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

13 files changed, 42 insertions, 65 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);
 }
 
 /** \} */
diff --git a/source/blender/draw/intern/draw_cache_impl_mesh.c b/source/blender/draw/intern/draw_cache_impl_mesh.c
index ec33d2b5361..c4fa60ef51d 100644
--- a/source/blender/draw/intern/draw_cache_impl_mesh.c
+++ b/source/blender/draw/intern/draw_cache_impl_mesh.c
@@ -2121,7 +2121,7 @@ void DRW_mesh_batch_cache_create_requested(struct TaskGraph *task_graph,
 
   MDEPS_ASSERT_MAP_INDEX(TRIS_PER_MAT_INDEX);
 
-  const bool use_subsurf_fdots = scene ? BKE_modifiers_uses_subsurf_facedots(scene, ob) : false;
+  const bool use_subsurf_fdots = me->runtime.subsurf_face_dot_tags != NULL;
 
   if (do_uvcage) {
     mesh_buffer_cache_create_requested(task_graph,
diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_edituv.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_edituv.cc
index 27149a80f9b..43aa52f08c8 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_edituv.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_edituv.cc
@@ -5,9 +5,7 @@
  * \ingroup draw
  */
 
-#include "BLI_vector.hh"
-
-#include "MEM_guardedalloc.h"
+#include "BLI_bitmap.h"
 
 #include "extract_mesh.h"
 
@@ -538,7 +536,8 @@ static void extract_edituv_fdots_iter_poly_mesh(const MeshRenderData *mr,
 {
   MeshExtract_EditUvElem_Data *data = static_cast<MeshExtract_EditUvElem_Data *>(_data);
   if (mr->use_subsurf_fdots) {
-    /* Check #ME_VERT_FACEDOT. */
+    const BLI_bitmap *facedot_tags = mr->me->runtime.subsurf_face_dot_tags;
+
     const MLoop *mloop = mr->mloop;
     const int ml_index_end = mp->loopstart + mp->totloop;
     for (int ml_index = mp->loopstart; ml_index < ml_index_end; ml_index += 1) {
@@ -546,8 +545,7 @@ static void extract_edituv_fdots_iter_poly_mesh(const MeshRenderData *mr,
 
       const bool real_fdot = (mr->extract_type == MR_EXTRACT_MAPPED && mr->p_origindex &&
                               mr->p_origindex[mp_index] != ORIGINDEX_NONE);
-      const bool subd_fdot = (!mr->use_subsurf_fdots ||
-                              (mr->mvert[ml->v].flag & ME_VERT_FACEDOT) != 0);
+      const bool subd_fdot = BLI_BITMAP_TEST(facedot_tags, ml->v);
       edituv_facedot_add(data,
                          ((mp->flag & ME_HIDE) != 0) || !real_fdot || !subd_fdot,
                          (mp->flag & ME_FACE_SEL) != 0,
diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_fdots.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_fdots.cc
index 8db1660b9d0..4bf732caf0a 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_fdots.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_fdots.cc
@@ -5,9 +5,7 @@
  * \ingroup draw
  */
 
-#include "BLI_vector.hh"
-
-#include "MEM_guardedalloc.h"
+#include "BLI_bitmap.h"
 
 #include "extract_mesh.h"
 
@@ -46,13 +44,13 @@ static void extract_fdots_iter_poly_mesh(const MeshRenderData *mr,
 {
   GPUIndexBufBuilder *elb = static_cast<GPUIndexBufBuilder *>(_userdata);
   if (mr->use_subsurf_fdots) {
-    /* Check #ME_VERT_FACEDOT. */
+    const BLI_bitmap *facedot_tags = mr->me->runtime.subsurf_face_dot_tags;
+
     const MLoop *mloop = mr->mloop;
     const int ml_index_end = mp->loopstart + mp->totloop;
     for (int ml_index = mp->loopstart; ml_index < ml_index_end; ml_index += 1) {
       const MLoop *ml = &mloop[ml_index];
-      const MVert *mv = &mr->mvert[ml->v];
-      if ((mv->flag & ME_VERT_FACEDOT) && !(mr->use_hide && (mp->flag & ME_HIDE))) {
+      if (BLI_BITMAP_TEST(facedot_tags, ml->v) && !(mr->use_hide && (mp->flag & ME_HIDE))) {
         GPU_indexbuf_set_point_vert(elb, mp_index, mp_index);
         return;
       }
diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_pos.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_pos.cc
index 0a34cfa012d..c2b4d389b7c 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_pos.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_pos.cc
@@ -5,6 +5,8 @@
  * \ingroup draw
  */
 
+#include "BLI_bitmap.h"
+
 #include "extract_mesh.h"
 
