Sculpt: New attribute API

New unified attribute API for sculpt code.

= Basic Design =

The sculpt attribute API can create temporary or permanent attributes (only supported in `PBVH_FACES` mode).  Attributes are created via `BKE_sculpt_attribute_ensure.`

Attributes can be explicit CustomData attributes or simple array-based pseudo-attributes (this is useful for PBVH_GRIDS and PBVH_BMESH).

== `SculptAttributePointers` ==

There is a structure in `SculptSession` for convenience attribute pointers, `ss->attrs`.  Standard attributes should assign these; the attribute API will automatically clear them when the associated attributes are released.  For example, the automasking code stores its factor attribute layer in `ss->attrs.automasking_factor`.

== Naming ==

Temporary attributes should use the SCULPT_ATTRIBUTE_NAME macro for naming, it takes an entry in `SculptAttributePointers` and builds a layer name.

== `SculptAttribute` ==

Attributes are referenced by a special `SculptAttribute` structure, which holds
all the info needed to look up elements of an attribute at run time.

All of these structures live in a preallocated flat array in `SculptSession`, `ss->temp_attributes`.  This is extremely important.  Since any change to the `CustomData` layout can in principle invalidate every extant `SculptAttribute`, having them all in one block of memory whose location doesn't change allows us to update them transparently.

This makes for much simpler code and eliminates bugs.  To see why this is tricky to get right, imagine we want to create three attributes in PBVH_BMESH mode and we provide our own `SculptAttribute` structs for the API to fill in.  Each new layer will invalidate the `CustomData` block offsets in the prior one, leading to memory corruption.

Reviewed by: Brecht Van Lommel
Differential Revision: https://developer.blender.org/D15496
Ref D15496

1 files changed, 598 insertions, 9 deletions

diff --git a/source/blender/blenkernel/intern/paint.cc b/source/blender/blenkernel/intern/paint.cc
index ea1bd3c1cc3..22f5b4d54c6 100644
--- a/source/blender/blenkernel/intern/paint.cc
+++ b/source/blender/blenkernel/intern/paint.cc
@@ -25,6 +25,7 @@
 #include "BLI_hash.h"
 #include "BLI_listbase.h"
 #include "BLI_math_vector.h"
+#include "BLI_string_utf8.h"
 #include "BLI_utildefines.h"
 
 #include "BLT_translation.h"
@@ -65,6 +66,16 @@
 
 #include "bmesh.h"
 
+static void sculpt_attribute_update_refs(Object *ob);
+static SculptAttribute *sculpt_attribute_ensure_ex(Object *ob,
+                                                   eAttrDomain domain,
+                                                   eCustomDataType proptype,
+                                                   const char *name,
+                                                   const SculptAttributeParams *params,
+                                                   PBVHType pbvhtype,
+                                                   bool flat_array_for_bmesh);
+void sculptsession_bmesh_add_layers(Object *ob);
+
 using blender::MutableSpan;
 using blender::Span;
 
@@ -1430,13 +1441,9 @@ static void sculptsession_free_pbvh(Object *object)
   MEM_SAFE_FREE(ss->vemap);
   MEM_SAFE_FREE(ss->vemap_mem);
 
-  MEM_SAFE_FREE(ss->persistent_base);
-
   MEM_SAFE_FREE(ss->preview_vert_list);
   ss->preview_vert_count = 0;
 
-  MEM_SAFE_FREE(ss->preview_vert_list);
-
   MEM_SAFE_FREE(ss->vertex_info.connected_component);
   MEM_SAFE_FREE(ss->vertex_info.boundary);
 
@@ -1470,6 +1477,8 @@ void BKE_sculptsession_free(Object *ob)
   if (ob && ob->sculpt) {
     SculptSession *ss = ob->sculpt;
 
+    BKE_sculpt_attribute_destroy_temporary_all(ob);
+
     if (ss->bm) {
       BKE_sculptsession_bm_to_me(ob, true);
       BM_mesh_free(ss->bm);
@@ -1628,6 +1637,21 @@ static bool sculpt_modifiers_active(Scene *scene, Sculpt *sd, Object *ob)
   return false;
 }
 
