Depsgraph API: Allow preserving custom data layers

This commit extends dependency graph API with an argument which
denotes that all custom data layers are to be preserved. This
forces modifier stack re-evaluation with more inclusive mask.

Far from ideal, since this might fail in certain configurations
with indirectly used objects which might be missing layers needed
for the current object evaluation. But this is how it worked for
a long time, so should be good enough for until more sophisticated
solution is found.

In order to use this new behavior two things are to be passed:

- Pass keep_all_data_layers=True
- Pass a valid dependency graph.

The dependency graph is only needed if keep_all_data_layers=True
and is NOT to be passed if keep_all_data_layers=False.

If keep_all_data_layers=True the dependency graph MUST be passed.

Reviewers: mont29, brecht

Reviewed By: mont29

Maniphest Tasks: T64994, T64794

Differential Revision: https://developer.blender.org/D4940

4 files changed, 80 insertions, 19 deletions

diff --git a/source/blender/blenkernel/BKE_mesh.h b/source/blender/blenkernel/BKE_mesh.h
index c410946f438..54fbda1fa31 100644
--- a/source/blender/blenkernel/BKE_mesh.h
+++ b/source/blender/blenkernel/BKE_mesh.h
@@ -209,11 +209,22 @@ float (*BKE_mesh_vertexCos_get(const struct Mesh *me, int *r_numVerts))[3];
 void BKE_mesh_split_faces(struct Mesh *mesh, bool free_loop_normals);
 
 /* Create new mesh from the given object at its current state.
- * The owner of this mesh is unknown, it is up to the caller to decide. */
-struct Mesh *BKE_mesh_new_from_object(struct Object *object);
+ * The owner of this mesh is unknown, it is up to the caller to decide.
+ *
+ * If preserve_all_data_layers is truth then the modifier stack is re-evaluated to ensure it
+ * preserves all possible custom data layers.
+ *
+ * NOTE: Dependency graph argument is required when preserve_all_data_layers is truth, and is
+ * ignored otherwise. */
+struct Mesh *BKE_mesh_new_from_object(struct Depsgraph *depsgraph,
+                                      struct Object *object,
+                                      bool preserve_all_data_layers);
 
 /* This is a version of BKE_mesh_new_from_object() which stores mesh in the given main database. */
-struct Mesh *BKE_mesh_new_from_object_to_bmain(struct Main *bmain, struct Object *object);
+struct Mesh *BKE_mesh_new_from_object_to_bmain(struct Main *bmain,
+                                               struct Depsgraph *depsgraph,
+                                               struct Object *object,
+                                               bool preserve_all_data_layers);
 
 struct Mesh *BKE_mesh_create_derived_for_modifier(struct Depsgraph *depsgraph,
                                                   struct Scene *scene,
diff --git a/source/blender/blenkernel/BKE_object.h b/source/blender/blenkernel/BKE_object.h
index aa4d9696527..df1ac0e4081 100644
--- a/source/blender/blenkernel/BKE_object.h
+++ b/source/blender/blenkernel/BKE_object.h
@@ -400,8 +400,16 @@ bool BKE_object_empty_image_data_is_visible_in_view3d(const struct Object *ob,
  * The result is owned by the object.
  *
  * The mesh will be freed when object is re-evaluated or is destroyed. It is possible to force to
- * clear memory sued by this mesh by calling BKE_object_to_mesh_clear(). */
-struct Mesh *BKE_object_to_mesh(struct Object *object);
+ * clear memory sued by this mesh by calling BKE_object_to_mesh_clear().
+ *
+ * If preserve_all_data_layers is truth then the modifier stack is re-evaluated to ensure it
+ * preserves all possible custom data layers.
+ *
+ * NOTE: Dependency graph argument is required when preserve_all_data_layers is truth, and is
+ * ignored otherwise. */
+struct Mesh *BKE_object_to_mesh(struct Depsgraph *depsgraph,
+                                struct Object *object,
+                                bool preserve_all_data_layers);
 
 void BKE_object_to_mesh_clear(struct Object *object);
 
diff --git a/source/blender/blenkernel/intern/mesh_convert.c b/source/blender/blenkernel/intern/mesh_convert.c
index 461adc823b9..c7ddb8628f9 100644
--- a/source/blender/blenkernel/intern/mesh_convert.c
+++ b/source/blender/blenkernel/intern/mesh_convert.c
@@ -1082,17 +1082,11 @@ static Mesh *mesh_new_from_mball_object(Object *object)
   return mesh_result;
 }
 
