Fix T94635: Sculpt Smooth in Surface mode with Anchored Stroke crash

Sculpt Smooth in Surface mode (as opposed to Laplacian) needs a cache
initialized on first time. In anchored stroke mode with spherical falloff
this was skipped though (because this starts of with no PBVH nodes and
an early return checks for this) and `first_time` was set to false before
cache initialization.

Now move the cache initalization to happen earlier (same as the cache
initialization for automasking).

Maniphest Tasks: T94635

Differential Revision: https://developer.blender.org/D13746

2 files changed, 10 insertions, 9 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 21bbc9fb543..02886643cb4 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -3238,14 +3238,22 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush, UnifiedPaintSe
     }
   }
 
-  /* Initialize auto-masking cache. For anchored brushes with spherical falloff,
-   * we start off with zero radius, thus we have no PBVH nodes on the first brush step. */
+  /* For anchored brushes with spherical falloff, we start off with zero radius, thus we have no
+   * PBVH nodes on the first brush step. */
   if (totnode ||
       ((brush->falloff_shape == PAINT_FALLOFF_SHAPE_SPHERE) && (brush->flag & BRUSH_ANCHORED))) {
     if (SCULPT_stroke_is_first_brush_step(ss->cache)) {
+      /* Initialize auto-masking cache. */
       if (SCULPT_is_automasking_enabled(sd, ss, brush)) {
         ss->cache->automasking = SCULPT_automasking_cache_init(sd, brush, ob);
       }
+      /* Initialize surface smooth cache. */
+      if ((brush->sculpt_tool == SCULPT_TOOL_SMOOTH) &&
+          (brush->smooth_deform_type == BRUSH_SMOOTH_DEFORM_SURFACE)) {
+        BLI_assert(ss->cache->surface_smooth_laplacian_disp == NULL);
+        ss->cache->surface_smooth_laplacian_disp = MEM_callocN(
+            sizeof(float[3]) * SCULPT_vertex_count_get(ss), "HC smooth laplacian b");
+      }
     }
   }
 
diff --git a/source/blender/editors/sculpt_paint/sculpt_smooth.c b/source/blender/editors/sculpt_paint/sculpt_smooth.c
index 847f42fe9e8..c65489548b7 100644
--- a/source/blender/editors/sculpt_paint/sculpt_smooth.c
+++ b/source/blender/editors/sculpt_paint/sculpt_smooth.c
@@ -538,13 +538,6 @@ static void SCULPT_do_surface_smooth_brush_displace_task_cb_ex(
 void SCULPT_do_surface_smooth_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
 {
   Brush *brush = BKE_paint_brush(&sd->paint);
-  SculptSession *ss = ob->sculpt;
-
-  if (SCULPT_stroke_is_first_brush_step(ss->cache)) {
-    BLI_assert(ss->cache->surface_smooth_laplacian_disp == NULL);
-    ss->cache->surface_smooth_laplacian_disp = MEM_callocN(
-        sizeof(float[3]) * SCULPT_vertex_count_get(ss), "HC smooth laplacian b");
-  }
 
   /* Threaded loop over nodes. */
   SculptThreadedTaskData data = {