+/* Helper function to keep persistent base attribute references up to
+ * date.  This is a bit more tricky since they persist across strokes.
+ */
+static void sculpt_update_persistent_base(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+
+  ss->attrs.persistent_co = BKE_sculpt_attribute_get(
+      ob, ATTR_DOMAIN_POINT, CD_PROP_FLOAT3, SCULPT_ATTRIBUTE_NAME(persistent_co));
+  ss->attrs.persistent_no = BKE_sculpt_attribute_get(
+      ob, ATTR_DOMAIN_POINT, CD_PROP_FLOAT3, SCULPT_ATTRIBUTE_NAME(persistent_no));
+  ss->attrs.persistent_disp = BKE_sculpt_attribute_get(
+      ob, ATTR_DOMAIN_POINT, CD_PROP_FLOAT, SCULPT_ATTRIBUTE_NAME(persistent_disp));
+}
+
 static void sculpt_update_object(
     Depsgraph *depsgraph, Object *ob, Object *ob_eval, bool need_pmap, bool is_paint_tool)
 {
@@ -1726,6 +1750,9 @@ static void sculpt_update_object(
 
   BKE_pbvh_face_sets_color_set(ss->pbvh, me->face_sets_color_seed, me->face_sets_color_default);
 
+  sculpt_attribute_update_refs(ob);
+  sculpt_update_persistent_base(ob);
+
   if (need_pmap && ob->type == OB_MESH && !ss->pmap) {
     BKE_mesh_vert_poly_map_create(&ss->pmap,
                                   &ss->pmap_mem,
@@ -2119,13 +2146,16 @@ void BKE_sculpt_sync_face_visibility_to_grids(Mesh *mesh, SubdivCCG *subdiv_ccg)
 
 static PBVH *build_pbvh_for_dynamic_topology(Object *ob)
 {
-  PBVH *pbvh = BKE_pbvh_new();
+  PBVH *pbvh = ob->sculpt->pbvh = BKE_pbvh_new(PBVH_BMESH);
+
+  sculptsession_bmesh_add_layers(ob);
+
   BKE_pbvh_build_bmesh(pbvh,
                        ob->sculpt->bm,
                        ob->sculpt->bm_smooth_shading,
                        ob->sculpt->bm_log,
-                       ob->sculpt->cd_vert_node_offset,
-                       ob->sculpt->cd_face_node_offset);
+                       ob->sculpt->attrs.dyntopo_node_id_vertex->bmesh_cd_offset,
+                       ob->sculpt->attrs.dyntopo_node_id_face->bmesh_cd_offset);
   pbvh_show_mask_set(pbvh, ob->sculpt->show_mask);
   pbvh_show_face_sets_set(pbvh, false);
   return pbvh;
@@ -2135,7 +2165,7 @@ static PBVH *build_pbvh_from_regular_mesh(Object *ob, Mesh *me_eval_deform, bool
 {
   Mesh *me = BKE_object_get_original_mesh(ob);
   const int looptris_num = poly_to_tri_count(me->totpoly, me->totloop);
-  PBVH *pbvh = BKE_pbvh_new();
+  PBVH *pbvh = BKE_pbvh_new(PBVH_FACES);
   BKE_pbvh_respect_hide_set(pbvh, respect_hide);
 
   MutableSpan<MVert> verts = me->verts_for_write();
@@ -2178,7 +2208,7 @@ static PBVH *build_pbvh_from_ccg(Object *ob, SubdivCCG *subdiv_ccg, bool respect
 {
   CCGKey key;
   BKE_subdiv_ccg_key_top_level(&key, subdiv_ccg);
-  PBVH *pbvh = BKE_pbvh_new();
+  PBVH *pbvh = BKE_pbvh_new(PBVH_GRIDS);
   BKE_pbvh_respect_hide_set(pbvh, respect_hide);
 
