Fix T84202: Sculpt lasso mask crash after remesh.

'Caused'/revealed by rBd29a720c45e5: Operators that fully re-create the
mesh would previously rely on `sculpt_update_object` called from update
code to get required sculpt-specific data layers re-added to the new
mesh.

Now instead put all code adding data to orig mesh for sculpt purpose
into a new util function (`BKE_sculpt_ensure_orig_mesh_data`), and call
that function when entering sculpt mode, and from voxel remesher code.

This is contonuing effort to more clearly separate orig data from evaluated
data handling/usage in sculpt code.

TODO: there are likely other code paths that would need to call that
new function?

Reviewers: @sergey, @pablodp606

Subscribers:

1 files changed, 45 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/paint.c b/source/blender/blenkernel/intern/paint.c
index 7c2fc40d537..4eecf3a3a87 100644
--- a/source/blender/blenkernel/intern/paint.c
+++ b/source/blender/blenkernel/intern/paint.c
@@ -2021,6 +2021,51 @@ void BKE_sculpt_sync_face_set_visibility(struct Mesh *mesh, struct SubdivCCG *su
   BKE_sculpt_sync_face_sets_visibility_to_grids(mesh, subdiv_ccg);
 }
 
+/**
+ * Ensures we do have expected mesh data in original mesh for the sculpt mode.
+ *
+ * \note IDs are expected to be original ones here, and calling code should ensure it updates its
+ * depsgraph properly after calling this function if it needs up-to-date evaluated data.
+ */
+void BKE_sculpt_ensure_orig_mesh_data(Scene *scene, Object *object)
+{
+  Mesh *mesh = BKE_mesh_from_object(object);
+  MultiresModifierData *mmd = BKE_sculpt_multires_active(scene, object);
+
+  BLI_assert(object->mode == OB_MODE_SCULPT);
+
+  /* Copy the current mesh visibility to the Face Sets. */
+  BKE_sculpt_face_sets_ensure_from_base_mesh_visibility(mesh);
+  if (object->sculpt != NULL) {
+    /* If a sculpt session is active, ensure we have its faceset data porperly up-to-date. */
+    object->sculpt->face_sets = CustomData_get_layer(&mesh->pdata, CD_SCULPT_FACE_SETS);
+
+    /* Note: In theory we could add that on the fly when required by sculpt code.
+     * But this then requires proper update of depsgraph etc. For now we play safe, optimization is
+     * always possible later if it's worth it. */
+    BKE_sculpt_mask_layers_ensure(object, mmd);
+  }
+
+  /* Tessfaces aren't used and will become invalid. */
+  BKE_mesh_tessface_clear(mesh);
+
+  /* We always need to flush updates from depsgraph here, since at the very least
+   * `BKE_sculpt_face_sets_ensure_from_base_mesh_visibility()` will have updated some data layer of
+   * the mesh.
+   *
+   * All known potential sources of updates:
+   *   - Addition of, or changes to, the `CD_SCULPT_FACE_SETS` data layer
+   *     (`BKE_sculpt_face_sets_ensure_from_base_mesh_visibility`).
+   *   - Addition of a `CD_PAINT_MASK` data layer (`BKE_sculpt_mask_layers_ensure`).
+   *   - Object has any active modifier (modifier stack can be different in Sculpt mode).
+   *   - Multires:
+   *     + Differences of subdiv levels between sculpt and object modes
+   *       (`mmd->sculptlvl != mmd->lvl`).
+   *     + Addition of a `CD_GRID_PAINT_MASK` data layer (`BKE_sculpt_mask_layers_ensure`).
+   */
+  DEG_id_tag_update(&object->id, ID_RECALC_GEOMETRY);
+}
+
 static PBVH *build_pbvh_for_dynamic_topology(Object *ob)
 {
   PBVH *pbvh = BKE_pbvh_new();