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Do not raise an error for flipped triangles if their area contribution is negligible.

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PiperOrigin-RevId: 474552367
Change-Id: I9727a74e50a9bab9b04bb0de0b64e11587ed36f1
This commit is contained in:
Alessio Quaglino
2022-09-15 07:06:22 -07:00
committed by Copybara-Service
parent c8517e63a4
commit 0e05e7ce52
2 changed files with 103 additions and 55 deletions
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src/user/user_mesh.cc
+81 -55
View File
@@ -48,6 +48,38 @@ extern "C" {
using std::string;
using std::vector;
// compute triangle area, surface normal, center
static mjtNum _triangle(mjtNum* normal, mjtNum* center,
const float* v1, const float* v2, const float* v3) {
// center
if (center) {
for (int i=0; i<3; i++) {
center[i] = (v1[i] + v2[i] + v3[i])/3;
}
}
// normal = (v2-v1) cross (v3-v1)
double b[3] = { v2[0]-v1[0], v2[1]-v1[1], v2[2]-v1[2] };
double c[3] = { v3[0]-v1[0], v3[1]-v1[1], v3[2]-v1[2] };
mju_cross(normal, b, c);
// get length
double len = mju_norm3(normal);
// ignore small faces
if (len<mjMINVAL) {
return 0;
}
// normalize
normal[0] /= len;
normal[1] /= len;
normal[2] /= len;
// return area
return len/2;
}
//------------------ class mjCMesh implementation --------------------------------------------------
// constructor
@@ -212,15 +244,27 @@ void mjCMesh::Compile(const mjVFS* vfs) {
face = (int*) mju_malloc(3*nface*sizeof(int));
memcpy(face, userface.data(), 3*nface*sizeof(int));
// check vertices exist
for (auto vertex_index : userface) {
if (vertex_index>=nvert || vertex_index < 0) {
throw mjCError(this, "found index in userface that exceeds uservert size.");
}
}
// create half-edge structure (if mesh was in XML)
if (useredge.empty()) {
for (int i=0; i<nface; i++) {
int v0 = userface[3*i+0];
int v1 = userface[3*i+1];
int v2 = userface[3*i+2];
useredge.push_back(std::pair(v0, v1));
useredge.push_back(std::pair(v1, v2));
useredge.push_back(std::pair(v2, v0));
mjtNum normal[3];
if (_triangle(normal, nullptr, vert+3*v0, vert+3*v1, vert+3*v2)>sqrt(mjMINVAL)) {
useredge.push_back(std::pair(v0, v1));
useredge.push_back(std::pair(v1, v2));
useredge.push_back(std::pair(v2, v0));
} else {
mju_warning("Degenerate triangle found, its orientation will not be checked.");
}
}
}
}
@@ -554,6 +598,7 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
bool has_normals = !attrib.normals.empty();
bool has_texcoords = !attrib.texcoords.empty();
bool righthand = (scale[0]*scale[1]*scale[2] > 0);
// iterate over mesh faces
int index_in_mesh_indices = 0;
for (int face = 0; face < mesh.num_face_vertices.size(); face++) {
@@ -562,6 +607,7 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
this, "only tri or quad meshes are supported for OBJ (file '%s')",
filename.c_str());
}
// add face
std::vector<std::array<tinyobj::index_t, 3>> faces;
tinyobj::index_t v0 = mesh.indices[index_in_mesh_indices];
@@ -569,18 +615,12 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
tinyobj::index_t v2 = mesh.indices[index_in_mesh_indices+2];
std::array<tinyobj::index_t, 3> face1 = {v0, v1, v2};
faces.push_back(face1);
// add edges
useredge.push_back(std::pair(v0.vertex_index, v1.vertex_index));
useredge.push_back(std::pair(v1.vertex_index, v2.vertex_index));
useredge.push_back(std::pair(v2.vertex_index, v0.vertex_index));
// handle quad: add second triangle with 4th vertex
if (mesh.num_face_vertices[face] == 4) {
tinyobj::index_t v3 = mesh.indices[index_in_mesh_indices+3];
std::array<tinyobj::index_t, 3> face2 = {v0, v2, v3};
faces.push_back(face2);
useredge.push_back(std::pair(v0.vertex_index, v2.vertex_index));
useredge.push_back(std::pair(v2.vertex_index, v3.vertex_index));
useredge.push_back(std::pair(v3.vertex_index, v0.vertex_index));
}
for (const auto& face_indices : faces) {
int index_of_first_vertex = uservert.size()/3;
@@ -590,6 +630,7 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
uservert.end(),
attrib.vertices.begin() + 3*tinyobj_index.vertex_index,
attrib.vertices.begin() + 3*tinyobj_index.vertex_index + 3);
// for each vertex, add its normal
if (has_normals) {
usernormal.insert(
@@ -597,6 +638,7 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
attrib.normals.begin() + 3*tinyobj_index.normal_index,
