Sculpt: Multires Displacement Smear

This tool implements smearing for multires displacement over the limit
surface, similar to how smearing for colors and topology slide works.
When used the displacement values of the vertices "slide" over the
topology, creating the effect of smearing the surface detail.

As the brush just modifies displacement values instead of coordinates,
the total displacement of the affected area doesn't change. This means
that this smearing effect can be used multiple times over the same area
without generating any artifacts in the topology.

When the brush is used with the pinch or expand smear modes,
displacement differences are pushed into the same area, creating hard
surface effects without pinching the topology.

As any other brush that relies on the limit surface (like displacement
erasers), this will work better after using apply base.

Reviewed By: sergey, JulienKaspar, dbystedt

Differential Revision: https://developer.blender.org/D9659

8 files changed, 179 insertions, 1 deletions

diff --git a/release/scripts/startup/bl_ui/properties_paint_common.py b/release/scripts/startup/bl_ui/properties_paint_common.py
index 86221ebce59..5d241e8e216 100644
--- a/release/scripts/startup/bl_ui/properties_paint_common.py
+++ b/release/scripts/startup/bl_ui/properties_paint_common.py
@@ -764,6 +764,10 @@ def brush_settings(layout, context, brush, popover=False):
                 col.prop(brush, "surface_smooth_current_vertex")
                 col.prop(brush, "surface_smooth_iterations")
 
+        elif sculpt_tool == 'DISPLACEMENT_SMEAR':
+            col = layout.column()
+            col.prop(brush, "smear_deform_type")
+
         elif sculpt_tool == 'MASK':
             layout.row().prop(brush, "mask_tool", expand=True)
 
diff --git a/source/blender/blenkernel/intern/brush.c b/source/blender/blenkernel/intern/brush.c
index 33686cea4fc..9a954a89cad 100644
--- a/source/blender/blenkernel/intern/brush.c
+++ b/source/blender/blenkernel/intern/brush.c
@@ -1834,6 +1834,14 @@ void BKE_brush_sculpt_reset(Brush *br)
       br->flag &= ~BRUSH_SPACE_ATTEN;
       br->curve_preset = BRUSH_CURVE_SPHERE;
       break;
+    case SCULPT_TOOL_DISPLACEMENT_SMEAR:
+      br->alpha = 1.0f;
+      br->spacing = 5;
+      br->hardness = 0.7f;
+      br->flag &= ~BRUSH_ALPHA_PRESSURE;
+      br->flag &= ~BRUSH_SPACE_ATTEN;
+      br->curve_preset = BRUSH_CURVE_SMOOTHER;
+      break;
     default:
       break;
   }
@@ -1898,6 +1906,7 @@ void BKE_brush_sculpt_reset(Brush *br)
     case SCULPT_TOOL_MASK:
     case SCULPT_TOOL_DRAW_FACE_SETS:
     case SCULPT_TOOL_DISPLACEMENT_ERASER:
+    case SCULPT_TOOL_DISPLACEMENT_SMEAR:
       br->add_col[0] = 0.75f;
       br->add_col[1] = 0.75f;
       br->add_col[2] = 0.75f;
diff --git a/source/blender/blenloader/intern/versioning_defaults.c b/source/blender/blenloader/intern/versioning_defaults.c
index 2d75b046366..198f65b9794 100644
--- a/source/blender/blenloader/intern/versioning_defaults.c
+++ b/source/blender/blenloader/intern/versioning_defaults.c
@@ -739,6 +739,14 @@ void BLO_update_defaults_startup_blend(Main *bmain, const char *app_template)
       brush->sculpt_tool = SCULPT_TOOL_DISPLACEMENT_ERASER;
     }
 
