When these features aren't used, there is no sense in storing the

corresponding data layers and using their values for computations.
Avoiding that should increase performance in many operations that
would otherwise have to read, write, or propagate these values.
It also means decreased memory usage-- not just for sculpt mode
but for any mesh that was in sculpt mode. Previously the mask, face set,
and hide status layers were *always* allocated by sculpt mode.

Here are a few basic tests when masking and face sets are not used:

| Test | Before | After |
| Subsurf Modifier | 148 ms | 126 ms |
| Sculpt Overlay Extraction | 24 ms every redraw | 0 ms |
| Memory usage | 252 MB | 236 MB |

I wouldn't expect any difference when they are used though.

The code changes are mostly just making sculpt features safe for when
the layers aren't stored, and some changes to the conversion to and
from the hide layers. Use of the ".hide_poly" attribute replaces testing
whether face sets are negative in many places.

Differential Revision: https://developer.blender.org/D15937

1 files changed, 17 insertions, 15 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_ops.c b/source/blender/editors/sculpt_paint/sculpt_ops.c
index 10a2ece73de..055e02a5703 100644
--- a/source/blender/editors/sculpt_paint/sculpt_ops.c
+++ b/source/blender/editors/sculpt_paint/sculpt_ops.c
@@ -300,28 +300,30 @@ static void sculpt_init_session(Main *bmain, Depsgraph *depsgraph, Scene *scene,
   ob->sculpt = MEM_callocN(sizeof(SculptSession), "sculpt session");
   ob->sculpt->mode_type = OB_MODE_SCULPT;
 
-  BKE_sculpt_ensure_orig_mesh_data(scene, ob);
+  BKE_sculpt_ensure_orig_mesh_data(ob);
 
   BKE_scene_graph_evaluated_ensure(depsgraph, bmain);
 
   /* This function expects a fully evaluated depsgraph. */
   BKE_sculpt_update_object_for_edit(depsgraph, ob, false, false, false);
 
-  /* Here we can detect geometry that was just added to Sculpt Mode as it has the
-   * SCULPT_FACE_SET_NONE assigned, so we can create a new Face Set for it. */
-  /* In sculpt mode all geometry that is assigned to SCULPT_FACE_SET_NONE is considered as not
-   * initialized, which is used is some operators that modify the mesh topology to perform certain
-   * actions in the new polys. After these operations are finished, all polys should have a valid
-   * face set ID assigned (different from SCULPT_FACE_SET_NONE) to manage their visibility
-   * correctly. */
-  /* TODO(pablodp606): Based on this we can improve the UX in future tools for creating new
-   * objects, like moving the transform pivot position to the new area or masking existing
-   * geometry. */
   SculptSession *ss = ob->sculpt;
-  const int new_face_set = SCULPT_face_set_next_available_get(ss);
-  for (int i = 0; i < ss->totfaces; i++) {
-    if (ss->face_sets[i] == SCULPT_FACE_SET_NONE) {
-      ss->face_sets[i] = new_face_set;
+  if (ss->face_sets) {
+    /* Here we can detect geometry that was just added to Sculpt Mode as it has the
+     * SCULPT_FACE_SET_NONE assigned, so we can create a new Face Set for it. */
+    /* In sculpt mode all geometry that is assigned to SCULPT_FACE_SET_NONE is considered as not
+     * initialized, which is used is some operators that modify the mesh topology to perform
+     * certain actions in the new polys. After these operations are finished, all polys should have
+     * a valid face set ID assigned (different from SCULPT_FACE_SET_NONE) to manage their
+     * visibility correctly. */
+    /* TODO(pablodp606): Based on this we can improve the UX in future tools for creating new
+     * objects, like moving the transform pivot position to the new area or masking existing
+     * geometry. */
+    const int new_face_set = SCULPT_face_set_next_available_get(ss);
+    for (int i = 0; i < ss->totfaces; i++) {
+      if (ss->face_sets[i] == SCULPT_FACE_SET_NONE) {
+        ss->face_sets[i] = new_face_set;
+      }
     }
   }
 }