Sculpt: Multires Displacement Eraser Brush

This brush deletes displacement information of the Multires Modifier,
resetting the mesh to the subdivision limit surface.
This can be use to easily delete parts of the sculpt or to fix
reprojection artifacts after applying a shrinkwrap.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D8543

2 files changed, 49 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/brush.c b/source/blender/blenkernel/intern/brush.c
index af186dc4940..8cd30c2241f 100644
--- a/source/blender/blenkernel/intern/brush.c
+++ b/source/blender/blenkernel/intern/brush.c
@@ -1481,6 +1481,11 @@ void BKE_brush_sculpt_reset(Brush *br)
       br->curve_preset = BRUSH_CURVE_POW4;
       br->spacing = 5;
       break;
+    case SCULPT_TOOL_DISPLACEMENT_ERASER:
+      br->curve_preset = BRUSH_CURVE_SMOOTHER;
+      br->spacing = 10;
+      br->alpha = 1.0f;
+      break;
     case SCULPT_TOOL_SLIDE_RELAX:
       br->spacing = 10;
       br->alpha = 1.0f;
@@ -1680,6 +1685,7 @@ void BKE_brush_sculpt_reset(Brush *br)
     case SCULPT_TOOL_PAINT:
     case SCULPT_TOOL_MASK:
     case SCULPT_TOOL_DRAW_FACE_SETS:
+    case SCULPT_TOOL_DISPLACEMENT_ERASER:
       br->add_col[0] = 0.75f;
       br->add_col[1] = 0.75f;
       br->add_col[2] = 0.75f;
diff --git a/source/blender/blenkernel/intern/subdiv_ccg.c b/source/blender/blenkernel/intern/subdiv_ccg.c
index ea8bae4737a..0997b42a19f 100644
--- a/source/blender/blenkernel/intern/subdiv_ccg.c
+++ b/source/blender/blenkernel/intern/subdiv_ccg.c
@@ -1933,4 +1933,47 @@ void BKE_subdiv_ccg_grid_hidden_ensure(SubdivCCG *subdiv_ccg, int grid_index)
   subdiv_ccg->grid_hidden[grid_index] = BLI_BITMAP_NEW(key.grid_area, __func__);
 }
 
+static void subdiv_ccg_coord_to_ptex_coord(const SubdivCCG *subdiv_ccg,
+                                           const SubdivCCGCoord *coord,
+                                           int *r_ptex_face_index,
+                                           float *r_u,
+                                           float *r_v)
+{
+  Subdiv *subdiv = subdiv_ccg->subdiv;
+
+  const float grid_size = subdiv_ccg->grid_size;
+  const float grid_size_1_inv = 1.0f / (grid_size - 1);
+
+  const float grid_u = coord->x * grid_size_1_inv;
+  const float grid_v = coord->y * grid_size_1_inv;
+
+  const int face_index = BKE_subdiv_ccg_grid_to_face_index(subdiv_ccg, coord->grid_index);
+  const SubdivCCGFace *faces = subdiv_ccg->faces;
+  const SubdivCCGFace *face = &faces[face_index];
+  const int *face_ptex_offset = BKE_subdiv_face_ptex_offset_get(subdiv);
+  *r_ptex_face_index = face_ptex_offset[face_index];
+
+  const float corner = coord->grid_index - face->start_grid_index;
+
+  if (face->num_grids == 4) {
+    BKE_subdiv_rotate_grid_to_quad(corner, grid_u, grid_v, r_u, r_v);
+  }
+  else {
+    *r_ptex_face_index += corner;
+    *r_u = 1.0f - grid_v;
+    *r_v = 1.0f - grid_u;
+  }
+}
+
+void BKE_subdiv_ccg_eval_limit_point(const SubdivCCG *subdiv_ccg,
+                                     const SubdivCCGCoord *coord,
+                                     float r_point[3])
+{
+  Subdiv *subdiv = subdiv_ccg->subdiv;
+  int ptex_face_index;
+  float u, v;
+  subdiv_ccg_coord_to_ptex_coord(subdiv_ccg, coord, &ptex_face_index, &u, &v);
+  BKE_subdiv_eval_limit_point(subdiv, ptex_face_index, u, v, r_point);
+}
+
 /** \} */