Subdiv: Split evaluation begin+refine into separate steps

Actually, begin will do the entire initialization.

Refine will only refine if there is a topology refiner associated
with the Subdiv descriptor.

Allows to refine Subdiv to new coarse positions without touching
displacement evaluation. Will be needed to update SubdivCCG during
sculpt undo.

source/blender/blenkernel/BKE_subdiv_eval.h

@@ -38,7 +38,10 @@ bool BKE_subdiv_eval_begin(struct Subdiv *subdiv);
 
 /* coarse_vertex_cos is an optional argument which allows to override coordinates of the coarse
  * mesh. */
-bool BKE_subdiv_eval_update_from_mesh(struct Subdiv *subdiv,
+bool BKE_subdiv_eval_begin_from_mesh(struct Subdiv *subdiv,
+                                     const struct Mesh *mesh,
+                                     const float (*coarse_vertex_cos)[3]);
+bool BKE_subdiv_eval_refine_from_mesh(struct Subdiv *subdiv,
                                       const struct Mesh *mesh,
                                       const float (*coarse_vertex_cos)[3]);
 

source/blender/blenkernel/intern/multires_reshape_apply_base.c

@@ -177,7 +177,7 @@ void multires_reshape_apply_base_refit_base_mesh(MultiresReshapeContext *reshape
 
 void multires_reshape_apply_base_refine_from_base(MultiresReshapeContext *reshape_context)
 {
-  BKE_subdiv_eval_update_from_mesh(reshape_context->subdiv, reshape_context->base_mesh, NULL);
+  BKE_subdiv_eval_refine_from_mesh(reshape_context->subdiv, reshape_context->base_mesh, NULL);
 }
 
 void multires_reshape_apply_base_refine_from_deform(MultiresReshapeContext *reshape_context)
@@ -192,7 +192,7 @@ void multires_reshape_apply_base_refine_from_deform(MultiresReshapeContext *resh
   float(*deformed_verts)[3] = BKE_multires_create_deformed_base_mesh_vert_coords(
       depsgraph, object, mmd, NULL);
 
-  BKE_subdiv_eval_update_from_mesh(
+  BKE_subdiv_eval_refine_from_mesh(
       reshape_context->subdiv, reshape_context->base_mesh, deformed_verts);
 
   MEM_freeN(deformed_verts);

source/blender/blenkernel/intern/multires_reshape_util.c

@@ -67,7 +67,7 @@ Subdiv *multires_reshape_create_subdiv(Depsgraph *depsgraph,
   SubdivSettings subdiv_settings;
   BKE_multires_subdiv_settings_init(&subdiv_settings, mmd);
   Subdiv *subdiv = BKE_subdiv_new_from_mesh(&subdiv_settings, base_mesh);
-  if (!BKE_subdiv_eval_update_from_mesh(subdiv, base_mesh, NULL)) {
+  if (!BKE_subdiv_eval_begin_from_mesh(subdiv, base_mesh, NULL)) {
     BKE_subdiv_free(subdiv);
     return NULL;
   }

source/blender/blenkernel/intern/subdiv_ccg.c

@@ -589,7 +589,7 @@ Mesh *BKE_subdiv_to_ccg_mesh(Subdiv *subdiv,
 {
   /* Make sure evaluator is ready. */
   BKE_subdiv_stats_begin(&subdiv->stats, SUBDIV_STATS_SUBDIV_TO_CCG);
-  if (!BKE_subdiv_eval_update_from_mesh(subdiv, coarse_mesh, NULL)) {
+  if (!BKE_subdiv_eval_begin_from_mesh(subdiv, coarse_mesh, NULL)) {
     if (coarse_mesh->totpoly) {
       return NULL;
     }

source/blender/blenkernel/intern/subdiv_deform.c

@@ -194,7 +194,7 @@ void BKE_subdiv_deform_coarse_vertices(struct Subdiv *subdiv,
   BKE_subdiv_stats_begin(&subdiv->stats, SUBDIV_STATS_SUBDIV_TO_MESH);
   /* Make sure evaluator is up to date with possible new topology, and that
    * is refined for the new positions of coarse vertices. */
-  if (!BKE_subdiv_eval_update_from_mesh(subdiv, coarse_mesh, vertex_cos)) {
+  if (!BKE_subdiv_eval_begin_from_mesh(subdiv, coarse_mesh, vertex_cos)) {
     /* This could happen in two situations:
      * - OpenSubdiv is disabled.
      * - Something totally bad happened, and OpenSubdiv rejected our

source/blender/blenkernel/intern/subdiv_eval.c

@@ -121,13 +121,20 @@ static void set_face_varying_data_from_uv(Subdiv *subdiv,
   }
 }
 
-bool BKE_subdiv_eval_update_from_mesh(Subdiv *subdiv,
-                                      const Mesh *mesh,
-                                      const float (*coarse_vertex_cos)[3])
+bool BKE_subdiv_eval_begin_from_mesh(Subdiv *subdiv,
+                                     const Mesh *mesh,
+                                     const float (*coarse_vertex_cos)[3])
 {
   if (!BKE_subdiv_eval_begin(subdiv)) {
     return false;
   }
+  return BKE_subdiv_eval_refine_from_mesh(subdiv, mesh, coarse_vertex_cos);
+}
+
+bool BKE_subdiv_eval_refine_from_mesh(Subdiv *subdiv,
+                                      const Mesh *mesh,
+                                      const float (*coarse_vertex_cos)[3])
+{
   if (subdiv->evaluator == NULL) {
     /* NOTE: This situation is supposed to be handled by begin(). */
     BLI_assert(!"Is not supposed to happen");

source/blender/blenkernel/intern/subdiv_mesh.c

@@ -1168,7 +1168,7 @@ Mesh *BKE_subdiv_to_mesh(Subdiv *subdiv,
   BKE_subdiv_stats_begin(&subdiv->stats, SUBDIV_STATS_SUBDIV_TO_MESH);
   /* Make sure evaluator is up to date with possible new topology, and that
    * it is refined for the new positions of coarse vertices. */
-  if (!BKE_subdiv_eval_update_from_mesh(subdiv, coarse_mesh, NULL)) {
+  if (!BKE_subdiv_eval_begin_from_mesh(subdiv, coarse_mesh, NULL)) {
     /* This could happen in two situations:
      * - OpenSubdiv is disabled.
      * - Something totally bad happened, and OpenSubdiv rejected our