Sculpt: Pose Brush option to affect loose parts

This option allows posing meshes with different disconnected elements
using the Pose Brush.

This is achieved by doing the following:
- Creating an ID per vertex that stores the connected component of that vertex.
- By using those IDs, one fake topology connection is created per vertex to the nearest vertex in a different ID. The maximum distance to create that connection is determined by the "Max Element Distance" property. These fake connectivity neighbors are used in the Sculpt API functions iterators, so all the algorithms of the Pose Brush can run without modifications as if everything was part of the same mesh.

In order to make this work, the "Connected only" property of the Pose Brush needs to be disabled. This will add an extra performance cost to the Pose Brush and its preview. To achieve optimal results, max element distance should be as low as possible.

Reviewed By: sergey, campbellbarton

Differential Revision: https://developer.blender.org/D7282

1 files changed, 19 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_paint.h b/source/blender/blenkernel/BKE_paint.h
index 21195566179..c36e9f6961f 100644
--- a/source/blender/blenkernel/BKE_paint.h
+++ b/source/blender/blenkernel/BKE_paint.h
@@ -289,6 +289,22 @@ typedef struct SculptLayerPersistentBase {
   float disp;
 } SculptLayerPersistentBase;
 
+typedef struct SculptVertexInfo {
+  /* Idexed by vertex, stores and ID of its topologycally connected component. */
+  int *connected_component;
+} SculptVertexInfo;
+
+typedef struct SculptFakeNeighbors {
+  bool use_fake_neighbors;
+
+  /* Max distance used to calculate neighborhood information. */
+  float current_max_distance;
+
+  /* Idexed by vertex, stores the vertex index of its fake neighbor if available. */
+  int *fake_neighbor_index;
+
+} SculptFakeNeighbors;
+
 /* Session data (mode-specific) */
 
 typedef struct SculptSession {
@@ -380,6 +396,9 @@ typedef struct SculptSession {
   /* This is freed with the PBVH, so it is always in sync with the mesh. */
   SculptLayerPersistentBase *layer_base;
 
+  SculptVertexInfo vertex_info;
+  SculptFakeNeighbors fake_neighbors;
+
   /* Transform operator */
   float pivot_pos[3];
   float pivot_rot[4];