Sculpt: Enable Cloth Simulation Target for Pose and Boundary

This adds a new brush property called "Deformation Target" which
controls how the brush deformations is going to affect the mesh data. By
default is set to Geometry, which makes the brushes displace the
vertices. When set to Cloth Simulation, the deformation of the brush is
applied to the cloth solver constraints, so the simulation is
responsible to apply the final deformation. This allows to add cloth
simulation effects to other sculpt tools with minor modifications to their
code.

This patch enables Cloth Simulation deformation target for Pose and
Boundary brushes, which are tools that are already designed to work in
low poly counts and produce large deformations. This allows creating the
most common cloth effects, like bending and compressing folds, without
relying on collisions.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D8578

1 files changed, 31 insertions, 1 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 5d09109c506..e1c1b8ee5fb 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -275,6 +275,19 @@ void SCULPT_active_vertex_normal_get(SculptSession *ss, float normal[3])
   SCULPT_vertex_normal_get(ss, SCULPT_active_vertex_get(ss), normal);
 }
 
+float *SCULPT_brush_deform_target_vertex_co_get(SculptSession *ss,
+                                                const int deform_target,
+                                                PBVHVertexIter *iter)
+{
+  switch (deform_target) {
+    case BRUSH_DEFORM_TARGET_GEOMETRY:
+      return iter->co;
+    case BRUSH_DEFORM_TARGET_CLOTH_SIM:
+      return ss->cache->cloth_sim->deformation_pos[iter->index];
+  }
+  return iter->co;
+}
+
 /* Sculpt Face Sets and Visibility. */
 
 int SCULPT_active_face_set_get(SculptSession *ss)
@@ -5690,6 +5703,16 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush, UnifiedPaintSe
       SCULPT_pose_brush_init(sd, ob, ss, brush);
     }
 
+    if (brush->deform_target == BRUSH_DEFORM_TARGET_CLOTH_SIM) {
+      if (!ss->cache->cloth_sim) {
+        ss->cache->cloth_sim = SCULPT_cloth_brush_simulation_create(ss, brush, 1.0f, 0.0f, false);
+        SCULPT_cloth_brush_simulation_init(ss, ss->cache->cloth_sim);
+        SCULPT_cloth_brush_build_nodes_constraints(
+            sd, ob, nodes, totnode, ss->cache->cloth_sim, ss->cache->location, FLT_MAX);
+      }
+      SCULPT_cloth_brush_store_simulation_state(ss, ss->cache->cloth_sim);
+    }
+
     bool invert = ss->cache->pen_flip || ss->cache->invert || brush->flag & BRUSH_DIR_IN;
 
     /* Apply one type of brush action. */
@@ -5828,6 +5851,12 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush, UnifiedPaintSe
       do_gravity(sd, ob, nodes, totnode, sd->gravity_factor);
     }
 
+    if (brush->deform_target == BRUSH_DEFORM_TARGET_CLOTH_SIM) {
+      if (SCULPT_stroke_is_main_symmetry_pass(ss->cache)) {
+        SCULPT_cloth_brush_do_simulation_step(sd, ob, ss->cache->cloth_sim, nodes, totnode);
+      }
+    }
+
     MEM_SAFE_FREE(nodes);
 
     /* Update average stroke position. */
@@ -7308,7 +7337,8 @@ static void sculpt_brush_stroke_init(bContext *C, wmOperator *op)
     need_mask = true;
   }
 
-  if (brush->sculpt_tool == SCULPT_TOOL_CLOTH) {
+  if (brush->sculpt_tool == SCULPT_TOOL_CLOTH ||
+      brush->deform_target == BRUSH_DEFORM_TARGET_CLOTH_SIM) {
     need_mask = true;
   }