Sculpt: Elastic deform type for Snake Hook

This adds deformation types to snake hook and the elastic deformation
type. This mode deforms the mesh using a kelvinlet instead of applying
the displacement directly inside the brush radius, which is great for
stylized shapes sketching.

Changes in rake rotation when using elastic are too strong when set
to 1, so I'll add a nicer way to support rake rotations with smoother
transitions in the future.

Reviewed By: sergey, JulienKaspar

Differential Revision: https://developer.blender.org/D9560

1 files changed, 32 insertions, 0 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_intern.h b/source/blender/editors/sculpt_paint/sculpt_intern.h
index 99ee22328ea..3b48207f461 100644
--- a/source/blender/editors/sculpt_paint/sculpt_intern.h
+++ b/source/blender/editors/sculpt_paint/sculpt_intern.h
@@ -434,6 +434,38 @@ BLI_INLINE bool SCULPT_is_cloth_deform_brush(const Brush *brush)
           brush->deform_target == BRUSH_DEFORM_TARGET_CLOTH_SIM);
 }
 
+BLI_INLINE bool SCULPT_tool_needs_all_pbvh_nodes(const Brush *brush)
+{
+  if (brush->sculpt_tool == SCULPT_TOOL_ELASTIC_DEFORM) {
+    /* Elastic deformations in any brush need all nodes to avoid artifacts as the effect
+     * of the Kelvinlet is not constrained by the radius. */
+    return true;
+  }
+
+  if (brush->sculpt_tool == SCULPT_TOOL_POSE) {
+    /* Pose needs all nodes because it applies all symmetry iterations at the same time
+     * and the IK chain can grow to any area of the model. */
+    /* TODO: This can be optimized by filtering the nodes after calculating the chain. */
+    return true;
+  }
+
+  if (brush->sculpt_tool == SCULPT_TOOL_BOUNDARY) {
+    /* Boundary needs all nodes because it is not possible to know where the boundary
+     * deformation is going to be propagated before calculating it. */
+    /* TODO: after calculating the boudnary info in the first iteration, it should be
+     * possible to get the nodes that have vertices included in any boundary deformation
+     * and cache them. */
+    return true;
+  }
+
+  if (brush->sculpt_tool == SCULPT_TOOL_SNAKE_HOOK &&
+      brush->snake_hook_deform_type == BRUSH_SNAKE_HOOK_DEFORM_ELASTIC) {
+    /* Snake hook in elastic deform type has same requirements as the elastic deform tool. */
+    return true;
+  }
+  return false;
+}
+
 /* Pose Brush. */
 void SCULPT_do_pose_brush(struct Sculpt *sd,
                           struct Object *ob,