Multires: Fix wrong or missing mask propagation

Propagation when changing sculpt level was missing. In fact, the mask
was simply completely removed when changing sculpt level.

Subdivision worked for simple and linear subdivision, but Catmull-Clark
was giving empty results.

Fixes propagation part of T76386.

1 files changed, 9 insertions, 5 deletions

diff --git a/source/blender/blenkernel/intern/multires_reshape_util.c b/source/blender/blenkernel/intern/multires_reshape_util.c
index fcee98da1c5..e9a779dafeb 100644
--- a/source/blender/blenkernel/intern/multires_reshape_util.c
+++ b/source/blender/blenkernel/intern/multires_reshape_util.c
@@ -751,9 +751,9 @@ void multires_reshape_assign_final_coords_from_mdisps(
       reshape_context, reshape_context->top.level, assign_final_coords_from_mdisps, NULL);
 }
 
-static void assign_final_coords_from_orig_mdisps(const MultiresReshapeContext *reshape_context,
-                                                 const GridCoord *grid_coord,
-                                                 void *UNUSED(userdata_v))
+static void assign_final_elements_from_orig_mdisps(const MultiresReshapeContext *reshape_context,
+                                                   const GridCoord *grid_coord,
+                                                   void *UNUSED(userdata_v))
 {
   float P[3];
   float tangent_matrix[3][3];
@@ -768,13 +768,17 @@ static void assign_final_coords_from_orig_mdisps(const MultiresReshapeContext *r
   ReshapeGridElement grid_element = multires_reshape_grid_element_for_grid_coord(reshape_context,
                                                                                  grid_coord);
   add_v3_v3v3(grid_element.displacement, P, D);
+
+  if (grid_element.mask != NULL) {
+    *grid_element.mask = orig_grid_element.mask;
+  }
 }
 
-void multires_reshape_assign_final_coords_from_orig_mdisps(
+void multires_reshape_assign_final_elements_from_orig_mdisps(
     const MultiresReshapeContext *reshape_context)
 {
   foreach_grid_coordinate(
-      reshape_context, reshape_context->top.level, assign_final_coords_from_orig_mdisps, NULL);
+      reshape_context, reshape_context->top.level, assign_final_elements_from_orig_mdisps, NULL);
 }
 
 /** \} */