TexturesVertex._num_verts_per_mesh deep copy (#623)

Summary:
When a list of Meshes is `join_batched()`, the `num_verts_per_mesh` in the list would be unexpectedly modified.

Also some cleanup around `_num_verts_per_mesh`.

Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/623

Test Plan: A modification to an existing test checks this.

Reviewed By: nikhilaravi

Differential Revision: D27682104

Pulled By: bottler

fbshipit-source-id: 9d00913dfb4869bd6c7d3f5cc9156b7b6f1aecc9

pytorch3d/renderer/mesh/textures.py

@@ -842,8 +842,7 @@ class TexturesUV(TexturesBase):
             else:
                 # The number of vertices in the mesh and in verts_uvs can differ
                 # e.g. if a vertex is shared between 3 faces, it can
-                # have up to 3 different uv coordinates. Therefore we cannot
-                # convert directly from padded to list using _num_verts_per_mesh
+                # have up to 3 different uv coordinates.
                 self._verts_uvs_list = list(self._verts_uvs_padded.unbind(0))
         return self._verts_uvs_list
 
@@ -1283,12 +1282,7 @@ class TexturesVertex(TexturesBase):
         tex = self.__class__(self.verts_features_padded().clone())
         if self._verts_features_list is not None:
             tex._verts_features_list = [f.clone() for f in self._verts_features_list]
-        num_verts = (
-            self._num_verts_per_mesh.clone()
-            if torch.is_tensor(self._num_verts_per_mesh)
-            else self._num_verts_per_mesh
-        )
-        tex._num_verts_per_mesh = num_verts
+        tex._num_verts_per_mesh = self._num_verts_per_mesh.copy()
         tex.valid = self.valid.clone()
         return tex
 
@@ -1296,12 +1290,7 @@ class TexturesVertex(TexturesBase):
         tex = self.__class__(self.verts_features_padded().detach())
         if self._verts_features_list is not None:
             tex._verts_features_list = [f.detach() for f in self._verts_features_list]
-        num_verts = (
-            self._num_verts_per_mesh.detach()
-            if torch.is_tensor(self._num_verts_per_mesh)
-            else self._num_verts_per_mesh
-        )
-        tex._num_verts_per_mesh = num_verts
+        tex._num_verts_per_mesh = self._num_verts_per_mesh.copy()
         tex.valid = self.valid.detach()
         return tex
 
@@ -1414,13 +1403,13 @@ class TexturesVertex(TexturesBase):
 
         verts_features_list = []
         verts_features_list += self.verts_features_list()
-        num_faces_per_mesh = self._num_verts_per_mesh
+        num_verts_per_mesh = self._num_verts_per_mesh.copy()
         for tex in textures:
             verts_features_list += tex.verts_features_list()
-            num_faces_per_mesh += tex._num_verts_per_mesh
+            num_verts_per_mesh += tex._num_verts_per_mesh
 
         new_tex = self.__class__(verts_features=verts_features_list)
-        new_tex._num_verts_per_mesh = num_faces_per_mesh
+        new_tex._num_verts_per_mesh = num_verts_per_mesh
         return new_tex
 
     def join_scene(self) -> "TexturesVertex":

tests/test_io_obj.py

@@ -786,6 +786,11 @@ class TestMeshObjIO(TestCaseMixin, unittest.TestCase):
         mesh_rgb = Meshes(verts=[verts], faces=[faces], textures=rgb_tex)
         mesh_rgb3 = join_meshes_as_batch([mesh_rgb, mesh_rgb, mesh_rgb])
         check_triple(mesh_rgb, mesh_rgb3)
+        nums_rgb = mesh_rgb.textures._num_verts_per_mesh
+        nums_rgb3 = mesh_rgb3.textures._num_verts_per_mesh
+        self.assertEqual(type(nums_rgb), list)
+        self.assertEqual(type(nums_rgb3), list)
+        self.assertListEqual(nums_rgb * 3, nums_rgb3)
 
         # meshes with texture atlas, join into a batch.
         device = "cuda:0"