attrib.normals.begin() + 3*tinyobj_index.normal_index + 3);
}
// for each vertex, add two entries to usertexcoord
if (has_texcoords) {
usertexcoord.push_back(
@@ -605,14 +647,33 @@ void mjCMesh::LoadOBJ(const mjVFS* vfs) {
1-attrib.texcoords[2*tinyobj_index.texcoord_index + 1]);
}
}
// add vertex indices (in uservert) to userface
userface.push_back(index_of_first_vertex);
if (righthand) {
userface.push_back(index_of_first_vertex+1);
userface.push_back(index_of_first_vertex+2);
int i0 = index_of_first_vertex;
int i1 = index_of_first_vertex+1;
int i2 = index_of_first_vertex+2;
// add edges
const float *v0 = uservert.data() + 3*i0;
const float *v1 = uservert.data() + 3*i1;
const float *v2 = uservert.data() + 3*i2;
mjtNum normal[3];
// only consider edges if the face contribution is significant
if (_triangle(normal, nullptr, v0, v1, v2)>sqrt(mjMINVAL)) {
useredge.push_back(std::pair(face_indices[0].vertex_index, face_indices[1].vertex_index));
useredge.push_back(std::pair(face_indices[1].vertex_index, face_indices[2].vertex_index));
useredge.push_back(std::pair(face_indices[2].vertex_index, face_indices[0].vertex_index));
} else {
userface.push_back(index_of_first_vertex+2);
userface.push_back(index_of_first_vertex+1);
mju_warning("Degenerate triangle found, its orientation will not be checked.");
}
// add vertex indices (in uservert) to userface
userface.push_back(i0);
if (righthand) {
userface.push_back(i1);
userface.push_back(i2);
} else {
userface.push_back(i2);
userface.push_back(i1);
}
}
index_in_mesh_indices += mesh.num_face_vertices[face];
@@ -859,41 +920,6 @@ void mjCMesh::LoadMSH(const mjVFS* vfs) {
// compute triangle area, surface normal, center
static double _areaNrmCen(double* normal, double* center,
const float* v1, const float* v2, const float* v3) {
// center
if (center) {
for (int i=0; i<3; i++) {
center[i] = (v1[i] + v2[i] + v3[i])/3;
}
}
// normal = (v2-v1) cross (v3-v1)
double b[3] = { v2[0]-v1[0], v2[1]-v1[1], v2[2]-v1[2] };
double c[3] = { v3[0]-v1[0], v3[1]-v1[1], v3[2]-v1[2] };
normal[0] = b[1]*c[2] - b[2]*c[1];
normal[1] = b[2]*c[0] - b[0]*c[2];
normal[2] = b[0]*c[1] - b[1]*c[0];
// get length
double len = sqrt(normal[0]*normal[0] + normal[1]*normal[1] + normal[2]*normal[2]);
// ignore small faces
if (len<mjMINVAL) {
return 0;
}
// normalize
normal[0] /= len;
normal[1] /= len;
normal[2] /= len;
// return area
return len/2;
}
// apply transformations
void mjCMesh::Process() {
for ( const auto type : { mjtMeshType::mjVOLUME_MESH, mjtMeshType::mjSHELL_MESH } ) {
@@ -992,7 +1018,7 @@ void mjCMesh::Process() {
}
// get area and center
double a = _areaNrmCen(nrm, cen, vert+3*face[3*i], vert+3*face[3*i+1], vert+3*face[3*i+2]);
double a = _triangle(nrm, cen, vert+3*face[3*i], vert+3*face[3*i+1], vert+3*face[3*i+2]);
// accumulate
for (j=0; j<3; j++) {
@@ -1017,7 +1043,7 @@ void mjCMesh::Process() {
GetVolumeRef(type) = 0;
for (i=0; i<nface; i++) {
// get area, normal and center
double a = _areaNrmCen(nrm, cen, vert+3*face[3*i], vert+3*face[3*i+1], vert+3*face[3*i+2]);
double a = _triangle(nrm, cen, vert+3*face[3*i], vert+3*face[3*i+1], vert+3*face[3*i+2]);
// compute and add volume
const double vec[3] = {cen[0]-facecen[0], cen[1]-facecen[1], cen[2]-facecen[2]};
@@ -1066,7 +1092,7 @@ void mjCMesh::Process() {
float* F = vert+3*face[3*i+2];
// get area, normal and center; update volume
double a = _areaNrmCen(nrm, cen, D, E, F);
double a = _triangle(nrm, cen, D, E, F);
double vol = type==mjSHELL_MESH ? a : mjuu_dot3(cen, nrm) * a / 3;
// if legacy computation requested, then always positive
test/user/user_mesh_test.cc
+22
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@@ -288,6 +288,28 @@ TEST_F(MujocoTest, FlippedFaceAllowedInertial) {
mj_deleteModel(model);
}
TEST_F(MujocoTest, FlippedFaceAllowedNegligibleArea) {
static constexpr char xml[] = R"(
<mujoco>
<asset>
<mesh name="example_mesh"
vertex="0 0 0 1 0 0 0 1 0 0 0 1 0 0 1"
face="2 0 3 0 1 3 1 2 3 0 2 1 0 3 4" />
</asset>
<worldbody>
<body>
<geom type="mesh" mesh="example_mesh"/>
</body>
</worldbody>
</mujoco>
)";
std::array<char, 1024> error;
mjModel* model = LoadModelFromString(xml, error.data(), error.size());
EXPECT_THAT(model, testing::NotNull());
CheckTetrahedronWasRescaled(model);
mj_deleteModel(model);
}
TEST_F(MujocoTest, AreaTooSmall) {
static constexpr char xml[] = R"(
<mujoco>