DensityGrid get_rasterized_fast(const Gaussian3Ds &gmm, const Floats &weights,
double cell_width, const BoundingBox3D &bb, double factor) {
DensityGrid ret(cell_width, bb, 0);
for (unsigned int ng = 0; ng < gmm.size(); ng++) {
Eigen::Matrix3d covar = get_covariance(gmm[ng]);
Eigen::Matrix3d inverse = Eigen::Matrix3d::Zero(3, 3);
double determinant;
bool invertible;
covar.computeInverseAndDetWithCheck(inverse, determinant, invertible);
IMP_INTERNAL_CHECK((invertible && determinant > 0),
"Tried to invert Gaussian, but it's not proper matrix");
double pre(get_gaussian_eval_prefactor(determinant));
Eigen::Vector3d evals = covar.eigenvalues().real();
double maxeval = sqrt(evals.maxCoeff());
double cutoff = factor * maxeval;
double cutoff2 = cutoff * cutoff;
Vector3D c = gmm[ng].get_center();
Vector3D lower = c - Vector3D(cutoff, cutoff, cutoff);
Vector3D upper = c + Vector3D(cutoff, cutoff, cutoff);
GridIndex3D lowerindex = ret.get_nearest_index(lower);
GridIndex3D upperindex = ret.get_nearest_index(upper);
Eigen::Vector3d center(c.get_data());
IMP_INTERNAL_CHECK(invertible, "matrix wasn't invertible! uh oh!");
IMP_GRID3D_FOREACH_SMALLER_EXTENDED_INDEX_RANGE(ret, upperindex, lowerindex,
upperindex, {
GridIndex3D i(voxel_index[0], voxel_index[1], voxel_index[2]);
Eigen::Vector3d r(get_vec_from_center(i, ret, center));
if (r.squaredNorm() < cutoff2) {
update_value(&ret, i, r, inverse, pre, weights[ng]);
}
})
}
return ret;
}
