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, 36 insertions, 37 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_automasking.cc b/source/blender/editors/sculpt_paint/sculpt_automasking.cc
index a9fe8cc4b2f..34d7a459c1b 100644
--- a/source/blender/editors/sculpt_paint/sculpt_automasking.cc
+++ b/source/blender/editors/sculpt_paint/sculpt_automasking.cc
@@ -122,13 +122,11 @@ float SCULPT_automasking_factor_get(AutomaskingCache *automasking,
     return 1.0f;
   }
 
-  int index = BKE_pbvh_vertex_to_index(ss->pbvh, vert);
-
   /* If the cache is initialized with valid info, use the cache. This is used when the
    * automasking information can't be computed in real time per vertex and needs to be
    * initialized for the whole mesh when the stroke starts. */
-  if (automasking->factor) {
-    return automasking->factor[index];
+  if (ss->attrs.automasking_factor) {
+    return *(float *)SCULPT_vertex_attr_get(vert, ss->attrs.automasking_factor);
   }
 
   if (automasking->settings.flags & BRUSH_AUTOMASKING_FACE_SETS) {
@@ -158,7 +156,6 @@ void SCULPT_automasking_cache_free(AutomaskingCache *automasking)
     return;
   }
 
-  MEM_SAFE_FREE(automasking->factor);
   MEM_SAFE_FREE(automasking);
 }
 
@@ -176,7 +173,6 @@ static bool sculpt_automasking_is_constrained_by_radius(Brush *br)
 }
 
 struct AutomaskFloodFillData {
-  float *automask_factor;
   float radius;
   bool use_radius;
   float location[3];
@@ -190,29 +186,29 @@ static bool automask_floodfill_cb(SculptSession *ss,
                                   void *userdata)
 {
   AutomaskFloodFillData *data = (AutomaskFloodFillData *)userdata;
-  int from_v_i = BKE_pbvh_vertex_to_index(ss->pbvh, from_v);
-  int to_v_i = BKE_pbvh_vertex_to_index(ss->pbvh, to_v);
 
-  data->automask_factor[to_v_i] = 1.0f;
-  data->automask_factor[from_v_i] = 1.0f;
+  *(float *)SCULPT_vertex_attr_get(to_v, ss->attrs.automasking_factor) = 1.0f;
+  *(float *)SCULPT_vertex_attr_get(from_v, ss->attrs.automasking_factor) = 1.0f;
   return (!data->use_radius ||
           SCULPT_is_vertex_inside_brush_radius_symm(
               SCULPT_vertex_co_get(ss, to_v), data->location, data->radius, data->symm));
 }
 
-static float *SCULPT_topology_automasking_init(Sculpt *sd, Object *ob, float *automask_factor)
+static void SCULPT_topology_automasking_init(Sculpt *sd, Object *ob)
 {
   SculptSession *ss = ob->sculpt;
   Brush *brush = BKE_paint_brush(&sd->paint);
 
   if (BKE_pbvh_type(ss->pbvh) == PBVH_FACES && !ss->pmap) {
     BLI_assert_msg(0, "Topology masking: pmap missing");
-    return nullptr;
+    return;
   }
 
   const int totvert = SCULPT_vertex_count_get(ss);
   for (int i : IndexRange(totvert)) {
-    automask_factor[i] = 0.0f;
+    PBVHVertRef vertex = BKE_pbvh_index_to_vertex(ss->pbvh, i);
+
+    (*(float *)SCULPT_vertex_attr_get(vertex, ss->attrs.automasking_factor)) = 0.0f;
   }
 
   /* Flood fill automask to connected vertices. Limited to vertices inside
@@ -222,9 +218,8 @@ static float *SCULPT_topology_automasking_init(Sculpt *sd, Object *ob, float *au
   const float radius = ss->cache ? ss->cache->radius : FLT_MAX;
   SCULPT_floodfill_add_active(sd, ob, ss, &flood, radius);
 
-  AutomaskFloodFillData fdata = {nullptr};
+  AutomaskFloodFillData fdata = {0};
 
-  fdata.automask_factor = automask_factor;
   fdata.radius = radius;
   fdata.use_radius = ss->cache && sculpt_automasking_is_constrained_by_radius(brush);
   fdata.symm = SCULPT_mesh_symmetry_xyz_get(ob);
@@ -232,22 +227,20 @@ static float *SCULPT_topology_automasking_init(Sculpt *sd, Object *ob, float *au
   copy_v3_v3(fdata.location, SCULPT_active_vertex_co_get(ss));
   SCULPT_floodfill_execute(ss, &flood, automask_floodfill_cb, &fdata);
   SCULPT_floodfill_free(&flood);
-
-  return automask_factor;
 }
 