+    brush_name = "Multires Displacement Smear";
+    brush = BLI_findstring(&bmain->brushes, brush_name, offsetof(ID, name) + 2);
+    if (!brush) {
+      brush = BKE_brush_add(bmain, brush_name, OB_MODE_SCULPT);
+      id_us_min(&brush->id);
+      brush->sculpt_tool = SCULPT_TOOL_DISPLACEMENT_SMEAR;
+    }
+
     /* Use the same tool icon color in the brush cursor */
     for (brush = bmain->brushes.first; brush; brush = brush->id.next) {
       if (brush->ob_mode & OB_MODE_SCULPT) {
diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 80a32682325..26db2673335 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -1227,6 +1227,7 @@ static bool sculpt_tool_is_proxy_used(const char sculpt_tool)
               SCULPT_TOOL_SMOOTH,
               SCULPT_TOOL_LAYER,
               SCULPT_TOOL_POSE,
+              SCULPT_TOOL_DISPLACEMENT_SMEAR,
               SCULPT_TOOL_BOUNDARY,
               SCULPT_TOOL_CLOTH,
               SCULPT_TOOL_PAINT,
@@ -2362,6 +2363,7 @@ static float brush_strength(const Sculpt *sd,
       final_pressure = pressure * pressure;
       return final_pressure * overlap * feather;
     case SCULPT_TOOL_SMEAR:
+    case SCULPT_TOOL_DISPLACEMENT_SMEAR:
       return alpha * pressure * overlap * feather;
     case SCULPT_TOOL_CLAY_STRIPS:
       /* Clay Strips needs less strength to compensate the curve. */
@@ -3103,6 +3105,147 @@ static void do_displacement_eraser_brush(Sculpt *sd, Object *ob, PBVHNode **node
 