   Mesh *base_mesh = BKE_mesh_from_object(ob);
@@ -2288,3 +2318,562 @@ void BKE_paint_face_set_overlay_color_get(const int face_set, const int seed, uc
              &rgba[2]);
   rgba_float_to_uchar(r_color, rgba);
 }
+
+int BKE_sculptsession_vertex_count(const SculptSession *ss)
+{
+  switch (BKE_pbvh_type(ss->pbvh)) {
+    case PBVH_FACES:
+      return ss->totvert;
+    case PBVH_BMESH:
+      return BM_mesh_elem_count(ss->bm, BM_VERT);
+    case PBVH_GRIDS:
+      return BKE_pbvh_get_grid_num_verts(ss->pbvh);
+  }
+
+  return 0;
+}
+
+/** Returns pointer to a CustomData associated with a given domain, if
+ * one exists.  If not nullptr is returned (this may happen with e.g.
+ * multires and ATTR_DOMAIN_POINT).
+ */
+static CustomData *sculpt_get_cdata(Object *ob, eAttrDomain domain)
+{
+  SculptSession *ss = ob->sculpt;
+
+  if (ss->bm) {
+    switch (domain) {
+      case ATTR_DOMAIN_POINT:
+        return &ss->bm->vdata;
+      case ATTR_DOMAIN_FACE:
+        return &ss->bm->pdata;
+      default:
+        BLI_assert_unreachable();
+        return NULL;
+    }
+  }
+  else {
+    Mesh *me = BKE_object_get_original_mesh(ob);
+
+    switch (domain) {
+      case ATTR_DOMAIN_POINT:
+        /* Cannot get vertex domain for multires grids. */
+        if (ss->pbvh && BKE_pbvh_type(ss->pbvh) == PBVH_GRIDS) {
+          return nullptr;
+        }
+
+        return &me->vdata;
+      case ATTR_DOMAIN_FACE:
+        return &me->pdata;
+      default:
+        BLI_assert_unreachable();
+        return NULL;
+    }
+  }
+}
+
+static int sculpt_attr_elem_count_get(Object *ob, eAttrDomain domain)
+{
+  SculptSession *ss = ob->sculpt;
+
+  switch (domain) {
+    case ATTR_DOMAIN_POINT:
+      return BKE_sculptsession_vertex_count(ss);
+      break;
+    case ATTR_DOMAIN_FACE:
+      return ss->totfaces;
+      break;
+    default:
+      BLI_assert_unreachable();
+      return 0;
+  }
+}
+
+static bool sculpt_attribute_create(SculptSession *ss,
+                                    Object *ob,
+                                    eAttrDomain domain,
+                                    eCustomDataType proptype,
+                                    const char *name,
+                                    SculptAttribute *out,
+                                    const SculptAttributeParams *params,
+                                    PBVHType pbvhtype,
+                                    bool flat_array_for_bmesh)
+{
+  Mesh *me = BKE_object_get_original_mesh(ob);
+
+  bool simple_array = params->simple_array;
+  bool permanent = params->permanent;
+
+  out->params = *params;
+  out->proptype = proptype;
+  out->domain = domain;
+  BLI_strncpy_utf8(out->name, name, sizeof(out->name));
+
+  /* Force non-CustomData simple_array mode if not PBVH_FACES. */
+  if (pbvhtype == PBVH_GRIDS || (pbvhtype == PBVH_BMESH && flat_array_for_bmesh)) {
+    if (permanent) {
+      printf(
+          "%s: error: tried to make permanent customdata in multires or bmesh mode; will make "
+          "local "
+          "array "
+          "instead.\n",
+          __func__);
+      permanent = out->params.permanent = false;
+    }
+
+    simple_array = out->params.simple_array = true;
+  }
+
+  BLI_assert(!(simple_array && permanent));
+
+  int totelem = sculpt_attr_elem_count_get(ob, domain);
+
+  if (simple_array) {
+    int elemsize = CustomData_sizeof(proptype);
+
+    out->data = MEM_calloc_arrayN(totelem, elemsize, __func__);
+
+    out->data_for_bmesh = ss->bm != NULL;
+    out->bmesh_cd_offset = -1;
+    out->layer = NULL;
+    out->elem_size = elemsize;
+    out->used = true;
+    out->elem_num = totelem;
+
+    return true;
+  }
+
+  switch (BKE_pbvh_type(ss->pbvh)) {
+    case PBVH_BMESH: {
+      CustomData *cdata = NULL;
+      out->data_for_bmesh = true;
+
+      switch (domain) {
+        case ATTR_DOMAIN_POINT:
+          cdata = &ss->bm->vdata;
+          break;
