Fix T95334: Crash with no vertex normals in multires bake

This is partially caused by a stupid mistake in cfa53e0fbeed7178c78
where I missed initializing the `vert_normals` pointer in
`MResolvePixelData`. It's also caused by questionable assumptions
from DerivedMesh code that vertex normals would be valid.

The fix used here is to create a temporary mesh with the data necessary
to compute vertex normals, and ensure them here. This is used because
normal calculation is only implemented for `Mesh` and edit mesh, not
`DerivedMesh`. While this might not be great for performance, it's
potentially aligned with future refactoring of this code to remove
`DerivedMesh` completely. Since this is one of the last places the data
structure is used, that would be a great improvement.

Differential Revision: https://developer.blender.org/D13960

1 files changed, 0 insertions, 5 deletions

diff --git a/source/blender/blenkernel/BKE_DerivedMesh.h b/source/blender/blenkernel/BKE_DerivedMesh.h
index ef9711c360c..4526bc38a70 100644
--- a/source/blender/blenkernel/BKE_DerivedMesh.h
+++ b/source/blender/blenkernel/BKE_DerivedMesh.h
@@ -334,11 +334,6 @@ void makeDerivedMesh(struct Depsgraph *depsgraph,
                      struct Object *ob,
                      const struct CustomData_MeshMasks *dataMask);
 
-void DM_calc_loop_tangents(DerivedMesh *dm,
-                           bool calc_active_tangent,
-                           const char (*tangent_names)[MAX_NAME],
-                           int tangent_names_len);
-
 #ifdef __cplusplus
 }
 #endif