 /** \} */
 
+/** \name Sculpt Multires Displacement Smear Brush
+ * \{ */
+
+static void do_displacement_smear_brush_task_cb_ex(void *__restrict userdata,
+                                                   const int n,
+                                                   const TaskParallelTLS *__restrict tls)
+{
+  SculptThreadedTaskData *data = userdata;
+  SculptSession *ss = data->ob->sculpt;
+  const Brush *brush = data->brush;
+  const float bstrength = clamp_f(ss->cache->bstrength, 0.0f, 1.0f);
+
+  SculptBrushTest test;
+  SculptBrushTestFn sculpt_brush_test_sq_fn = SCULPT_brush_test_init_with_falloff_shape(
+      ss, &test, data->brush->falloff_shape);
+  const int thread_id = BLI_task_parallel_thread_id(tls);
+
+  PBVHVertexIter vd;
+  BKE_pbvh_vertex_iter_begin(ss->pbvh, data->nodes[n], vd, PBVH_ITER_UNIQUE)
+  {
+    if (!sculpt_brush_test_sq_fn(&test, vd.co)) {
+      continue;
+    }
+    const float fade = bstrength * SCULPT_brush_strength_factor(ss,
+                                                                brush,
+                                                                vd.co,
+                                                                sqrtf(test.dist),
+                                                                vd.no,
+                                                                vd.fno,
+                                                                vd.mask ? *vd.mask : 0.0f,
+                                                                vd.index,
+                                                                thread_id);
+
+    float current_disp[3];
+    float current_disp_norm[3];
+    float interp_limit_surface_disp[3];
+
+    copy_v3_v3(interp_limit_surface_disp, ss->cache->prev_displacement[vd.index]);
+
+    switch (brush->smear_deform_type) {
+      case BRUSH_SMEAR_DEFORM_DRAG:
+        sub_v3_v3v3(current_disp, ss->cache->location, ss->cache->last_location);
+        break;
+      case BRUSH_SMEAR_DEFORM_PINCH:
+        sub_v3_v3v3(current_disp, ss->cache->location, vd.co);
+        break;
+      case BRUSH_SMEAR_DEFORM_EXPAND:
+        sub_v3_v3v3(current_disp, vd.co, ss->cache->location);
+        break;
+    }
+
+    normalize_v3_v3(current_disp_norm, current_disp);
+    mul_v3_v3fl(current_disp, current_disp_norm, ss->cache->bstrength);
+
+    float weights_accum = 1.0f;
+
+    SculptVertexNeighborIter ni;
+    SCULPT_VERTEX_NEIGHBORS_ITER_BEGIN (ss, vd.index, ni) {
+      float vertex_disp[3];
+      float vertex_disp_norm[3];
+      float neighbor_limit_co[3];
+      SCULPT_vertex_limit_surface_get(ss, ni.index, neighbor_limit_co);
+      sub_v3_v3v3(vertex_disp,
+                  ss->cache->limit_surface_co[ni.index],
+                  ss->cache->limit_surface_co[vd.index]);
+      const float *neighbor_limit_surface_disp = ss->cache->prev_displacement[ni.index];
+      normalize_v3_v3(vertex_disp_norm, vertex_disp);
+      if (dot_v3v3(current_disp_norm, vertex_disp_norm) < 0.0f) {
+        const float disp_interp = clamp_f(
+            -dot_v3v3(current_disp_norm, vertex_disp_norm), 0.0f, 1.0f);
+        madd_v3_v3fl(interp_limit_surface_disp, neighbor_limit_surface_disp, disp_interp);
+        weights_accum += disp_interp;
+      }
+    }
+    SCULPT_VERTEX_NEIGHBORS_ITER_END(ni);
+
+    mul_v3_fl(interp_limit_surface_disp, 1.0f / weights_accum);
+
+    float new_co[3];
+    add_v3_v3v3(new_co, ss->cache->limit_surface_co[vd.index], interp_limit_surface_disp);
+    interp_v3_v3v3(vd.co, vd.co, new_co, fade);
+
+    if (vd.mvert) {
+      vd.mvert->flag |= ME_VERT_PBVH_UPDATE;
+    }
+  }
+  BKE_pbvh_vertex_iter_end;
+}
+
+static void do_displacement_smear_store_prev_disp_task_cb_ex(
+    void *__restrict userdata, const int n, const TaskParallelTLS *__restrict UNUSED(tls))
+{
+  SculptThreadedTaskData *data = userdata;
+  SculptSession *ss = data->ob->sculpt;
+
+  PBVHVertexIter vd;
+  BKE_pbvh_vertex_iter_begin(ss->pbvh, data->nodes[n], vd, PBVH_ITER_UNIQUE)
+  {
+    sub_v3_v3v3(ss->cache->prev_displacement[vd.index],
+                SCULPT_vertex_co_get(ss, vd.index),
+                ss->cache->limit_surface_co[vd.index]);
+  }
+  BKE_pbvh_vertex_iter_end;
+}
+
+static void do_displacement_smear_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
+{
+  Brush *brush = BKE_paint_brush(&sd->paint);
+  SculptSession *ss = ob->sculpt;
+
+  BKE_curvemapping_init(brush->curve);
+
+  const int totvert = SCULPT_vertex_count_get(ss);
+  if (!ss->cache->prev_displacement) {
+    ss->cache->prev_displacement = MEM_malloc_arrayN(
+        totvert, sizeof(float[3]), "prev displacement");
+    ss->cache->limit_surface_co = MEM_malloc_arrayN(totvert, sizeof(float[3]), "limit surface co");
+    for (int i = 0; i < totvert; i++) {
+      SCULPT_vertex_limit_surface_get(ss, i, ss->cache->limit_surface_co[i]);
+      sub_v3_v3v3(ss->cache->prev_displacement[i],
+                  SCULPT_vertex_co_get(ss, i),
+                  ss->cache->limit_surface_co[i]);
+    }
+  }
+  /* Threaded loop over nodes. */
+  SculptThreadedTaskData data = {
+      .sd = sd,
+      .ob = ob,
+      .brush = brush,
+      .nodes = nodes,
+  };
+
+  TaskParallelSettings settings;
+  BKE_pbvh_parallel_range_settings(&settings, true, totnode);
+  BLI_task_parallel_range(
+      0, totnode, &data, do_displacement_smear_store_prev_disp_task_cb_ex, &settings);
+  BLI_task_parallel_range(0, totnode, &data, do_displacement_smear_brush_task_cb_ex, &settings);
+}
+
+/** \} */
+
 static void do_draw_brush_task_cb_ex(void *__restrict userdata,
                                      const int n,
                                      const TaskParallelTLS *__restrict tls)
@@ -5927,6 +6070,9 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush, UnifiedPaintSe
       case SCULPT_TOOL_DISPLACEMENT_ERASER:
         do_displacement_eraser_brush(sd, ob, nodes, totnode);
         break;
+      case SCULPT_TOOL_DISPLACEMENT_SMEAR:
+        do_displacement_smear_brush(sd, ob, nodes, totnode);
+        break;
       case SCULPT_TOOL_PAINT:
         SCULPT_do_paint_brush(sd, ob, nodes, totnode);
         break;
@@ -6490,6 +6636,8 @@ static const char *sculpt_tool_name(Sculpt *sd)
       return "Draw Face Sets";
     case SCULPT_TOOL_DISPLACEMENT_ERASER:
       return "Multires Displacement Eraser";
+    case SCULPT_TOOL_DISPLACEMENT_SMEAR:
+      return "Multires Displacement Smear";
     case SCULPT_TOOL_PAINT:
       return "Paint Brush";
     case SCULPT_TOOL_SMEAR:
@@ -6510,6 +6658,8 @@ void SCULPT_cache_free(StrokeCache *cache)
   MEM_SAFE_FREE(cache->layer_displacement_factor);
   MEM_SAFE_FREE(cache->prev_colors);
   MEM_SAFE_FREE(cache->detail_directions);
+  MEM_SAFE_FREE(cache->prev_displacement);
+  MEM_SAFE_FREE(cache->limit_surface_co);
 
