@@ -1526,0 +1555,4 @@
+   * Normally this should not be a problem, but just in case ensure that:
+   * - All splits between the head and the primary point away from the head.
+   * - All splits between the tail and the primary point towards the tail.
+   * - The primary split plane conforms to both requirements.

@@ -1643,0 +1776,4 @@
+  int stack_idx[MAX_BBONE_SUBDIV];
+  int start, end, bias, stack_ptr = 0;
+
+  /* Do the first split at the specified joint index. */

@@ -183,0 +185,4 @@
+  float point[3];
+  float tangent[3];
+  /* Dot product of point and tangent to speed up distance computation. */
+  float plane_bias;

@@ -183,0 +188,4 @@
+  float plane_bias;
+
+  /* Inverse width of the smoothing at this level in head-tail space.
+   * Hack: this value is actually indexed by bsp depth (0 to bsp_depth-1), not joint index.

@@ -192,0 +205,4 @@
+  /* Index of the primary split plane joint, or -1 if linear mode. */
+  short bbone_primary_split;
+  /* Maximum number of levels in the joint BSP tree. */
+  short bbone_bsp_depth;

@@ -192,0 +207,4 @@
+  /* Maximum number of levels in the joint BSP tree. */
+  short bbone_bsp_depth;
+  /* Inverse of the total length of the segment polyline. */
+  float bbone_segment_scale;

@@ -1643,0 +1735,4 @@
+  /* Perform a BSP binary search to narrow things down to one segment.
+   * Checked BSP planes are stored for the smoothing pass later. */
+  float boundary_dist[MAX_BBONE_SUBDIV + 1];
+  int stack_idx[MAX_BBONE_SUBDIV];

@@ -1643,0 +1776,4 @@
+    const float d1 = fabsf(boundary_dist[start]);
+    const float d2 = fabsf(boundary_dist[end]);
+
+    head_tail = segment_size * (start * d2 + end * d1) / (d1 + d2);

@@ -1643,0 +1779,4 @@
+    head_tail = segment_size * (start * d2 + end * d1) / (d1 + d2);
+  }
+
+  /* Smooth the mapping to suppress discontinuities by using BSP boundaries up the stack.

@@ -183,0 +184,4 @@
+  /* Boundary data in pose space. */
+  float point[3];
+  float plane_normal[3];
+  /* Dot product of point and tangent to speed up distance computation. */

@@ -1088,0 +1090,4 @@
+       "STRAIGHT",
+       0,
+       "Straight",
+       "Fast mapping method that ignores the rest pose curvature of the B-Bone"},

@@ -1507,3 +1508,3 @@
 }
 
-static void allocate_bbone_cache(bPoseChannel *pchan, int segments)
+static void allocate_bbone_cache(bPoseChannel *pchan, int segments, bool joints)

@@ -1524,2 +1525,4 @@
         1 + uint(segments), sizeof(DualQuat), "bPoseChannel_Runtime::bbone_dual_quats"));
   }
+
+  if (joints && !runtime->bbone_segment_joints) {

@@ -1526,0 +1533,4 @@
+  }
+}
+
+static bool compute_bbone_joint_planes(bPoseChannel *pchan)

@@ -1526,0 +1555,4 @@
+    joints[i].plane_offset = dot_v3v3(joints[i].point, joints[i].plane_normal);
+  }
+
+  /* Precompute the (inverted) length of the curve. */

@@ -1526,0 +1568,4 @@
+   * The actual space partitioning includes two extra virtual segments for the ends. */
+  const int bsp_depth = int(ceilf(log2f(bone->segments + 2)));
+
+  /* Maximum half-width of the smoothing band at the primary split, in segments. */

@@ -1526,0 +1569,4 @@
+  const int bsp_depth = int(ceilf(log2f(bone->segments + 2)));
+
+  /* Maximum half-width of the smoothing band at the primary split, in segments. */
+  const float bone_length = len_v3v3(joints[0].point, joints[bone->segments].point);

@@ -1526,0 +1570,4 @@
+
+  /* Maximum half-width of the smoothing band at the primary split, in segments. */
+  const float bone_length = len_v3v3(joints[0].point, joints[bone->segments].point);
+  const float max_depth_scale = bone->segments * (bone_length / length_sum) * 0.222f;

