Two in one:

- Bugfix #25937
  Child-of constraint now behaves like regular parent-child
  relationship when all options are set. This prevents the 
  errors that can happen when decomposing non-uniform matrices.

- Todo item
  The area corner hotspots for splitting/merging were far too
  narrow. Now it uses a circular distance to detect whether
  the hotspot is active. Also cleaned up drawing code for it.

1 files changed, 64 insertions, 47 deletions

diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index c61f3ba3683..e653a6198ca 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -834,54 +834,71 @@ static void childof_evaluate (bConstraint *con, bConstraintOb *cob, ListBase *ta
 	
 	/* only evaluate if there is a target */
 	if (VALID_CONS_TARGET(ct)) {
-		float parmat[4][4], invmat[4][4], tempmat[4][4];
-		float loc[3], eul[3], size[3];
-		float loco[3], eulo[3], sizo[3];
-		
-		/* get offset (parent-inverse) matrix */
-		copy_m4_m4(invmat, data->invmat);
-		
-		/* extract components of both matrices */
-		copy_v3_v3(loc, ct->matrix[3]);
-		mat4_to_eulO(eul, ct->rotOrder, ct->matrix);
-		mat4_to_size(size, ct->matrix);
-		
-		copy_v3_v3(loco, invmat[3]);
-		mat4_to_eulO(eulo, cob->rotOrder, invmat);
-		mat4_to_size(sizo, invmat);
-		
-		/* disable channels not enabled */
-		if (!(data->flag & CHILDOF_LOCX)) loc[0]= loco[0]= 0.0f;
-		if (!(data->flag & CHILDOF_LOCY)) loc[1]= loco[1]= 0.0f;
-		if (!(data->flag & CHILDOF_LOCZ)) loc[2]= loco[2]= 0.0f;
-		if (!(data->flag & CHILDOF_ROTX)) eul[0]= eulo[0]= 0.0f;
-		if (!(data->flag & CHILDOF_ROTY)) eul[1]= eulo[1]= 0.0f;
-		if (!(data->flag & CHILDOF_ROTZ)) eul[2]= eulo[2]= 0.0f;
-		if (!(data->flag & CHILDOF_SIZEX)) size[0]= sizo[0]= 1.0f;
-		if (!(data->flag & CHILDOF_SIZEY)) size[1]= sizo[1]= 1.0f;
-		if (!(data->flag & CHILDOF_SIZEZ)) size[2]= sizo[2]= 1.0f;
-		
-		/* make new target mat and offset mat */
-		loc_eulO_size_to_mat4(ct->matrix, loc, eul, size, ct->rotOrder);
-		loc_eulO_size_to_mat4(invmat, loco, eulo, sizo, cob->rotOrder);
-		
-		/* multiply target (parent matrix) by offset (parent inverse) to get 
-		 * the effect of the parent that will be exherted on the owner
-		 */
-		mul_m4_m4m4(parmat, invmat, ct->matrix);
+		float parmat[4][4];
 		
-		/* now multiply the parent matrix by the owner matrix to get the 
-		 * the effect of this constraint (i.e.  owner is 'parented' to parent)
-		 */
-		copy_m4_m4(tempmat, cob->matrix);
-		mul_m4_m4m4(cob->matrix, tempmat, parmat);
-
-		/* without this, changes to scale and rotation can change location
-		 * of a parentless bone or a disconnected bone. Even though its set
-		 * to zero above. */
-		if (!(data->flag & CHILDOF_LOCX)) cob->matrix[3][0]= tempmat[3][0];
-		if (!(data->flag & CHILDOF_LOCY)) cob->matrix[3][1]= tempmat[3][1];
-		if (!(data->flag & CHILDOF_LOCZ)) cob->matrix[3][2]= tempmat[3][2];	
+		/* simple matrix parenting */
+		if(data->flag == CHILDOF_ALL) {
+			
+			/* multiply target (parent matrix) by offset (parent inverse) to get 
+			 * the effect of the parent that will be exherted on the owner
+			 */
+			mul_m4_m4m4(parmat, data->invmat, ct->matrix);
+			
+			/* now multiply the parent matrix by the owner matrix to get the 
+			 * the effect of this constraint (i.e.  owner is 'parented' to parent)
+			 */
+			mul_m4_m4m4(cob->matrix, cob->matrix, parmat);
+		}
+		else {
+			float invmat[4][4], tempmat[4][4];
+			float loc[3], eul[3], size[3];
+			float loco[3], eulo[3], sizo[3];
+			
+			/* get offset (parent-inverse) matrix */
+			copy_m4_m4(invmat, data->invmat);
+			
+			/* extract components of both matrices */
+			copy_v3_v3(loc, ct->matrix[3]);
+			mat4_to_eulO(eul, ct->rotOrder, ct->matrix);
+			mat4_to_size(size, ct->matrix);
+			
+			copy_v3_v3(loco, invmat[3]);
+			mat4_to_eulO(eulo, cob->rotOrder, invmat);
+			mat4_to_size(sizo, invmat);
+			
+			/* disable channels not enabled */
+			if (!(data->flag & CHILDOF_LOCX)) loc[0]= loco[0]= 0.0f;
+			if (!(data->flag & CHILDOF_LOCY)) loc[1]= loco[1]= 0.0f;
+			if (!(data->flag & CHILDOF_LOCZ)) loc[2]= loco[2]= 0.0f;
+			if (!(data->flag & CHILDOF_ROTX)) eul[0]= eulo[0]= 0.0f;
+			if (!(data->flag & CHILDOF_ROTY)) eul[1]= eulo[1]= 0.0f;
+			if (!(data->flag & CHILDOF_ROTZ)) eul[2]= eulo[2]= 0.0f;
+			if (!(data->flag & CHILDOF_SIZEX)) size[0]= sizo[0]= 1.0f;
+			if (!(data->flag & CHILDOF_SIZEY)) size[1]= sizo[1]= 1.0f;
+			if (!(data->flag & CHILDOF_SIZEZ)) size[2]= sizo[2]= 1.0f;
+			
+			/* make new target mat and offset mat */
+			loc_eulO_size_to_mat4(ct->matrix, loc, eul, size, ct->rotOrder);
+			loc_eulO_size_to_mat4(invmat, loco, eulo, sizo, cob->rotOrder);
+			
+			/* multiply target (parent matrix) by offset (parent inverse) to get 
+			 * the effect of the parent that will be exherted on the owner
+			 */
+			mul_m4_m4m4(parmat, invmat, ct->matrix);
+			
+			/* now multiply the parent matrix by the owner matrix to get the 
+			 * the effect of this constraint (i.e.  owner is 'parented' to parent)
+			 */
+			copy_m4_m4(tempmat, cob->matrix);
+			mul_m4_m4m4(cob->matrix, tempmat, parmat);
+
+			/* without this, changes to scale and rotation can change location
+			 * of a parentless bone or a disconnected bone. Even though its set
+			 * to zero above. */
+			if (!(data->flag & CHILDOF_LOCX)) cob->matrix[3][0]= tempmat[3][0];
+			if (!(data->flag & CHILDOF_LOCY)) cob->matrix[3][1]= tempmat[3][1];
+			if (!(data->flag & CHILDOF_LOCZ)) cob->matrix[3][2]= tempmat[3][2];	
+		}
 	}
 }