Fix T50534: Part I, cleanup loop normals generated during modifier stack evaluation.

Those could stay around, and be displayed in 3DView even when autosmooth
was disabled (but would not be 'active').

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/DerivedMesh.c b/source/blender/blenkernel/intern/DerivedMesh.c
index 1f937d837b4..160adcc3988 100644
--- a/source/blender/blenkernel/intern/DerivedMesh.c
+++ b/source/blender/blenkernel/intern/DerivedMesh.c
@@ -2215,6 +2215,12 @@ static void mesh_calc_modifiers(
 		}
 	}
 
+	/* Some modifiers, like datatransfer, may generate those data as temp layer, we do not want to keep them,
+	 * as they are used by display code when available (i.e. even if autosmooth is disabled). */
+	if (!do_loop_normals && CustomData_has_layer(&finaldm->loopData, CD_NORMAL)) {
+		CustomData_free_layers(&finaldm->loopData, CD_NORMAL, finaldm->numLoopData);
+	}
+
 #ifdef WITH_GAMEENGINE
 	/* NavMesh - this is a hack but saves having a NavMesh modifier */
 	if ((ob->gameflag & OB_NAVMESH) && (finaldm->type == DM_TYPE_CDDM)) {
@@ -2550,6 +2556,15 @@ static void editbmesh_calc_modifiers(
 	/* same as mesh_calc_modifiers (if using loop normals, poly nors have already been computed). */
 	if (!do_loop_normals) {
 		dm_ensure_display_normals(*r_final);
+
+		/* Some modifiers, like datatransfer, may generate those data, we do not want to keep them,
+		 * as they are used by display code when available (i.e. even if autosmooth is disabled). */
+		if (CustomData_has_layer(&(*r_final)->loopData, CD_NORMAL)) {
+			CustomData_free_layers(&(*r_final)->loopData, CD_NORMAL, (*r_final)->numLoopData);
+		}
+		if (r_cage && CustomData_has_layer(&(*r_cage)->loopData, CD_NORMAL)) {
+			CustomData_free_layers(&(*r_cage)->loopData, CD_NORMAL, (*r_cage)->numLoopData);
+		}
 	}
 
 	/* add an orco layer if needed */