@@ -1526,0 +1572,4 @@
+  const float bone_length = len_v3v3(joints[0].point, joints[bone->segments].point);
+  const float max_depth_scale = bone->segments * (bone_length / length_sum) * 0.222f;
+
+  /* Per-layer scaling factor, aiming to reduce width to 1 at innermost layer. */

@@ -1526,0 +1573,4 @@
+  const float max_depth_scale = bone->segments * (bone_length / length_sum) * 0.222f;
+
+  /* Per-layer scaling factor, aiming to reduce width to 1 at innermost layer. */
+  const float scale_factor = powf(max_ff(max_depth_scale, 1.0f), 1.0f / (bsp_depth - 1));

@@ -1547,2 +1608,4 @@
   BKE_pchan_bbone_spline_setup(pchan, true, true, b_bone_rest);
 
+  /* Compute joint planes. */
+  runtime->bbone_use_bsp_mapping = use_joints && compute_bbone_joint_planes(pchan);

@@ -1599,0 +1665,4 @@
+
+    runtime->bbone_use_bsp_mapping = use_bsp_mapping;
+
+    if (use_bsp_mapping) {

@@ -1629,2 +1703,2 @@
-                                          int *r_index,
-                                          float *r_blend_next)
+/** Implementation of the Straight B-Bone segment mapping. */
+static void find_bbone_segment_index_simple(const bPoseChannel *pchan,

@@ -1640,6 +1717,138 @@ void BKE_pchan_bbone_deform_segment_index(const bPoseChannel *pchan,
       pchan, y / pchan->bone->length, r_index, r_blend_next);
 }
 
+/** Computes signed distance to the plane perpendicular to the joint tangent. */

@@ -1641,2 +1718,4 @@
 }
 
+/** Computes signed distance to the plane perpendicular to the joint tangent. */
+inline float bbone_segment_bsp_side(const bPoseChannel_BBoneSegmentJoint &joint, const float *co)

@@ -1643,0 +1724,4 @@
+}
+
+/** Implementation of the Curved B-Bone segment mapping. */
+static void find_bbone_segment_index_bsp(const bPoseChannel *pchan,

@@ -1643,0 +1735,4 @@
+  /* Perform a BSP binary search to narrow things down to one segment.
+   * Checked BSP planes are stored for the smoothing pass later. */
+  float boundary_dist[MAX_BBONE_SUBDIV + 1];
+  int boundary_idx_stack[MAX_BBONE_SUBDIV];

@@ -1643,0 +1794,4 @@
+    /* Boundary in the head-tail space. */
+    const float boundary_pos = boundary_idx * segment_size;
+
+    /* Distance of the original 3d point from the boundary plane,

@@ -1643,0 +1824,4 @@
+
+    /* Smooth the distance based coefficient around zero. */
+    const float dist_coeff_smooth = dist_coeff * dist_coeff * (7.0f + 1.0f) /
+                                    (7.0f * dist_coeff + 1.0f);

@@ -180,6 +180,19 @@ typedef struct bPoseChannelDrawData {
 struct DualQuat;
 struct Mat4;
 
+typedef struct bPoseChannel_BBoneSegmentJoint {

@@ -183,0 +188,4 @@
+  float plane_offset;
+
+  /* Inverse width of the smoothing at this level in head-tail space.
+   * Optimization: this value is actually indexed by bsp depth (0 to bsp_depth-1), not joint

@@ -198,1 +218,4 @@
   struct DualQuat *bbone_dual_quats;
+
+  /* Segment boundaries for curved mode. */
+  struct bPoseChannel_BBoneSegmentJoint *bbone_segment_joints;

@@ -82,2 +82,4 @@
   float oldlength;
 
+  /** Mapping of vertices to segments. */
+  char bbone_mapping_mode;

@@ -1602,0 +1684,4 @@
+    if (use_curved_mapping) {
+      runtime->bbone_arc_length_reciprocal = runtime_from->bbone_arc_length_reciprocal;
+
+      memcpy(runtime->bbone_segment_boundaries,

@@ -1646,0 +1753,4 @@
+  float boundary_dist[MAX_BBONE_SUBDIV + 1];
+
+  /* Stack of BSP plane indices that were checked in the binary search. */
+  int boundary_idx_stack[MAX_BBONE_SUBDIV];

@@ -1602,0 +1682,4 @@
+      memcpy(runtime->bbone_segment_boundaries,
+             runtime_from->bbone_segment_boundaries,
+             sizeof(bPoseChannel_BBoneSegmentBoundary) * (1 + segments));
+    }