+        case ATTR_DOMAIN_FACE:
+          cdata = &ss->bm->pdata;
+          break;
+        default:
+          out->used = false;
+          return false;
+      }
+
+      BLI_assert(CustomData_get_named_layer_index(cdata, proptype, name) == -1);
+
+      BM_data_layer_add_named(ss->bm, cdata, proptype, name);
+      int index = CustomData_get_named_layer_index(cdata, proptype, name);
+
+      if (!permanent) {
+        cdata->layers[index].flag |= CD_FLAG_TEMPORARY | CD_FLAG_NOCOPY;
+      }
+
+      out->data = NULL;
+      out->layer = cdata->layers + index;
+      out->bmesh_cd_offset = out->layer->offset;
+      out->elem_size = CustomData_sizeof(proptype);
+      break;
+    }
+    case PBVH_FACES: {
+      CustomData *cdata = NULL;
+
+      out->data_for_bmesh = false;
+
+      switch (domain) {
+        case ATTR_DOMAIN_POINT:
+          cdata = &me->vdata;
+          break;
+        case ATTR_DOMAIN_FACE:
+          cdata = &me->pdata;
+          break;
+        default:
+          out->used = false;
+          return false;
+      }
+
+      BLI_assert(CustomData_get_named_layer_index(cdata, proptype, name) == -1);
+
+      CustomData_add_layer_named(cdata, proptype, CD_SET_DEFAULT, NULL, totelem, name);
+      int index = CustomData_get_named_layer_index(cdata, proptype, name);
+
+      if (!permanent) {
+        cdata->layers[index].flag |= CD_FLAG_TEMPORARY | CD_FLAG_NOCOPY;
+      }
+
+      out->data = NULL;
+      out->layer = cdata->layers + index;
+      out->bmesh_cd_offset = -1;
+      out->data = out->layer->data;
+      out->elem_size = CustomData_get_elem_size(out->layer);
+
+      break;
+    }
+    case PBVH_GRIDS: {
+      /* GRIDS should have been handled as simple arrays. */
+      BLI_assert_unreachable();
+      break;
+    }
+    default:
+      BLI_assert_unreachable();
+      break;
+  }
+
+  out->used = true;
+  out->elem_num = totelem;
+
+  return true;
+}
+
+static bool sculpt_attr_update(Object *ob, SculptAttribute *attr)
+{
+  SculptSession *ss = ob->sculpt;
+  int elem_num = sculpt_attr_elem_count_get(ob, attr->domain);
+
+  bool bad = false;
+
+  if (attr->params.simple_array) {
+    bad = attr->elem_num != elem_num;
+
+    if (bad) {
+      MEM_SAFE_FREE(attr->data);
+    }
+  }
+  else {
+    CustomData *cdata = sculpt_get_cdata(ob, attr->domain);
+
+    if (cdata) {
+      int layer_index = CustomData_get_named_layer_index(cdata, attr->proptype, attr->name);
+
+      if (layer_index != -1 && attr->data_for_bmesh) {
+        attr->bmesh_cd_offset = cdata->layers[layer_index].offset;
+      }
+      else {
+        bad = true;
+      }
+    }
+  }
+
+  if (bad) {
+    sculpt_attribute_create(ss,
+                            ob,
+                            attr->domain,
+                            attr->proptype,
+                            attr->name,
+                            attr,
+                            &attr->params,
+                            BKE_pbvh_type(ss->pbvh),
+                            true);
+  }
+
+  return bad;
+}
+
+static SculptAttribute *sculpt_get_cached_layer(SculptSession *ss,
+                                                eAttrDomain domain,
+                                                eCustomDataType proptype,
+                                                const char *name)
+{
+  for (int i = 0; i < SCULPT_MAX_ATTRIBUTES; i++) {
+    SculptAttribute *attr = ss->temp_attributes + i;
+
+    if (attr->used && STREQ(attr->name, name) && attr->proptype == proptype &&
+        attr->domain == domain) {
+
+      return attr;
+    }
+  }
+
+  return NULL;
+}
+
+bool BKE_sculpt_attribute_exists(Object *ob,
+                                 eAttrDomain domain,
+                                 eCustomDataType proptype,
+                                 const char *name)
+{
+  SculptSession *ss = ob->sculpt;
+  SculptAttribute *attr = sculpt_get_cached_layer(ss, domain, proptype, name);
+
