Refactor: Move mesh face dot tag out of MVert

Continuing the refactors described in T93602, this commit moves
the face dot tag set by the subdivision surface modifier out of
`MVert` to `MeshRuntime`. This clarifies its status as runtime data
and allows further refactoring of mesh positions in the future.

Before, `BKE_modifiers_uses_subsurf_facedots` was used to check
whether subsurf face dots should be drawn, but now we can just check
if the tags exist on the mesh. Modifiers that create new new geometry
or modify topology will already remove the array by clearing mesh
runtime data.

Differential Revision: https://developer.blender.org/D14680

5 files changed, 17 insertions, 44 deletions

diff --git a/source/blender/blenkernel/BKE_modifier.h b/source/blender/blenkernel/BKE_modifier.h
index 41a02545591..881e86ccc54 100644
--- a/source/blender/blenkernel/BKE_modifier.h
+++ b/source/blender/blenkernel/BKE_modifier.h
@@ -491,7 +491,6 @@ struct Object *BKE_modifiers_is_deformed_by_lattice(struct Object *ob);
 struct Object *BKE_modifiers_is_deformed_by_curve(struct Object *ob);
 bool BKE_modifiers_uses_multires(struct Object *ob);
 bool BKE_modifiers_uses_armature(struct Object *ob, struct bArmature *arm);
-bool BKE_modifiers_uses_subsurf_facedots(const struct Scene *scene, struct Object *ob);
 bool BKE_modifiers_is_correctable_deformed(const struct Scene *scene, struct Object *ob);
 void BKE_modifier_free_temporary_data(struct ModifierData *md);
 
diff --git a/source/blender/blenkernel/intern/mesh_iterators.c b/source/blender/blenkernel/intern/mesh_iterators.c
index e164ad9721b..77e62918441 100644
--- a/source/blender/blenkernel/intern/mesh_iterators.c
+++ b/source/blender/blenkernel/intern/mesh_iterators.c
@@ -310,6 +310,8 @@ void BKE_mesh_foreach_mapped_subdiv_face_center(
                                       BKE_mesh_vertex_normals_ensure(mesh) :
                                       NULL;
   const int *index = CustomData_get_layer(&mesh->pdata, CD_ORIGINDEX);
+  const BLI_bitmap *facedot_tags = mesh->runtime.subsurf_face_dot_tags;
+  BLI_assert(facedot_tags != NULL);
 
   if (index) {
     for (int i = 0; i < mesh->totpoly; i++, mp++) {
@@ -320,8 +322,7 @@ void BKE_mesh_foreach_mapped_subdiv_face_center(
       ml = &mesh->mloop[mp->loopstart];
       for (int j = 0; j < mp->totloop; j++, ml++) {
         mv = &mesh->mvert[ml->v];
-        if (mv->flag & ME_VERT_FACEDOT) {
-
+        if (BLI_BITMAP_TEST(facedot_tags, ml->v)) {
           func(userData,
                orig,
                mv->co,
@@ -335,7 +336,7 @@ void BKE_mesh_foreach_mapped_subdiv_face_center(
       ml = &mesh->mloop[mp->loopstart];
       for (int j = 0; j < mp->totloop; j++, ml++) {
         mv = &mesh->mvert[ml->v];
-        if (mv->flag & ME_VERT_FACEDOT) {
+        if (BLI_BITMAP_TEST(facedot_tags, ml->v)) {
           func(userData, i, mv->co, (flag & MESH_FOREACH_USE_NORMAL) ? vert_normals[ml->v] : NULL);
         }
       }
diff --git a/source/blender/blenkernel/intern/mesh_runtime.cc b/source/blender/blenkernel/intern/mesh_runtime.cc
index b06e867cf37..90e9a2a2ff6 100644
--- a/source/blender/blenkernel/intern/mesh_runtime.cc
+++ b/source/blender/blenkernel/intern/mesh_runtime.cc
@@ -86,6 +86,7 @@ void BKE_mesh_runtime_reset_on_copy(Mesh *mesh, const int UNUSED(flag))
   runtime->looptris = blender::dna::shallow_zero_initialize();
   runtime->bvh_cache = nullptr;
   runtime->shrinkwrap_data = nullptr;
+  runtime->subsurf_face_dot_tags = nullptr;
 
   runtime->vert_normals_dirty = true;
   runtime->poly_normals_dirty = true;
@@ -254,6 +255,8 @@ void BKE_mesh_runtime_clear_geometry(Mesh *mesh)
     mesh->runtime.subdiv_ccg = nullptr;
   }
   BKE_shrinkwrap_discard_boundary_data(mesh);
+
+  MEM_SAFE_FREE(mesh->runtime.subsurf_face_dot_tags);
 }
 
 /** \} */
diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index 395deeda4ad..f4703b32582 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -845,41 +845,6 @@ bool BKE_modifiers_uses_armature(Object *ob, bArmature *arm)
   return false;
 }
 
