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// Copyright Matt Overby 2020.
// Distributed under the MIT License.
#include "admmpd_tetmesh.h"
#include "admmpd_math.h"
#include <unordered_map>
#include <set>
#include "BLI_assert.h"
namespace admmpd {
using namespace Eigen;
void TetMesh::compute_masses(
TetMeshData *mesh,
const Eigen::MatrixXd *x,
Eigen::VectorXd *masses,
double density_kgm3)
{
BLI_assert(mesh != NULL);
BLI_assert(x != NULL);
BLI_assert(masses != NULL);
BLI_assert(density_kgm3 > 0);
// Source: https://github.com/mattoverby/mclscene/blob/master/include/MCL/TetMesh.hpp
// Computes volume-weighted masses for each vertex
// density_kgm3 is the unit-volume density
int nx = x->rows();
masses->resize(nx);
masses->setZero();
int n_tets = mesh->tets.rows();
for (int t=0; t<n_tets; ++t)
{
RowVector4i tet = mesh->tets.row(t);
RowVector3d tet_v0 = x->row(tet[0]);
Matrix3d edges;
edges.col(0) = x->row(tet[1]) - tet_v0;
edges.col(1) = x->row(tet[2]) - tet_v0;
edges.col(2) = x->row(tet[3]) - tet_v0;
double vol = std::abs((edges).determinant()/6.f);
double tet_mass = density_kgm3 * vol;
masses->operator[](tet[0]) += tet_mass / 4.f;
masses->operator[](tet[1]) += tet_mass / 4.f;
masses->operator[](tet[2]) += tet_mass / 4.f;
masses->operator[](tet[3]) += tet_mass / 4.f;
}
// Verify masses
for (int i=0; i<nx; ++i)
{
if (masses->operator[](i) <= 0.0)
{
printf("**TetMesh::compute_masses Error: unreferenced vertex\n");
masses->operator[](i)=1;
}
}
} // end compute masses
} // namespace admmpd
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