+  if (attr) {
+    return true;
+  }
+
+  CustomData *cdata = sculpt_get_cdata(ob, domain);
+  return CustomData_get_named_layer_index(cdata, proptype, name) != -1;
+
+  return false;
+}
+
+static SculptAttribute *sculpt_alloc_attr(SculptSession *ss)
+{
+  for (int i = 0; i < SCULPT_MAX_ATTRIBUTES; i++) {
+    if (!ss->temp_attributes[i].used) {
+      memset((void *)(ss->temp_attributes + i), 0, sizeof(SculptAttribute));
+      ss->temp_attributes[i].used = true;
+
+      return ss->temp_attributes + i;
+    }
+  }
+
+  BLI_assert_unreachable();
+  return NULL;
+}
+
+SculptAttribute *BKE_sculpt_attribute_get(struct Object *ob,
+                                          eAttrDomain domain,
+                                          eCustomDataType proptype,
+                                          const char *name)
+{
+  SculptSession *ss = ob->sculpt;
+
+  /* See if attribute is cached in ss->temp_attributes. */
+  SculptAttribute *attr = sculpt_get_cached_layer(ss, domain, proptype, name);
+
+  if (attr) {
+    sculpt_attr_update(ob, attr);
+    return attr;
+  }
+
+  /* Does attribute exist in CustomData layout? */
+  CustomData *cdata = sculpt_get_cdata(ob, domain);
+  if (cdata) {
+    int index = CustomData_get_named_layer_index(cdata, proptype, name);
+
+    if (index != -1) {
+      int totelem = 0;
+
+      switch (domain) {
+        case ATTR_DOMAIN_POINT:
+          totelem = BKE_sculptsession_vertex_count(ss);
+          break;
+        case ATTR_DOMAIN_FACE:
+          totelem = ss->totfaces;
+          break;
+        default:
+          BLI_assert_unreachable();
+          break;
+      }
+
+      attr = sculpt_alloc_attr(ss);
+
+      attr->used = true;
+      attr->proptype = proptype;
+      attr->data = cdata->layers[index].data;
+      attr->bmesh_cd_offset = cdata->layers[index].offset;
+      attr->elem_num = totelem;
+      attr->layer = cdata->layers + index;
+      attr->elem_size = CustomData_get_elem_size(attr->layer);
+
+      BLI_strncpy_utf8(attr->name, name, sizeof(attr->name));
+      return attr;
+    }
+  }
+
+  return NULL;
+}
+
+static SculptAttribute *sculpt_attribute_ensure_ex(Object *ob,
+                                                   eAttrDomain domain,
+                                                   eCustomDataType proptype,
+                                                   const char *name,
+                                                   const SculptAttributeParams *params,
+                                                   PBVHType pbvhtype,
+                                                   bool flat_array_for_bmesh)
+{
+  SculptSession *ss = ob->sculpt;
+  SculptAttribute *attr = BKE_sculpt_attribute_get(ob, domain, proptype, name);
+
+  if (attr) {
+    return attr;
+  }
+
+  attr = sculpt_alloc_attr(ss);
+
+  /* Create attribute. */
+  sculpt_attribute_create(
+      ss, ob, domain, proptype, name, attr, params, pbvhtype, flat_array_for_bmesh);
+  sculpt_attribute_update_refs(ob);
+
+  return attr;
+}
+
+SculptAttribute *BKE_sculpt_attribute_ensure(Object *ob,
+                                             eAttrDomain domain,
+                                             eCustomDataType proptype,
+                                             const char *name,
+                                             const SculptAttributeParams *params)
+{
+  SculptAttributeParams temp_params = *params;
+
+  return sculpt_attribute_ensure_ex(
+      ob, domain, proptype, name, &temp_params, BKE_pbvh_type(ob->sculpt->pbvh), true);
+}
+
+static void sculptsession_bmesh_attr_update_internal(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+
+  sculptsession_bmesh_add_layers(ob);
+
+  if (ss->pbvh) {
+    BKE_pbvh_update_bmesh_offsets(ss->pbvh,
+                                  ob->sculpt->attrs.dyntopo_node_id_vertex->bmesh_cd_offset,
+                                  ob->sculpt->attrs.dyntopo_node_id_face->bmesh_cd_offset);
