From 527e18043cf48a3fd3f1c46f24f6dd927e1231dc Mon Sep 17 00:00:00 2001
From: Hans Goudey <hans@blender.org>
Date: Tue, 2 Jul 2024 14:01:19 -0400
Subject: [PATCH] Refactor: Subdiv: Add utility to evaluate all limit points in
 a grid

---
 source/blender/blenkernel/BKE_subdiv_ccg.hh     |  4 ++++
 source/blender/blenkernel/intern/subdiv_ccg.cc  | 17 +++++++++++++++++
 .../brushes/multires_displacement_eraser.cc     | 16 ++++------------
 3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/source/blender/blenkernel/BKE_subdiv_ccg.hh b/source/blender/blenkernel/BKE_subdiv_ccg.hh
index e53981de3e2..fab87596873 100644
--- a/source/blender/blenkernel/BKE_subdiv_ccg.hh
+++ b/source/blender/blenkernel/BKE_subdiv_ccg.hh
@@ -258,6 +258,10 @@ inline int BKE_subdiv_ccg_grid_to_face_index(const SubdivCCG &subdiv_ccg, const
 void BKE_subdiv_ccg_eval_limit_point(const SubdivCCG &subdiv_ccg,
                                      const SubdivCCGCoord &coord,
                                      float r_point[3]);
+void BKE_subdiv_ccg_eval_limit_positions(const SubdivCCG &subdiv_ccg,
+                                         const CCGKey &key,
+                                         int grid_index,
+                                         blender::MutableSpan<blender::float3> r_limit_positions);
 
 enum SubdivCCGAdjacencyType {
   SUBDIV_CCG_ADJACENT_NONE,
diff --git a/source/blender/blenkernel/intern/subdiv_ccg.cc b/source/blender/blenkernel/intern/subdiv_ccg.cc
index f3450533a92..799263cd532 100644
--- a/source/blender/blenkernel/intern/subdiv_ccg.cc
+++ b/source/blender/blenkernel/intern/subdiv_ccg.cc
@@ -1709,4 +1709,21 @@ void BKE_subdiv_ccg_eval_limit_point(const SubdivCCG &subdiv_ccg,
   eval_limit_point(subdiv, ptex_face_index, u, v, r_point);
 }
 
+void BKE_subdiv_ccg_eval_limit_positions(const SubdivCCG &subdiv_ccg,
+                                         const CCGKey &key,
+                                         const int grid_index,
+                                         const MutableSpan<float3> r_limit_positions)
+{
+  SubdivCCGCoord coord{};
+  coord.grid_index = grid_index;
+  for (const int y : IndexRange(key.grid_size)) {
+    for (const int x : IndexRange(key.grid_size)) {
+      const int i = CCG_grid_xy_to_index(key.grid_size, x, y);
+      coord.x = x;
+      coord.y = y;
+      BKE_subdiv_ccg_eval_limit_point(subdiv_ccg, coord, r_limit_positions[i]);
+    }
+  }
+}
+
 /** \} */
diff --git a/source/blender/editors/sculpt_paint/brushes/multires_displacement_eraser.cc b/source/blender/editors/sculpt_paint/brushes/multires_displacement_eraser.cc
index f2c190cdf15..15b5995cc99 100644
--- a/source/blender/editors/sculpt_paint/brushes/multires_displacement_eraser.cc
+++ b/source/blender/editors/sculpt_paint/brushes/multires_displacement_eraser.cc
@@ -38,18 +38,10 @@ static BLI_NOINLINE void calc_limit_positions(const SubdivCCG &subdiv_ccg,
                                               const MutableSpan<float3> limit_positions)
 {
   const CCGKey key = BKE_subdiv_ccg_key_top_level(subdiv_ccg);
-  for (const int grid : grids) {
-    const int start = grid * key.grid_area;
-    for (const int y : IndexRange(key.grid_size)) {
-      for (const int x : IndexRange(key.grid_size)) {
-        const int offset = CCG_grid_xy_to_index(key.grid_size, x, y);
-        SubdivCCGCoord coord{};
-        coord.grid_index = grid;
-        coord.x = x;
-        coord.y = y;
-        BKE_subdiv_ccg_eval_limit_point(subdiv_ccg, coord, limit_positions[start + offset]);
-      }
-    }
+  for (const int i : grids.index_range()) {
+    const int start = i * key.grid_area;
+    BKE_subdiv_ccg_eval_limit_positions(
+        subdiv_ccg, key, grids[i], limit_positions.slice(start, key.grid_area));
   }
 }