[Bf-blender-cvs] [63e64940f32] usd-importer-T81257-merge: USD import: bug detecting mesh topology change

[makowalski]

Commit: 63e64940f327565e68ab80388856f49e5e427d00
Author: makowalski
Date:   Mon Jul 26 21:42:56 2021 -0400
Branches: usd-importer-T81257-merge
https://developer.blender.org/rB63e64940f327565e68ab80388856f49e5e427d00

USD import: bug detecting mesh topology change

Fixed mesh reader logic detecting topology changes in mesh
sequence animations, which avoids a crash in some cases.

===================================================================

M	source/blender/io/usd/intern/usd_reader_mesh.cc
M	source/blender/io/usd/intern/usd_reader_mesh.h

===================================================================

diff --git a/source/blender/io/usd/intern/usd_reader_mesh.cc b/source/blender/io/usd/intern/usd_reader_mesh.cc
index c1e0152a808..6fe79249583 100644
--- a/source/blender/io/usd/intern/usd_reader_mesh.cc
+++ b/source/blender/io/usd/intern/usd_reader_mesh.cc
@@ -183,7 +183,6 @@ USDMeshReader::USDMeshReader(const pxr::UsdPrim &prim,
     : USDGeomReader(prim, import_params, settings),
       mesh_prim_(prim),
       is_left_handed_(false),
-      last_num_positions_(-1),
       has_uvs_(false),
       is_time_varying_(false),
       is_initial_load_(false)
@@ -242,18 +241,14 @@ bool USDMeshReader::valid() const
   return static_cast<bool>(mesh_prim_);
 }
 
-bool USDMeshReader::topology_changed(Mesh * /* existing_mesh */, const double motionSampleTime)
+bool USDMeshReader::topology_changed(Mesh *existing_mesh, const double motionSampleTime)
 {
   /* TODO(makowalski): Is it the best strategy to cache the mesh
    * geometry in this function?  This needs to be revisited. */
-  pxr::UsdAttribute faceVertCountsAttr = mesh_prim_.GetFaceVertexCountsAttr();
-  pxr::UsdAttribute faceVertIndicesAttr = mesh_prim_.GetFaceVertexIndicesAttr();
-  pxr::UsdAttribute pointsAttr = mesh_prim_.GetPointsAttr();
-  pxr::UsdAttribute normalsAttr = mesh_prim_.GetNormalsAttr();
 
-  faceVertIndicesAttr.Get(&face_indices_, motionSampleTime);
-  faceVertCountsAttr.Get(&face_counts_, motionSampleTime);
-  pointsAttr.Get(&positions_, motionSampleTime);
+  mesh_prim_.GetFaceVertexIndicesAttr().Get(&face_indices_, motionSampleTime);
+  mesh_prim_.GetFaceVertexCountsAttr().Get(&face_counts_, motionSampleTime);
+  mesh_prim_.GetPointsAttr().Get(&positions_, motionSampleTime);
 
   /* If 'normals' and 'primvars:normals' are both specified, the latter has precedence. */
   pxr::UsdGeomPrimvar primvar = mesh_prim_.GetPrimvar(usdtokens::normalsPrimvar);
@@ -266,15 +261,9 @@ bool USDMeshReader::topology_changed(Mesh * /* existing_mesh */, const double mo
     normal_interpolation_ = mesh_prim_.GetNormalsInterpolation();
   }
 
-  /* TODO(makowalski): Why aren't we comparing positions_.size()
-   * against the number of points of the existing_mesh?
-   * Why keep track of the last_num_positons_ at all? */
-  if (last_num_positions_ != positions_.size()) {
-    last_num_positions_ = positions_.size();
-    return true;
-  }
-
-  return false;
+  return positions_.size() != existing_mesh->totvert ||
+         face_counts_.size() != existing_mesh->totpoly ||
+         face_indices_.size() != existing_mesh->totloop;
 }
 
 void USDMeshReader::read_mpolys(Mesh *mesh)
diff --git a/source/blender/io/usd/intern/usd_reader_mesh.h b/source/blender/io/usd/intern/usd_reader_mesh.h
index 71c0860454c..43c812fdb89 100644
--- a/source/blender/io/usd/intern/usd_reader_mesh.h
+++ b/source/blender/io/usd/intern/usd_reader_mesh.h
@@ -42,7 +42,6 @@ class USDMeshReader : public USDGeomReader {
   pxr::TfToken normal_interpolation_;
   pxr::TfToken orientation_;
   bool is_left_handed_;
-  int last_num_positions_;
   bool has_uvs_;
   bool is_time_varying_;