Bendy Bones: Advanced B-Bones for Easier + Simple Rigging

This commit/patch/branch brings a bunch of powerful new options for B-Bones and
for working with B-Bones, making it easier for animators to create their own
rigs, using fewer bones (which also means hopefully lighter + faster rigs ;)
This functionality was first demoed by Daniel at BConf15

Some highlights from this patch include:
* You can now directly control the shape of B-Bones using a series of properties
  instead of being restricted to trying to indirectly control them through the
  neighbouring bones.  See the "Bendy Bones" panel...

* B-Bones can be shaped in EditMode to define a "curved rest pose" for the bone.
  This is useful for things like eyebrows and mouths/eyelids

* You can now make B-Bones use custom bones as their reference bone handles,
  instead of only using the parent/child bones. To do so, enable the
  "Use Custom Reference Handles" toggle. If none are specified, then the BBone will
  only use the Bendy Bone properties.

* Constraints Head/Tail option can now slide along the B-Bone shape, instead of
  just linearly interpolating between the endpoints of the bone.

For more details, see:
* http://aligorith.blogspot.co.nz/2016/05/bendy-bones-dev-update.html
* http://aligorith.blogspot.co.nz/2016/05/an-in-depth-look-at-how-b-bones-work.html



-- Credits --
Original Idea: Daniel M Lara (pepeland)
Original Patch/Research: Jose Molina
Additional Development + Polish: Joshua Leung (aligorith)
Testing/Feedback: Daniel M Lara (pepeland), Juan Pablo Bouza (jpbouza)

1 files changed, 90 insertions, 8 deletions

diff --git a/source/blender/editors/space_view3d/drawarmature.c b/source/blender/editors/space_view3d/drawarmature.c
index 5cda721be44..f7c1e2ee981 100644
--- a/source/blender/editors/space_view3d/drawarmature.c
+++ b/source/blender/editors/space_view3d/drawarmature.c
@@ -53,6 +53,7 @@
 #include "BKE_global.h"
 #include "BKE_modifier.h"
 #include "BKE_nla.h"
+#include "BKE_curve.h"
 
 
 #include "BIF_gl.h"
@@ -1093,20 +1094,101 @@ static void draw_line_bone(int armflag, int boneflag, short constflag, unsigned
 	glPopMatrix();
 }
 
