Fix T96338: GPU subdiv crash switching to UV editing

The crash is caused as the data for the UV editor is requested before
the data for the mesh as a separate draw update. Since building the UV
stretch angle buffer requires the position buffer, the latter is not
created yet in this case.

To fix this, create a local position buffer from the subdivision data. An
alternate fix was considered to remove the dependency on the position
buffer by interpolating on the GPU the coarse stretch angle buffer but
this did work. Maybe this will be revisited.

1 files changed, 1 insertions, 12 deletions

diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_pos_nor.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_pos_nor.cc
index dd056891a94..ea46d9c4caa 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_pos_nor.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_pos_nor.cc
@@ -179,17 +179,6 @@ static void extract_pos_nor_finish(const MeshRenderData *UNUSED(mr),
   MEM_freeN(data->normals);
 }
 
-static GPUVertFormat *get_pos_nor_format()
-{
-  static GPUVertFormat format = {0};
-  if (format.attr_len == 0) {
-    GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
-    GPU_vertformat_attr_add(&format, "nor", GPU_COMP_F32, 4, GPU_FETCH_FLOAT);
-    GPU_vertformat_alias_add(&format, "vnor");
-  }
-  return &format;
-}
-
 static GPUVertFormat *get_normals_format()
 {
   static GPUVertFormat format = {0};
@@ -221,7 +210,7 @@ static void extract_pos_nor_init_subdiv(const DRWSubdivCache *subdiv_cache,
 
   /* Initialize the vertex buffer, it was already allocated. */
   GPU_vertbuf_init_build_on_device(
-      vbo, get_pos_nor_format(), subdiv_cache->num_subdiv_loops + loose_geom.loop_len);
+      vbo, draw_subdiv_get_pos_nor_format(), subdiv_cache->num_subdiv_loops + loose_geom.loop_len);
 
   if (subdiv_cache->num_subdiv_loops == 0) {
     return;