Implement an Armature constraint that mimics the modifier.

The main use one can imagine for this is adding tweak controls to
parts of a model that are already deformed by multiple other major
bones. It is natural to expect such locations to deform as if the
tweaks aren't there by default; however currently there is no easy
way to make a bone follow multiple other bones.

This adds a new constraint that implements the math behind the Armature
modifier, with support for explicit weights, bone envelopes, and dual
quaternion blending. It can also access bones from multiple armatures
at the same time (mainly because it's easier to code it that way.)

This also fixes dquat_to_mat4, which wasn't used anywhere before.

Differential Revision: https://developer.blender.org/D3664

1 files changed, 11 insertions, 6 deletions

diff --git a/source/blender/blenlib/intern/math_rotation.c b/source/blender/blenlib/intern/math_rotation.c
index 29e7cf32ddc..17b395036a3 100644
--- a/source/blender/blenlib/intern/math_rotation.c
+++ b/source/blender/blenlib/intern/math_rotation.c
@@ -1872,19 +1872,24 @@ void dquat_to_mat4(float mat[4][4], const DualQuat *dq)
 
 	/* normalize */
 	len = sqrtf(dot_qtqt(q0, q0));
-	if (len != 0.0f)
-		mul_qt_fl(q0, 1.0f / len);
+	if (len != 0.0f) {
+		len = 1.0f / len;
+	}
+	mul_qt_fl(q0, len);
 
 	/* rotation */
 	quat_to_mat4(mat, q0);
 
 	/* translation */
 	t = dq->trans;
-	mat[3][0] = 2.0f * (-t[0] * q0[1] + t[1] * q0[0] - t[2] * q0[3] + t[3] * q0[2]);
-	mat[3][1] = 2.0f * (-t[0] * q0[2] + t[1] * q0[3] + t[2] * q0[0] - t[3] * q0[1]);
-	mat[3][2] = 2.0f * (-t[0] * q0[3] - t[1] * q0[2] + t[2] * q0[1] + t[3] * q0[0]);
+	mat[3][0] = 2.0f * (-t[0] * q0[1] + t[1] * q0[0] - t[2] * q0[3] + t[3] * q0[2]) * len;
+	mat[3][1] = 2.0f * (-t[0] * q0[2] + t[1] * q0[3] + t[2] * q0[0] - t[3] * q0[1]) * len;
+	mat[3][2] = 2.0f * (-t[0] * q0[3] - t[1] * q0[2] + t[2] * q0[1] + t[3] * q0[0]) * len;
 
-	/* note: this does not handle scaling */
+	/* scaling */
+	if (dq->scale_weight) {
+		mul_m4_m4m4(mat, mat, dq->scale);
+	}
 }
 
 void add_weighted_dq_dq(DualQuat *dqsum, const DualQuat *dq, float weight)