-static void draw_b_bone_boxes(const short dt, bPoseChannel *pchan, float xwidth, float length, float zwidth)
+/* A partial copy of b_bone_spline_setup(), with just the parts for previewing editmode curve settings 
+ *
+ * This assumes that prev/next bones don't have any impact (since they should all still be in the "straight"
+ * position here anyway), and that we can simply apply the bbone settings to get the desired effect...
+ */
+static void ebone_spline_preview(EditBone *ebone, Mat4 result_array[MAX_BBONE_SUBDIV])
+{
+	float h1[3], h2[3], length, hlength1, hlength2, roll1 = 0.0f, roll2 = 0.0f;
+	float mat3[3][3];
+	float data[MAX_BBONE_SUBDIV + 1][4], *fp;
+	int a;
+	
+	length = ebone->length;
+	
+	hlength1 = ebone->ease1 * length * 0.390464f; /* 0.5f * sqrt(2) * kappa, the handle length for near-perfect circles */
+	hlength2 = ebone->ease2 * length * 0.390464f;
+	
+	/* find the handle points, since this is inside bone space, the
+	 * first point = (0, 0, 0)
+	 * last point =  (0, length, 0)
+	 *
+	 * we also just apply all the "extra effects", since they're the whole reason we're doing this...
+	 */
+	h1[0] = ebone->curveInX;
+	h1[1] = hlength1;
+	h1[2] = ebone->curveInY;
+	roll1 = ebone->roll1;
+	
+	h2[0] = ebone->curveOutX;
+	h2[1] = -hlength2;
+	h2[2] = ebone->curveOutY;
+	roll2 = ebone->roll2;
+	
+	/* make curve */
+	if (ebone->segments > MAX_BBONE_SUBDIV)
+		ebone->segments = MAX_BBONE_SUBDIV;
+
+	BKE_curve_forward_diff_bezier(0.0f,  h1[0],                               h2[0],                               0.0f,   data[0],     MAX_BBONE_SUBDIV, 4 * sizeof(float));
+	BKE_curve_forward_diff_bezier(0.0f,  h1[1],                               length + h2[1],                      length, data[0] + 1, MAX_BBONE_SUBDIV, 4 * sizeof(float));
+	BKE_curve_forward_diff_bezier(0.0f,  h1[2],                               h2[2],                               0.0f,   data[0] + 2, MAX_BBONE_SUBDIV, 4 * sizeof(float));
+	BKE_curve_forward_diff_bezier(roll1, roll1 + 0.390464f * (roll2 - roll1), roll2 - 0.390464f * (roll2 - roll1), roll2,  data[0] + 3, MAX_BBONE_SUBDIV, 4 * sizeof(float));
+
+	equalize_bbone_bezier(data[0], ebone->segments); /* note: does stride 4! */
+
+	/* make transformation matrices for the segments for drawing */
+	for (a = 0, fp = data[0]; a < ebone->segments; a++, fp += 4) {
+		sub_v3_v3v3(h1, fp + 4, fp);
+		vec_roll_to_mat3(h1, fp[3], mat3); /* fp[3] is roll */
+		
+		copy_m4_m3(result_array[a].mat, mat3);
+		copy_v3_v3(result_array[a].mat[3], fp);
+		
+		/* "extra" scale facs... */
+		{
+			const int num_segments = ebone->segments;
+			
+			const float scaleFactorIn  = 1.0f + (ebone->scaleIn  - 1.0f) * ((float)(num_segments - a) / (float)num_segments);
+			const float scaleFactorOut = 1.0f + (ebone->scaleOut - 1.0f) * ((float)(a + 1)            / (float)num_segments);
+			
+			const float scalefac = scaleFactorIn * scaleFactorOut;
+			float bscalemat[4][4], bscale[3];
+			
+			bscale[0] = scalefac;
+			bscale[1] = 1.0f;
+			bscale[2] = scalefac;
+			
+			size_to_mat4(bscalemat, bscale);
+			
+			/* Note: don't multiply by inverse scale mat here, as it causes problems with scaling shearing and breaking segment chains */
+			mul_m4_series(result_array[a].mat, result_array[a].mat, bscalemat);
+		}
+	}
+}
+
+static void draw_b_bone_boxes(const short dt, bPoseChannel *pchan, EditBone *ebone, float xwidth, float length, float zwidth)
 {
 	int segments = 0;
 	
 	if (pchan) 
 		segments = pchan->bone->segments;
+	else if (ebone)
+		segments = ebone->segments;
 	
-	if ((segments > 1) && (pchan)) {
+	if (segments > 1) {
 		float dlen = length / (float)segments;
 		Mat4 bbone[MAX_BBONE_SUBDIV];
 		int a;
-
-		b_bone_spline_setup(pchan, 0, bbone);
-
+		
+		if (pchan) {
+			b_bone_spline_setup(pchan, 0, bbone);
+		}
+		else if (ebone) {
+			ebone_spline_preview(ebone, bbone);
+		}
+		
 		for (a = 0; a < segments; a++) {
 			glPushMatrix();
 			glMultMatrixf(bbone[a].mat);
@@ -1177,7 +1259,7 @@ static void draw_b_bone(const short dt, int armflag, int boneflag, short constfl
 		else
 			UI_ThemeColor(TH_BONE_SOLID);
 		
-		draw_b_bone_boxes(OB_SOLID, pchan, xwidth, length, zwidth);
+		draw_b_bone_boxes(OB_SOLID, pchan, ebone, xwidth, length, zwidth);
 		
 		/* disable solid drawing */
 		GPU_basic_shader_bind(GPU_SHADER_USE_COLOR);
@@ -1190,7 +1272,7 @@ static void draw_b_bone(const short dt, int armflag, int boneflag, short constfl
 				if (set_pchan_glColor(PCHAN_COLOR_CONSTS, boneflag, constflag)) {
 					glEnable(GL_BLEND);
 					
-					draw_b_bone_boxes(OB_SOLID, pchan, xwidth, length, zwidth);
+					draw_b_bone_boxes(OB_SOLID, pchan, ebone, xwidth, length, zwidth);
 					
 					glDisable(GL_BLEND);
 				}
@@ -1200,7 +1282,7 @@ static void draw_b_bone(const short dt, int armflag, int boneflag, short constfl
 			}
 		}
 		
-		draw_b_bone_boxes(OB_WIRE, pchan, xwidth, length, zwidth);
+		draw_b_bone_boxes(OB_WIRE, pchan, ebone, xwidth, length, zwidth);
 	}
 }