-bool BKE_modifiers_uses_subsurf_facedots(const struct Scene *scene, Object *ob)
-{
-  /* Search (backward) in the modifier stack to find if we have a subsurf modifier (enabled) before
-   * the last modifier displayed on cage (or if the subsurf is the last). */
-  VirtualModifierData virtualModifierData;
-  ModifierData *md = BKE_modifiers_get_virtual_modifierlist(ob, &virtualModifierData);
-  int cage_index = BKE_modifiers_get_cage_index(scene, ob, NULL, 1);
-  if (cage_index == -1) {
-    return false;
-  }
-  /* Find first modifier enabled on cage. */
-  for (int i = 0; md && i < cage_index; i++) {
-    md = md->next;
-  }
-  /* Now from this point, search for subsurf modifier. */
-  for (; md; md = md->prev) {
-    const ModifierTypeInfo *mti = BKE_modifier_get_info(md->type);
-    if (md->type == eModifierType_Subsurf) {
-      ModifierMode mode = eModifierMode_Realtime | eModifierMode_Editmode;
-      if (BKE_modifier_is_enabled(scene, md, mode)) {
-        return true;
-      }
-    }
-    else if (mti->type == eModifierTypeType_OnlyDeform) {
-      /* These modifiers do not reset the subdiv flag nor change the topology.
-       * We can still search for a subsurf modifier. */
-    }
-    else {
-      /* Other modifiers may reset the subdiv facedot flag or create. */
-      return false;
-    }
-  }
-  return false;
-}
-
 bool BKE_modifier_is_correctable_deformed(ModifierData *md)
 {
   const ModifierTypeInfo *mti = BKE_modifier_get_info(md->type);
diff --git a/source/blender/blenkernel/intern/subdiv_mesh.c b/source/blender/blenkernel/intern/subdiv_mesh.c
index 38239e7ddd6..83e4336e3b1 100644
--- a/source/blender/blenkernel/intern/subdiv_mesh.c
+++ b/source/blender/blenkernel/intern/subdiv_mesh.c
@@ -15,6 +15,7 @@
 #include "DNA_meshdata_types.h"
 
 #include "BLI_alloca.h"
+#include "BLI_bitmap.h"
 #include "BLI_math_vector.h"
 
 #include "BKE_customdata.h"
@@ -464,6 +465,9 @@ static bool subdiv_mesh_topology_info(const SubdivForeachContext *foreach_contex
       subdiv_context->coarse_mesh, num_vertices, num_edges, 0, num_loops, num_polygons, mask);
   subdiv_mesh_ctx_cache_custom_data_layers(subdiv_context);
   subdiv_mesh_prepare_accumulator(subdiv_context, num_vertices);
+  MEM_SAFE_FREE(subdiv_context->subdiv_mesh->runtime.subsurf_face_dot_tags);
+  subdiv_context->subdiv_mesh->runtime.subsurf_face_dot_tags = BLI_BITMAP_NEW(num_vertices,
+                                                                              __func__);
   return true;
 }
 
@@ -527,7 +531,7 @@ static void evaluate_vertex_and_apply_displacement_copy(const SubdivMeshContext
   /* Apply displacement. */
   add_v3_v3(subdiv_vert->co, D);
   /* Remove facedot flag. This can happen if there is more than one subsurf modifier. */
-  subdiv_vert->flag &= ~ME_VERT_FACEDOT;
+  BLI_BITMAP_DISABLE(ctx->subdiv_mesh->runtime.subsurf_face_dot_tags, subdiv_vertex_index);
 }
 
 static void evaluate_vertex_and_apply_displacement_interpolate(
@@ -687,12 +691,13 @@ static bool subdiv_mesh_is_center_vertex(const MPoly *coarse_poly, const float u
 }
 
 static void subdiv_mesh_tag_center_vertex(const MPoly *coarse_poly,
-                                          MVert *subdiv_vert,
+                                          const int subdiv_vertex_index,
                                           const float u,
-                                          const float v)
+                                          const float v,
+                                          Mesh *subdiv_mesh)
 {
   if (subdiv_mesh_is_center_vertex(coarse_poly, u, v)) {
-    subdiv_vert->flag |= ME_VERT_FACEDOT;
+    BLI_BITMAP_ENABLE(subdiv_mesh->runtime.subsurf_face_dot_tags, subdiv_vertex_index);
   }
 }
 
@@ -717,7 +722,7 @@ static void subdiv_mesh_vertex_inner(const SubdivForeachContext *foreach_context
   subdiv_mesh_ensure_vertex_interpolation(ctx, tls, coarse_poly, coarse_corner);
   subdiv_vertex_data_interpolate(ctx, subdiv_vert, &tls->vertex_interpolation, u, v);
   BKE_subdiv_eval_final_point(subdiv, ptex_face_index, u, v, subdiv_vert->co);
-  subdiv_mesh_tag_center_vertex(coarse_poly, subdiv_vert, u, v);
+  subdiv_mesh_tag_center_vertex(coarse_poly, subdiv_vertex_index, u, v, subdiv_mesh);
 }
 
 /** \} */