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Add RemoveDuplicatedTriangles feature using tensor API #6409

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Add RemoveDuplicatedTriangles feature using tensor API #6409

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98fe062
Add RemoveDuplicatedTriangles feature using tensor API
PierreIntel Oct 5, 2023
9c53c9d
Add C++ and python documentation
PierreIntel Oct 5, 2023
a6ed51c
Change check of numbers of triangles to 2 and return if the number of…
PierreIntel Oct 12, 2023
3aa93dd
Use the SelectFacesByMask() function to remove duplicates triangles w…
PierreIntel Oct 12, 2023
c890dc8
use the operator[] and sort instead of multiples if
PierreIntel Oct 25, 2023
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75 changes: 75 additions & 0 deletions cpp/open3d/t/geometry/TriangleMesh.cpp
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Expand Up @@ -174,6 +174,81 @@ TriangleMesh &TriangleMesh::Rotate(const core::Tensor &R,
return *this;
}

TriangleMesh &TriangleMesh::RemoveDuplicatedTriangles() {
core::Tensor triangles = GetTriangleIndices();
int64_t num_triangles = triangles.GetLength();
if (num_triangles < 2) {
return *this;
}
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// unordered_map to keep track of existing triangles
// hash function with code::Tensor not implemented so we use std::tuple
typedef std::tuple<int64_t, int64_t, int64_t> Index3;
std::unordered_map<Index3, size_t, utility::hash_tuple<Index3>>
triangle_to_old_index;
std::vector<int64_t> triangle_vec;

// Check if mesh has normals triangles and colors
bool has_tri_normal = HasTriangleNormals();
bool has_tri_colors = HasTriangleColors();
bool find_dup = false;

// mask of triangles to keep
core::Tensor mask_of_triangles =
core::Tensor::Empty({num_triangles}, core::Bool, GetDevice());

for (int64_t i = 0; i < num_triangles; i++) {
Index3 triangle_in_tuple;
// Extract vertices of the triangle
core::Tensor triangle_to_check = triangles[i];

if (triangles.GetDtype() == core::Int32) {
auto vertice_0 = triangle_to_check[0].Item<int32_t>();
auto vertice_1 = triangle_to_check[1].Item<int32_t>();
auto vertice_2 = triangle_to_check[2].Item<int32_t>();
triangle_vec = {vertice_0, vertice_1, vertice_2};
} else if (triangles.GetDtype() == core::Int64) {
auto vertice_0 = triangle_to_check[0].Item<int64_t>();
auto vertice_1 = triangle_to_check[1].Item<int64_t>();
auto vertice_2 = triangle_to_check[2].Item<int64_t>();
triangle_vec = {vertice_0, vertice_1, vertice_2};
}

// We first need to find the minimum index. Because triangle (0-1-2)
// and triangle (2-0-1) are the same.
std::sort(triangle_vec.begin(), triangle_vec.end());
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Triangles / faces are directional, i.e. triangle {0,1,2} is different from triangle {2,1,0} since their surface normals will face in opposite directions. Instead of sort, we can use std::rotate(triangle_vec.begin(), ptr_to_min, triangle_vec.end()) This ensures direction is preserved.

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Also, repeated memory allocation as we create a new vector for each face should be avoided.

triangle_in_tuple = std::make_tuple(triangle_vec[0], triangle_vec[1],
triangle_vec[2]);

// check is triangle is already present in the mesh
if (triangle_to_old_index.find(triangle_in_tuple) ==
triangle_to_old_index.end()) {
mask_of_triangles[i] = true;
triangle_to_old_index[triangle_in_tuple] = i;
} else {
find_dup = true;
mask_of_triangles[i] = false;
}
}

// do this only if there are some triangles to remove
if (find_dup) {
TriangleMesh mesh_without_dup = SelectFacesByMask(mask_of_triangles);
SetTriangleIndices(mesh_without_dup.GetTriangleIndices());
if (has_tri_normal) {
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Can you support other triangle attributes? (e.g. triangle colors, etc.) An important feature of the Tensor API data structures is support for generic triangle and vertex attributes.

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Yes the triangle colors are manage in this : 3aa93dd

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We want to support arbitrary user defined attributes. Examples are labels, covariance, opacity, etc. See SelectFacesByMask for how to support arbitrary attributes.

core::Tensor tris =
GetTriangleNormals().IndexGet({mask_of_triangles});
SetTriangleNormals(tris);
}
if (has_tri_colors) {
core::Tensor colors =
GetTriangleColors().IndexGet({mask_of_triangles});
SetTriangleColors(colors);
}
}

return *this;
}

TriangleMesh &TriangleMesh::NormalizeNormals() {
if (HasVertexNormals()) {
SetVertexNormals(GetVertexNormals().Contiguous());
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4 changes: 4 additions & 0 deletions cpp/open3d/t/geometry/TriangleMesh.h
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Expand Up @@ -654,6 +654,10 @@ class TriangleMesh : public Geometry, public DrawableGeometry {
/// \return Rotated TriangleMesh
TriangleMesh &Rotate(const core::Tensor &R, const core::Tensor &center);

/// \brief Remove duplicated triangles from the TriangleMesh
/// \return TriangleMesh without duplicated triangles
TriangleMesh &RemoveDuplicatedTriangles();

/// Normalize both triangle normals and vertex normals to length 1.
TriangleMesh &NormalizeNormals();

