avoid recalculating normals for simple move

Summary: If offset_verts_ is used to move meshes with a single vector, the normals won't change so don't need to recalculate. I am planning to allow user-specified vertex normals. This change means that user-specified vertex normals won't get overwritten when they don't need to be.

Reviewed By: nikhilaravi

Differential Revision: D27765256

fbshipit-source-id: f6e4d308ac9ac023030325cb75a18d39b966cf88

pytorch3d/structures/meshes.py

@@ -1263,7 +1263,10 @@ def offset_verts_(self, vert_offsets_packed):
         """
         verts_packed = self.verts_packed()
         if vert_offsets_packed.shape == (3,):
+            update_normals = False
             vert_offsets_packed = vert_offsets_packed.expand_as(verts_packed)
+        else:
+            update_normals = True
         if vert_offsets_packed.shape != verts_packed.shape:
             raise ValueError("Verts offsets must have dimension (all_v, 3).")
         # update verts packed
@@ -1284,12 +1287,12 @@ def offset_verts_(self, vert_offsets_packed):
 
         # update face areas and normals and vertex normals
         # only if the original attributes are computed
-        if any(
+        if update_normals and any(
             v is not None
             for v in [self._faces_areas_packed, self._faces_normals_packed]
         ):
             self._compute_face_areas_normals(refresh=True)
-        if self._verts_normals_packed is not None:
+        if update_normals and self._verts_normals_packed is not None:
             self._compute_vertex_normals(refresh=True)
 
         return self

tests/test_meshes.py

@@ -486,6 +486,7 @@ def naive_offset_verts(mesh, vert_offsets_packed):
                 self.assertClose(
                     new_mesh.verts_normals_list()[i],
                     new_mesh_naive.verts_normals_list()[i],
+                    atol=1e-6,
                 )
                 self.assertClose(
                     new_mesh.faces_normals_list()[i],
@@ -533,10 +534,14 @@ def naive_offset_verts(mesh, vert_offsets_packed):
 
             # check face areas, normals and vertex normals
             self.assertClose(
-                new_mesh.verts_normals_packed(), new_mesh_naive.verts_normals_packed()
+                new_mesh.verts_normals_packed(),
+                new_mesh_naive.verts_normals_packed(),
+                atol=1e-6,
             )
             self.assertClose(
-                new_mesh.verts_normals_padded(), new_mesh_naive.verts_normals_padded()
+                new_mesh.verts_normals_padded(),
+                new_mesh_naive.verts_normals_padded(),
+                atol=1e-6,
             )
             self.assertClose(
                 new_mesh.faces_normals_packed(), new_mesh_naive.faces_normals_packed()