Implement open3d::t::geometry::TriangleMesh::SelectByIndex #6415
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| // really copy triangles to CPU as we will modify the indices | ||
| core::Tensor tris_cpu = | ||
| GetTriangleIndices().To(core::Device(), true).Contiguous(); |
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The true argument here makes the "true" copy, which the SelectFacesByMask does not do. In my case, if I don't have it, the triangles do not match the original mesh if the device is CPU.
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(...,/*copy=*/true) is a good way to indicate the name of the argument you are supplying.
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which the SelectFacesByMask does not do
Not a problem at SelectFacesByMask, as it already operates on a copy made by GetIndex(mask).
After extracting the common parts with SelectFacesByMask, I also stopped needing the true copy.
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Comment updated on 17.10.2023
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| // really copy triangles to CPU as we will modify the indices | ||
| core::Tensor tris_cpu = | ||
| GetTriangleIndices().To(core::Device(), true).Contiguous(); |
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(...,/*copy=*/true) is a good way to indicate the name of the argument you are supplying.
| core::AssertTensorShape(indices, {indices.GetLength()}); | ||
| if (!HasTriangleIndices()) { | ||
| utility::LogError("[SelectByIndex] mesh has no triangle indices."); | ||
| } | ||
| if (!HasVertexPositions()) { | ||
| utility::LogError("[SelectByIndex] mesh has no vertex positions."); | ||
| } |
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We can return an empty mesh for corner case such as when indices are empty.
This is a helper to call a templated function with an integer argument,
based on Dtype. As a second argument, it takes a suffix, used to build
a unique type name. This way, we can use it to call a function with
more than one integer argument.
Example:
DISPATCH_INT_DTYPE_PREFIX_TO_TEMPLATE(core::Dtype::Int32, int32, [&]() {
DISPATCH_INT_DTYPE_PREFIX_TO_TEMPLATE(core::Dtype::UInt64, uint64, [&]() {
scalar_int32_t a;
scalar_uint64_t b;
// ...
});
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The method takes a list of indices and returns a new mesh built with the selected vertices and triangles formed by these vertices. The indices type can be any integral type. The algorithm is implemented on CPU only. The implementation is inspired by open3d::geometry::TriangleMesh::SelectByIndex. and by open3d::t::geometry::TriangleMesh::SelectFacesByMask. We first compute a mask of vertices to be selected. If the input index exceeds the maximum number of vertices or is negative, we ignore the index and print a warning. If the mesh has triangles, we build tringle mask and select needed triangles. The next step is to update triangle indices to a new ones. It is similar to SelectFacesByMask, so I introduced a static helper to do that. Based on the vertex mask we build a mapping index vector using inclusive prefix sum algorithm and use it as a map between old and new indices. We select the vertices by mask and build the resulting mesh from the selected vertices and triangles. Copying the mesh attributes is again similar to SelectFacesByMask, so I put it to a separate static function.
* Add error handling on empty mesh * Use DISPATCH_INT_DTYPE_PREFIX_TO_TEMPLATE instead of a conditional branch * Use UpdateTriangleIndicesByVertexMask helper to update triangle indices * Use CopyAttributesByMask helper to copy the mesh attributes * Add tests
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@ssheorey I am not exactly sure why the CI fails, this link does not give me the clarity: https://github.com/isl-org/Open3D/actions/runs/6798298171/job/18482179687?pr=6415. Could you please help me to find out whether it is caused by my PR? |
The method uses tensor API. It takes a list of indices and returns a new mesh built with the selected vertices and triangles formed by these vertices.
Type
Motivation and Context
The method is available with the
open3d::geometry::TriangleMeshbut not inopen3d::t::geometry::TriangleMesh.Checklist:
python util/check_style.py --applyto apply Open3D code styleto my code.
updated accordingly. <---- here I am not sure about the Python doc, as I could not generate it locally.
results (e.g. screenshots or numbers) here.
Description
The implementation is inspired by
open3d::geometry::TriangleMesh::SelectByIndex.
and by
open3d::t::geometry::TriangleMesh::SelectFacesByMask.
We first compute a mask of vertices to be selected. If the input index exceeds the maximum number of vertices, we throw an exception. Based on the vertex mask we build a mapping index vector using inclusive prefix sum algorithm. We then update the selected vertex indices in the triangles CPU copy and build the triangles mask. I put that to a templated helper static function to avoid the code duplication for Int32 and Int64 vertex indices types.
With the computed masks we can select the vertices and triangles back on the mesh's device and copy the attributes.
FYI @ssheorey
This change is