = this_pos[Z_40] - rd[Z_40];

                    /* Compute the dot and cross products needed */

                    a2  = VEC_DOT_40(a_vec,a_vec);       a = sqrt(a2);
                    r2  = VEC_DOT_40(this_pos,this_pos); r = sqrt(r2);
                    rr0 = VEC_DOT_40(this_pos,rd);
                    ar  = (r2 - rr0)/a;

                    ve = VEC_DOT_40(v,this_dir); vr = VEC_DOT_40(v,this_pos);
                    re = VEC_DOT_40(this_pos,this_dir); r0e = VEC_DOT_40(rd,this_dir);

                    /* eQ = this_dir x Q */

                    eQ[X_40] = this_dir[Y_40]*Q[Z_40] - this_dir[Z_40]*Q[Y_40];
                    eQ[Y_40] = -this_dir[X_40]*Q[Z_40] + this_dir[Z_40]*Q[X_40];
                    eQ[Z_40] = this_dir[X_40]*Q[Y_40] - this_dir[Y_40]*Q[X_40];

                    /* rQ = this_pos x Q */

                    rQ[X_40] = this_pos[Y_40]*Q[Z_40] - this_pos[Z_40]*Q[Y_40];
                    rQ[Y_40] = -this_pos[X_40]*Q[Z_40] + this_pos[Z_40]*Q[X_40];
                    rQ[Z_40] = this_pos[X_40]*Q[Y_40] - this_pos[Y_40]*Q[X_40];

                    /* The main ingredients */

                    F  = a*(r*a + r2 - rr0);
                    F2 = F*F;
                    gr = a2/r + ar + 2.0*(a+r);
                    g0 = a + 2.0*r + ar;
                    G = g0*r0e - gr*re;

                    /* Mix them together... */

                    result = (ve*F + vr*G)/F2;

                    /* The computation of the gradient... */

                    huu = 2.0 + 2.0*a/r;
                    for (p = X_40; p <= Z_40; p++) {
                        ga[p] = -a_vec[p]/a;
                        gar[p] = -(ga[p]*ar + this_pos[p])/a;
                        gg0[p] = ga[p] + gar[p];
                        ggr[p] = huu*ga[p] + gar[p];
                        gFF[p] = ga[p]/a - (r*a_vec[p] + a*this_pos[p])/F;
                        gresult[p] = -2.0*result*gFF[p] + (eQ[p]+gFF[p]*ve)/F +
                                (rQ[p]*G + vr*(gg0[p]*r0e + g0*this_dir[p] - ggr[p]*re))/F2;
                    }

                    if (do_field)
                        Bval[k] = Bval[k] + this_coil->w[j]*result;
                    xgrad[k] = xgrad[k] + this_coil->w[j]*gresult[X_40];
                    ygrad[k] = ygrad[k] + this_coil->w[j]*gresult[Y_40];
                    zgrad[k] = zgrad[k] + this_coil->w[j]*gresult[Z_40];
                }
                if (do_field)
                    Bval[k] = MAG_FACTOR*Bval[k];
                xgrad[k] = MAG_FACTOR*xgrad[k];
                ygrad[k] = MAG_FACTOR*ygrad[k];
                zgrad[k] = MAG_FACTOR*zgrad[k];
            }
        }
    }
    return OK;			/* Happy conclusion: this works always */
}

//*************************************************************************************************************

int FwdBemModel::fwd_mag_dipole_field(float *rm, float M[], FwdCoilSet *coils, float Bval[], void *client)	/* Client data will be the sphere model origin */
/*
* This is for a specific dipole component
*/
{
    int     j,k,np;
    FwdCoil* this_coil;
    float   sum,diff[3],dist,dist2,dist5,*dir;

    for (k = 0; k < coils->ncoil; k++) {
        this_coil = coils->coils[k];
        if (FWD_IS_MEG_COIL(this_coil->type)) {
            np = this_coil->np;
            /*
           * Go through all points
           */
            for (j = 0, sum = 0.0; j < np; j++) {
                dir = this_coil->cosmag[j];
                VEC_DIFF_40(rm,this_coil->rmag[j],diff);
                dist = VEC_LEN_40(diff);
                if (dist > EPS) {
                    dist2 = dist*dist;
                    dist5 = dist2*dist2*dist;
                    sum = sum + this_coil->w[j]*(3*VEC_DOT_40(M,diff)*VEC_DOT_40(diff,dir) - dist2*VEC_DOT_40(M,dir))/dist5;
                }
            }				/* All points done */
            Bval[k] = MAG_FACTOR*sum;
        }
        else if (this_coil->type == FWD_COILC_EEG)
            Bval[k] = 0.0;
    }
    return OK;
}

//*************************************************************************************************************

int FwdBemModel::fwd_mag_dipole_field_vec(float *rm, FwdCoilSet *coils, float **Bval, void *client)     /* Client data will be the sphere model origin */
/*
* This is for all dipole components
* For EEG this produces a zero result
*/
{
    int     j,k,p,np;
    FwdCoil* this_coil;
    float   sum[3],diff[3],dist,dist2,dist5,*dir;

    for (k = 0; k < coils->ncoil; k++) {
        this_coil = coils->coils[k];
        if (FWD_IS_MEG_COIL(this_coil->type)) {
            np = this_coil->np;
            sum[0] = sum[1] = sum[2] = 0.0;
            /*
           * Go through all points
           */
            for (j = 0; j < np; j++) {
                dir = this_coil->cosmag[j];
                VEC_DIFF_40(rm,this_coil->rmag[j],diff);
                dist = VEC_LEN_40(diff);
                if (dist > EPS) {
                    dist2 = dist*dist;
                    dist5 = dist2*dist2*dist;
                    for (p = 0; p < 3; p++)
                        sum[p] = sum[p] + this_coil->w[j]*(3*diff[p]*VEC_DOT_40(diff,dir) - dist2*dir[p])/dist5;
                }
            }           /* All points done */
            for (p = 0; p < 3; p++)
                Bval[p][k] = MAG_FACTOR*sum[p];
        }
        else if (this_coil->type == FWD_COILC_EEG) {
            for (p = 0; p < 3; p++)
                Bval[p][k] = 0.0;
        }
    }
    return OK;
}