   if (cache->pose_ik_chain) {
     SCULPT_pose_ik_chain_free(cache->pose_ik_chain);
@@ -6681,6 +6831,7 @@ static void sculpt_update_cache_invariants(
                                    SCULPT_TOOL_MASK,
                                    SCULPT_TOOL_SMOOTH,
                                    SCULPT_TOOL_SIMPLIFY,
+                                   SCULPT_TOOL_DISPLACEMENT_SMEAR,
                                    SCULPT_TOOL_DISPLACEMENT_ERASER) &&
                              (sd->gravity_factor > 0.0f));
   /* Get gravity vector in world space. */
diff --git a/source/blender/editors/sculpt_paint/sculpt_intern.h b/source/blender/editors/sculpt_paint/sculpt_intern.h
index 853b221e92a..d1e17c7e59b 100644
--- a/source/blender/editors/sculpt_paint/sculpt_intern.h
+++ b/source/blender/editors/sculpt_paint/sculpt_intern.h
@@ -926,6 +926,10 @@ typedef struct StrokeCache {
 
   float (*prev_colors)[4];
 
+  /* Multires Displacement Smear. */
+  float (*prev_displacement)[3];
+  float (*limit_surface_co)[3];
+
   /* The rest is temporary storage that isn't saved as a property */
 
   bool first_time; /* Beginning of stroke may do some things special */
diff --git a/source/blender/makesdna/DNA_brush_enums.h b/source/blender/makesdna/DNA_brush_enums.h
index 96e870cff8e..f12934c9104 100644
--- a/source/blender/makesdna/DNA_brush_enums.h
+++ b/source/blender/makesdna/DNA_brush_enums.h
@@ -457,6 +457,7 @@ typedef enum eBrushSculptTool {
   SCULPT_TOOL_SMEAR = 29,
   SCULPT_TOOL_BOUNDARY = 30,
   SCULPT_TOOL_DISPLACEMENT_ERASER = 31,
+  SCULPT_TOOL_DISPLACEMENT_SMEAR = 32,
 } eBrushSculptTool;
 
 /* Brush.uv_sculpt_tool */
diff --git a/source/blender/makesdna/DNA_brush_types.h b/source/blender/makesdna/DNA_brush_types.h
index 4b020019062..1709ea5dc63 100644
--- a/source/blender/makesdna/DNA_brush_types.h
+++ b/source/blender/makesdna/DNA_brush_types.h
@@ -373,7 +373,7 @@ typedef struct Brush {
 typedef struct tPaletteColorHSV {
   float rgb[3];
   float value;
-  float h;
+      float h;
   float s;
   float v;
 } tPaletteColorHSV;
diff --git a/source/blender/makesrna/intern/rna_brush.c b/source/blender/makesrna/intern/rna_brush.c
index 08c655d493c..a361feba439 100644
--- a/source/blender/makesrna/intern/rna_brush.c
+++ b/source/blender/makesrna/intern/rna_brush.c
@@ -134,6 +134,7 @@ const EnumPropertyItem rna_enum_brush_sculpt_tool_items[] = {
     {SCULPT_TOOL_SIMPLIFY, "SIMPLIFY", ICON_BRUSH_DATA, "Simplify", ""},
     {SCULPT_TOOL_MASK, "MASK", ICON_BRUSH_MASK, "Mask", ""},
     {SCULPT_TOOL_DISPLACEMENT_ERASER, "DISPLACEMENT_ERASER", ICON_BRUSH_SCULPT_DRAW, "Multires Displacement Eraser", ""},
+    {SCULPT_TOOL_DISPLACEMENT_SMEAR, "DISPLACEMENT_SMEAR", ICON_BRUSH_SCULPT_DRAW, "Multires Displacement Smear", ""},
     {SCULPT_TOOL_PAINT, "PAINT", ICON_BRUSH_SCULPT_DRAW, "Paint", ""},
     {SCULPT_TOOL_SMEAR, "SMEAR", ICON_BRUSH_SCULPT_DRAW, "Smear", ""},
     {SCULPT_TOOL_DRAW_FACE_SETS, "DRAW_FACE_SETS", ICON_BRUSH_MASK, "Draw Face Sets", ""},