 #include "draw_subdivision.h"
@@ -75,14 +77,14 @@ static void extract_fdots_pos_iter_poly_mesh(const MeshRenderData *mr,
 
   const MVert *mvert = mr->mvert;
   const MLoop *mloop = mr->mloop;
+  const BLI_bitmap *facedot_tags = mr->me->runtime.subsurf_face_dot_tags;
 
   const int ml_index_end = mp->loopstart + mp->totloop;
   for (int ml_index = mp->loopstart; ml_index < ml_index_end; ml_index += 1) {
     const MLoop *ml = &mloop[ml_index];
     if (mr->use_subsurf_fdots) {
-      const MVert *mv = &mr->mvert[ml->v];
-      if (mv->flag & ME_VERT_FACEDOT) {
-        copy_v3_v3(center[mp_index], mv->co);
+      if (BLI_BITMAP_TEST(facedot_tags, ml->v)) {
+        copy_v3_v3(center[mp_index], mvert[ml->v].co);
         break;
       }
     }
diff --git a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_uv.cc b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_uv.cc
index 7a3c108b75a..26f0b07f676 100644
--- a/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_uv.cc
+++ b/source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_uv.cc
@@ -5,6 +5,8 @@
  * \ingroup draw
  */
 
+#include "BLI_bitmap.h"
+
 #include "extract_mesh.h"
 
 namespace blender::draw {
@@ -72,13 +74,14 @@ static void extract_fdots_uv_iter_poly_mesh(const MeshRenderData *mr,
                                             void *_data)
 {
   MeshExtract_FdotUV_Data *data = static_cast<MeshExtract_FdotUV_Data *>(_data);
+  const BLI_bitmap *facedot_tags = mr->me->runtime.subsurf_face_dot_tags;
+
   const MLoop *mloop = mr->mloop;
   const int ml_index_end = mp->loopstart + mp->totloop;
   for (int ml_index = mp->loopstart; ml_index < ml_index_end; ml_index += 1) {
     const MLoop *ml = &mloop[ml_index];
     if (mr->use_subsurf_fdots) {
-      const MVert *mv = &mr->mvert[ml->v];
-      if (mv->flag & ME_VERT_FACEDOT) {
+      if (BLI_BITMAP_TEST(facedot_tags, ml->v)) {
         copy_v2_v2(data->vbo_data[mp_index], data->uv_data[ml_index].uv);
       }
     }
diff --git a/source/blender/editors/space_view3d/view3d_iterators.c b/source/blender/editors/space_view3d/view3d_iterators.c
index 055aac041f1..4606908b91f 100644
--- a/source/blender/editors/space_view3d/view3d_iterators.c
+++ b/source/blender/editors/space_view3d/view3d_iterators.c
@@ -568,7 +568,7 @@ void mesh_foreachScreenFace(
 
   BM_mesh_elem_table_ensure(vc->em->bm, BM_FACE);
 
-  if (BKE_modifiers_uses_subsurf_facedots(vc->scene, vc->obedit)) {
+  if (me->runtime.subsurf_face_dot_tags != NULL) {
     BKE_mesh_foreach_mapped_subdiv_face_center(
         me, mesh_foreachScreenFace__mapFunc, &data, MESH_FOREACH_NOP);
   }
diff --git a/source/blender/makesdna/DNA_mesh_types.h b/source/blender/makesdna/DNA_mesh_types.h
index 0ff9ebb2337..2b4858d4106 100644
--- a/source/blender/makesdna/DNA_mesh_types.h
+++ b/source/blender/makesdna/DNA_mesh_types.h
@@ -138,7 +138,11 @@ typedef struct Mesh_Runtime {
   float (*vert_normals)[3];
   float (*poly_normals)[3];
 
-  void *_pad2;
+  /**
+   * A #BLI_bitmap containing tags for the center vertices of subdivided polygons, set by the
+   * subdivision surface modifier and used by drawing code instead of polygon center face dots.
+   */
+  uint32_t *subsurf_face_dot_tags;
 } Mesh_Runtime;
 
 typedef struct Mesh {
diff --git a/source/blender/makesdna/DNA_meshdata_types.h b/source/blender/makesdna/DNA_meshdata_types.h
index 3c734419bfe..2a4234bde6a 100644
--- a/source/blender/makesdna/DNA_meshdata_types.h
+++ b/source/blender/makesdna/DNA_meshdata_types.h
@@ -33,7 +33,6 @@ typedef struct MVert {
 enum {
   /*  SELECT = (1 << 0), */
   ME_HIDE = (1 << 4),
-  ME_VERT_FACEDOT = (1 << 5),
 };
 
 /**