Fix T57652: Multires undo broken with shared object data

1 files changed, 11 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/multires.c b/source/blender/blenkernel/intern/multires.c
index 17d6b623b33..29337ca9985 100644
--- a/source/blender/blenkernel/intern/multires.c
+++ b/source/blender/blenkernel/intern/multires.c
@@ -385,12 +385,20 @@ static void multires_ccg_mark_as_modified(SubdivCCG *subdiv_ccg, MultiresModifie
   }
 }
 
-void multires_mark_as_modified(Object *ob, MultiresModifiedFlags flags)
+void multires_mark_as_modified(Depsgraph *depsgraph, Object *object, MultiresModifiedFlags flags)
 {
-  if (ob == NULL) {
+  if (object == NULL) {
     return;
   }
-  Mesh *mesh = ob->data;
+  /* NOTE: CCG live inside of evaluated object.
+   *
+   * While this is a bit weird to tag the only one, this is how other areas were built
+   * historically: they are tagging multires for update and then rely on object re-evaluation to
+   * do an actual update.
+   *
+   * In a longer term maybe special dependency graph tag can help sanitizing this a bit. */
+  Object *object_eval = DEG_get_evaluated_object(depsgraph, object);
+  Mesh *mesh = object_eval->data;
   SubdivCCG *subdiv_ccg = mesh->runtime.subdiv_ccg;
   if (subdiv_ccg == NULL) {
     return;