+  }
+}
+
+void sculptsession_bmesh_add_layers(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+  SculptAttributeParams params = {0};
+
+  ss->attrs.dyntopo_node_id_vertex = sculpt_attribute_ensure_ex(
+      ob,
+      ATTR_DOMAIN_POINT,
+      CD_PROP_INT32,
+      SCULPT_ATTRIBUTE_NAME(dyntopo_node_id_vertex),
+      &params,
+      PBVH_BMESH,
+      false);
+
+  ss->attrs.dyntopo_node_id_face = sculpt_attribute_ensure_ex(
+      ob,
+      ATTR_DOMAIN_FACE,
+      CD_PROP_INT32,
+      SCULPT_ATTRIBUTE_NAME(dyntopo_node_id_face),
+      &params,
+      PBVH_BMESH,
+      false);
+}
+
+void BKE_sculpt_attributes_destroy_temporary_stroke(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+
+  for (int i = 0; i < SCULPT_MAX_ATTRIBUTES; i++) {
+    SculptAttribute *attr = ss->temp_attributes + i;
+
+    if (attr->params.stroke_only) {
+      BKE_sculpt_attribute_destroy(ob, attr);
+    }
+  }
+}
+
+static void sculpt_attribute_update_refs(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+
+  /* run twice, in case sculpt_attr_update had to recreate a layer and
+     messed up the bmesh offsets. */
+  for (int i = 0; i < 2; i++) {
+    for (int j = 0; j < SCULPT_MAX_ATTRIBUTES; j++) {
+      SculptAttribute *attr = ss->temp_attributes + j;
+
+      if (attr->used) {
+        sculpt_attr_update(ob, attr);
+      }
+    }
+
+    if (ss->bm) {
+      sculptsession_bmesh_attr_update_internal(ob);
+    }
+  }
+
+  Mesh *me = BKE_object_get_original_mesh(ob);
+
+  if (ss->pbvh) {
+    BKE_pbvh_update_active_vcol(ss->pbvh, me);
+  }
+}
+
+bool BKE_paint_uses_channels(ePaintMode mode)
+{
+  return mode == PAINT_MODE_SCULPT;
+}
+
+void BKE_sculpt_attribute_destroy_temporary_all(Object *ob)
+{
+  SculptSession *ss = ob->sculpt;
+
+  for (int i = 0; i < SCULPT_MAX_ATTRIBUTES; i++) {
+    SculptAttribute *attr = ss->temp_attributes + i;
+
+    if (attr->used && !attr->params.permanent) {
+      BKE_sculpt_attribute_destroy(ob, attr);
+    }
+  }
+}
+
+bool BKE_sculpt_attribute_destroy(Object *ob, SculptAttribute *attr)
+{
+  SculptSession *ss = ob->sculpt;
+  eAttrDomain domain = attr->domain;
+
+  BLI_assert(attr->used);
+
+  /* Remove from convienience pointer struct. */
+  SculptAttribute **ptrs = (SculptAttribute **)&ss->attrs;
+  int ptrs_num = sizeof(ss->attrs) / sizeof(void *);
+
+  for (int i = 0; i < ptrs_num; i++) {
+    if (ptrs[i] == attr) {
+      ptrs[i] = NULL;
+    }
+  }
+
+  /* Remove from internal temp_attributes array. */
+  for (int i = 0; i < SCULPT_MAX_ATTRIBUTES; i++) {
+    SculptAttribute *attr2 = ss->temp_attributes + i;
+
+    if (STREQ(attr2->name, attr->name) && attr2->domain == attr->domain &&
+        attr2->proptype == attr->proptype) {
+
+      attr2->used = false;
+    }
+  }
+
+  Mesh *me = BKE_object_get_original_mesh(ob);
+
+  if (attr->params.simple_array) {
+    MEM_SAFE_FREE(attr->data);
+  }
+  else if (ss->bm) {
+    CustomData *cdata = attr->domain == ATTR_DOMAIN_POINT ? &ss->bm->vdata : &ss->bm->pdata;
+
+    BM_data_layer_free_named(ss->bm, cdata, attr->name);
+  }
+  else {
+    CustomData *cdata = NULL;
+    int totelem = 0;
+
+    switch (domain) {
+      case ATTR_DOMAIN_POINT:
+        cdata = ss->bm ? &ss->bm->vdata : &me->vdata;
+        totelem = ss->totvert;
+        break;
+      case ATTR_DOMAIN_FACE:
+        cdata = ss->bm ? &ss->bm->pdata : &me->pdata;
+        totelem = ss->totfaces;
+        break;
+      default:
+        BLI_assert_unreachable();
+        return false;
+    }
+
+    /* We may have been called after destroying ss->bm in which case attr->layer
+     * might be invalid.
+     */
+    int layer_i = CustomData_get_named_layer_index(cdata, attr->proptype, attr->name);
+    if (layer_i != 0) {
+      CustomData_free_layer(cdata, attr->proptype, totelem, layer_i);
+    }
+
+    sculpt_attribute_update_refs(ob);
+  }
+
+  attr->data = NULL;
+  attr->used = false;
+
+  return true;
+}