Fix T52149: LoopTriArray computation was not correctly protected against concurrency.

Note: this commit seems to work as expected (also with transform
snapping etc.). However, it is rather unsafe - not enough for 2.79 at
least, unless we get much more testing on it. It also depends on three
previous ones.

Note that using a global lock here is far from ideal, we should rather
have a lock per DM, but that will do for now, whole DM thing is doomed
to oblivion anyway in 2.8.

Also, we may need a `DM_DIRTY_LOOPTRIS` dirty flag at some point. Looks
like we can survive without it for now though... Probably because cached
looptris are never copied accross DM's?

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_DerivedMesh.h b/source/blender/blenkernel/BKE_DerivedMesh.h
index 5a4fdcf2510..e2577689101 100644
--- a/source/blender/blenkernel/BKE_DerivedMesh.h
+++ b/source/blender/blenkernel/BKE_DerivedMesh.h
@@ -220,7 +220,7 @@ struct DerivedMesh {
 	/** Recalculates mesh tessellation */
 	void (*recalcTessellation)(DerivedMesh *dm);
 
-	/** Loop tessellation cache */
+	/** Loop tessellation cache (WARNING! Only call inside threading-protected code!) */
 	void (*recalcLoopTri)(DerivedMesh *dm);
 	/** accessor functions */
 	const struct MLoopTri *(*getLoopTriArray)(DerivedMesh * dm);