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3 changes: 3 additions & 0 deletions cpp/pybind/t/geometry/trianglemesh.cpp
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Expand Up @@ -176,6 +176,9 @@ The attributes of the triangle mesh have different levels::
"Scale points.");
triangle_mesh.def("rotate", &TriangleMesh::Rotate, "R"_a, "center"_a,
"Rotate points and normals (if exist).");
triangle_mesh.def("remove_duplicated_triangles",
&TriangleMesh::RemoveDuplicatedTriangles,
"Remove duplicated triangles from a triangle");

triangle_mesh.def(
"normalize_normals", &TriangleMesh::NormalizeNormals,
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84 changes: 84 additions & 0 deletions cpp/tests/t/geometry/TriangleMesh.cpp
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Expand Up @@ -327,6 +327,90 @@ TEST_P(TriangleMeshPermuteDevices, Rotate) {
core::Tensor::Init<float>({{2, 2, 1}, {2, 2, 1}}, device)));
}

TEST_P(TriangleMeshPermuteDevices, RemoveDuplicatedTriangles) {
core::Device device = GetParam();

t::geometry::TriangleMesh mesh(device);

mesh.SetVertexPositions(core::Tensor::Init<float>({{0, 0, 0},
{1, 0, 0},
{0, 0, 1},
{1, 0, 1},
{0, 1, 0},
{1, 1, 0},
{0, 1, 1},
{1, 1, 1}},
device));

mesh.SetTriangleIndices(core::Tensor::Init<int64_t>({{4, 7, 5},
{4, 6, 7},
{0, 2, 4},
{2, 6, 4},
{0, 1, 2},
{1, 3, 2},
{1, 5, 7},
{1, 7, 3},
{2, 3, 7},
{2, 7, 6},
{4, 6, 7},
{0, 4, 1},
{1, 4, 5}},
device));

mesh.SetTriangleNormals(core::Tensor::Init<float>({{4, 7, 5},
{4, 6, 7},
{0, 2, 4},
{2, 6, 4},
{0, 1, 2},
{1, 3, 2},
{1, 5, 7},
{1, 7, 3},
{2, 3, 7},
{2, 7, 6},
{4, 6, 7},
{0, 4, 1},
{1, 4, 5}},
device));

mesh.SetTriangleColors(core::Tensor::Ones({13, 3}, core::Float32, device));

mesh.RemoveDuplicatedTriangles();

EXPECT_EQ(mesh.GetTriangleIndices().GetLength(), 12);
EXPECT_EQ(mesh.GetTriangleNormals().GetLength(), 12);
EXPECT_EQ(mesh.GetTriangleColors().GetLength(), 12);

EXPECT_TRUE(mesh.GetTriangleIndices().AllClose(
core::Tensor::Init<int64_t>({{4, 7, 5},
{4, 6, 7},
{0, 2, 4},
{2, 6, 4},
{0, 1, 2},
{1, 3, 2},
{1, 5, 7},
{1, 7, 3},
{2, 3, 7},
{2, 7, 6},
{0, 4, 1},
{1, 4, 5}},
device)));

EXPECT_TRUE(mesh.GetTriangleNormals().AllClose(
core::Tensor::Init<float>({{4, 7, 5},
{4, 6, 7},
{0, 2, 4},
{2, 6, 4},
{0, 1, 2},
{1, 3, 2},
{1, 5, 7},
{1, 7, 3},
{2, 3, 7},
{2, 7, 6},
{0, 4, 1},
{1, 4, 5}},
device)));
}

TEST_P(TriangleMeshPermuteDevices, NormalizeNormals) {
core::Device device = GetParam();

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26 changes: 26 additions & 0 deletions python/test/t/geometry/test_trianglemesh.py
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Expand Up @@ -417,3 +417,29 @@ def test_pickle(device):
mesh.vertex.positions.cpu().numpy())
np.testing.assert_equal(mesh_load.triangle.indices.cpu().numpy(),
mesh.triangle.indices.cpu().numpy())


@pytest.mark.parametrize("device", list_devices())
def test_remove_duplicated_triangles(device):

mesh = o3d.t.geometry.TriangleMesh()
vertex_positions = o3c.Tensor(
[[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 0.0, 1.0], [1.0, 0.0, 1.0],
[0.0, 1.0, 0.0], [1.0, 1.0, 0.0], [0.0, 1.0, 1.0], [1.0, 1.0, 1.0]],
o3c.float32, device)
triangle_indices = o3c.Tensor(
[[4, 7, 5], [4, 6, 7], [0, 2, 4], [2, 6, 4], [0, 1, 2], [1, 3, 2],
[1, 5, 7], [1, 7, 3], [2, 3, 7], [2, 7, 6], [4, 6, 7], [0, 4, 1],
[1, 4, 5]], o3c.int64, device)
mesh.vertex.positions = vertex_positions
mesh.triangle.indices = triangle_indices

mesh.remove_duplicated_triangles()

assert mesh.triangle.indices.shape == (12, 3)
np.testing.assert_allclose(
mesh.triangle.indices.cpu().numpy(),
o3c.Tensor(
[[4, 7, 5], [4, 6, 7], [0, 2, 4], [2, 6, 4], [0, 1, 2], [1, 3, 2],
[1, 5, 7], [1, 7, 3], [2, 3, 7], [2, 7, 6], [0, 4, 1], [1, 4, 5]],
o3c.int64, device).cpu().numpy())
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