-static Mesh *mesh_new_from_mesh_object(Object *object)
+static Mesh *mesh_new_from_mesh(Object *object, Mesh *mesh)
 {
-  Mesh *mesh_input = object->data;
-  /* If we are in edit mode, use evaluated mesh from edit structure, matching to what
-   * viewport is using for visualization. */
-  if (mesh_input->edit_mesh != NULL && mesh_input->edit_mesh->mesh_eval_final) {
-    mesh_input = mesh_input->edit_mesh->mesh_eval_final;
-  }
   Mesh *mesh_result = NULL;
   BKE_id_copy_ex(NULL,
-                 &mesh_input->id,
+                 &mesh->id,
                  (ID **)&mesh_result,
                  LIB_ID_CREATE_NO_MAIN | LIB_ID_CREATE_NO_USER_REFCOUNT);
   /* NOTE: Materials should already be copied. */
@@ -1101,7 +1095,52 @@ static Mesh *mesh_new_from_mesh_object(Object *object)
   return mesh_result;
 }
 
-Mesh *BKE_mesh_new_from_object(Object *object)
+static Mesh *mesh_new_from_mesh_object_with_layers(Depsgraph *depsgraph, Object *object)
+{
+  if (DEG_is_original_id(&object->id)) {
+    return mesh_new_from_mesh(object, (Mesh *)object->data);
+  }
+
+  if (depsgraph == NULL) {
+    return NULL;
+  }
+
+  Object object_for_eval = *object;
+  if (object_for_eval.runtime.mesh_orig != NULL) {
+    object_for_eval.data = object_for_eval.runtime.mesh_orig;
+  }
+
+  Scene *scene = DEG_get_evaluated_scene(depsgraph);
+  CustomData_MeshMasks mask = CD_MASK_MESH;
+  Mesh *result;
+
+  if (DEG_get_mode(depsgraph) == DAG_EVAL_RENDER) {
+    result = mesh_create_eval_final_render(depsgraph, scene, &object_for_eval, &mask);
+  }
+  else {
+    result = mesh_create_eval_final_view(depsgraph, scene, &object_for_eval, &mask);
+  }
+
+  return result;
+}
+
+static Mesh *mesh_new_from_mesh_object(Depsgraph *depsgraph,
+                                       Object *object,
+                                       bool preserve_all_data_layers)
+{
+  if (preserve_all_data_layers) {
+    return mesh_new_from_mesh_object_with_layers(depsgraph, object);
+  }
+  Mesh *mesh_input = object->data;
+  /* If we are in edit mode, use evaluated mesh from edit structure, matching to what
+   * viewport is using for visualization. */
+  if (mesh_input->edit_mesh != NULL && mesh_input->edit_mesh->mesh_eval_final) {
+    mesh_input = mesh_input->edit_mesh->mesh_eval_final;
+  }
+  return mesh_new_from_mesh(object, mesh_input);
+}
+
+Mesh *BKE_mesh_new_from_object(Depsgraph *depsgraph, Object *object, bool preserve_all_data_layers)
 {
   Mesh *new_mesh = NULL;
   switch (object->type) {
@@ -1114,7 +1153,7 @@ Mesh *BKE_mesh_new_from_object(Object *object)
       new_mesh = mesh_new_from_mball_object(object);
       break;
     case OB_MESH:
-      new_mesh = mesh_new_from_mesh_object(object);
+      new_mesh = mesh_new_from_mesh_object(depsgraph, object, preserve_all_data_layers);
       break;
     default:
       /* Object does not have geometry data. */
@@ -1144,9 +1183,12 @@ static int foreach_libblock_make_original_and_usercount_callback(void *user_data
   return IDWALK_RET_NOP;
 }
 
-Mesh *BKE_mesh_new_from_object_to_bmain(Main *bmain, Object *object)
+Mesh *BKE_mesh_new_from_object_to_bmain(Main *bmain,
+                                        Depsgraph *depsgraph,
+                                        Object *object,
+                                        bool preserve_all_data_layers)
 {
-  Mesh *mesh = BKE_mesh_new_from_object(object);
+  Mesh *mesh = BKE_mesh_new_from_object(depsgraph, object, preserve_all_data_layers);
 
   /* Make sure mesh only points original datablocks, also increase users of materials and other
    * possibly referenced data-blocks.
diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 85ca9cb26b9..fcb1066b633 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -4499,11 +4499,11 @@ void BKE_object_update_select_id(struct Main *bmain)
   }
 }
 
-Mesh *BKE_object_to_mesh(Object *object)
+Mesh *BKE_object_to_mesh(Depsgraph *depsgraph, Object *object, bool preserve_all_data_layers)
 {
   BKE_object_to_mesh_clear(object);
 
-  Mesh *mesh = BKE_mesh_new_from_object(object);
+  Mesh *mesh = BKE_mesh_new_from_object(depsgraph, object, preserve_all_data_layers);
   object->runtime.object_as_temp_mesh = mesh;
   return mesh;
 }