-static float *sculpt_face_sets_automasking_init(Sculpt *sd, Object *ob, float *automask_factor)
+static void sculpt_face_sets_automasking_init(Sculpt *sd, Object *ob)
 {
   SculptSession *ss = ob->sculpt;
   Brush *brush = BKE_paint_brush(&sd->paint);
 
   if (!SCULPT_is_automasking_enabled(sd, ss, brush)) {
-    return nullptr;
+    return;
   }
 
   if (BKE_pbvh_type(ss->pbvh) == PBVH_FACES && !ss->pmap) {
     BLI_assert_msg(0, "Face Sets automasking: pmap missing");
-    return nullptr;
+    return;
   }
 
   int tot_vert = SCULPT_vertex_count_get(ss);
@@ -256,25 +249,22 @@ static float *sculpt_face_sets_automasking_init(Sculpt *sd, Object *ob, float *a
     PBVHVertRef vertex = BKE_pbvh_index_to_vertex(ss->pbvh, i);
 
     if (!SCULPT_vertex_has_face_set(ss, vertex, active_face_set)) {
-      automask_factor[i] *= 0.0f;
+      *(float *)SCULPT_vertex_attr_get(vertex, ss->attrs.automasking_factor) = 0.0f;
     }
   }
-
-  return automask_factor;
 }
 
 #define EDGE_DISTANCE_INF -1
 
-float *SCULPT_boundary_automasking_init(Object *ob,
-                                        eBoundaryAutomaskMode mode,
-                                        int propagation_steps,
-                                        float *automask_factor)
+void SCULPT_boundary_automasking_init(Object *ob,
+                                      eBoundaryAutomaskMode mode,
+                                      int propagation_steps)
 {
   SculptSession *ss = ob->sculpt;
 
   if (!ss->pmap) {
     BLI_assert_msg(0, "Boundary Edges masking: pmap missing");
-    return nullptr;
+    return;
   }
 
   const int totvert = SCULPT_vertex_count_get(ss);
@@ -316,16 +306,19 @@ float *SCULPT_boundary_automasking_init(Object *ob,
   }
 
   for (int i : IndexRange(totvert)) {
+    PBVHVertRef vertex = BKE_pbvh_index_to_vertex(ss->pbvh, i);
+
     if (edge_distance[i] == EDGE_DISTANCE_INF) {
       continue;
     }
     const float p = 1.0f - ((float)edge_distance[i] / (float)propagation_steps);
     const float edge_boundary_automask = pow2f(p);
-    automask_factor[i] *= (1.0f - edge_boundary_automask);
+
+    *(float *)SCULPT_vertex_attr_get(
+        vertex, ss->attrs.automasking_factor) *= (1.0f - edge_boundary_automask);
   }
 
   MEM_SAFE_FREE(edge_distance);
-  return automask_factor;
 }
 
 static void SCULPT_automasking_cache_settings_update(AutomaskingCache *automasking,
@@ -355,9 +348,16 @@ AutomaskingCache *SCULPT_automasking_cache_init(Sculpt *sd, Brush *brush, Object
     return automasking;
   }
 
-  automasking->factor = (float *)MEM_malloc_arrayN(totvert, sizeof(float), "automask_factor");
+  SculptAttributeParams params = {0};
+  params.stroke_only = true;
+
+  ss->attrs.automasking_factor = BKE_sculpt_attribute_ensure(
+      ob, ATTR_DOMAIN_POINT, CD_PROP_FLOAT, SCULPT_ATTRIBUTE_NAME(automasking_factor), &params);
+
   for (int i : IndexRange(totvert)) {
-    automasking->factor[i] = 1.0f;
+    PBVHVertRef vertex = BKE_pbvh_index_to_vertex(ss->pbvh, i);
+
+    (*(float *)SCULPT_vertex_attr_get(vertex, ss->attrs.automasking_factor)) = 0.0f;
   }
 
   const int boundary_propagation_steps = brush ?
@@ -366,22 +366,21 @@ AutomaskingCache *SCULPT_automasking_cache_init(Sculpt *sd, Brush *brush, Object
 
   if (SCULPT_is_automasking_mode_enabled(sd, brush, BRUSH_AUTOMASKING_TOPOLOGY)) {
     SCULPT_vertex_random_access_ensure(ss);
-    SCULPT_topology_automasking_init(sd, ob, automasking->factor);
+    SCULPT_topology_automasking_init(sd, ob);
   }
   if (SCULPT_is_automasking_mode_enabled(sd, brush, BRUSH_AUTOMASKING_FACE_SETS)) {
     SCULPT_vertex_random_access_ensure(ss);
-    sculpt_face_sets_automasking_init(sd, ob, automasking->factor);
+    sculpt_face_sets_automasking_init(sd, ob);
   }
 
   if (SCULPT_is_automasking_mode_enabled(sd, brush, BRUSH_AUTOMASKING_BOUNDARY_EDGES)) {
     SCULPT_vertex_random_access_ensure(ss);
-    SCULPT_boundary_automasking_init(
-        ob, AUTOMASK_INIT_BOUNDARY_EDGES, boundary_propagation_steps, automasking->factor);
+    SCULPT_boundary_automasking_init(ob, AUTOMASK_INIT_BOUNDARY_EDGES, boundary_propagation_steps);
   }
   if (SCULPT_is_automasking_mode_enabled(sd, brush, BRUSH_AUTOMASKING_BOUNDARY_FACE_SETS)) {
     SCULPT_vertex_random_access_ensure(ss);
     SCULPT_boundary_automasking_init(
-        ob, AUTOMASK_INIT_BOUNDARY_FACE_SETS, boundary_propagation_steps, automasking->factor);
+        ob, AUTOMASK_INIT_BOUNDARY_FACE_SETS, boundary_propagation_steps);
   }
 
   return automasking;