void write_faces(std::ofstream& fout,
const VectorI& faces,
const size_t vertex_per_face,
const VectorI& uv_indices=VectorI::Zero(0)) {
if (vertex_per_face != 3 && vertex_per_face != 4) {
std::stringstream err_msg;
err_msg << "OBJ format does not support non-triangle non-quad face with "
<< vertex_per_face << " vertices." << std::endl;
throw RuntimeError(err_msg.str());
}
const size_t num_faces = faces.size() / vertex_per_face;
const size_t num_uvs = uv_indices.size() / 2;
if (num_uvs == 0) {
for (size_t i=0; i<num_faces; i++) {
const auto& f = faces.segment(i*vertex_per_face, vertex_per_face);
fout << "f";
for (size_t j=0; j<vertex_per_face; j++) {
fout << " " << f[j] + 1;
}
fout << std::endl;
}
} else {
for (size_t i=0; i<num_faces; i++) {
const auto& f = faces.segment(i*vertex_per_face, vertex_per_face);
const auto& uv = uv_indices.segment(i*vertex_per_face, vertex_per_face);
fout << "f ";
for (size_t j=0; j<vertex_per_face; j++) {
fout << f[j] + 1 << "/" << uv[j] + 1 << " ";
}
fout << std::endl;
}
}
}
void correct_tet_orientation(const VectorF& vertices, VectorI& voxels) {
const size_t num_voxels = voxels.size() / 4;
for (size_t i=0; i<num_voxels; i++) {
const VectorI tet = voxels.segment(i*4, 4);
const Vector3F& v1 = vertices.segment(tet[0]*3, 3);
const Vector3F& v2 = vertices.segment(tet[1]*3, 3);
const Vector3F& v3 = vertices.segment(tet[2]*3, 3);
const Vector3F& v4 = vertices.segment(tet[3]*3, 3);
if (!positive_orientated(v1, v2, v3, v4)) {
voxels[i*4] = tet[1];
voxels[i*4+1] = tet[0];
}
}
}