Option to correct for 3D curve twist error. example before and after.

http://www.graphicall.org/ftp/ideasman42/curve_auto_twist.png
Access next to the "3D" edit button.

details...
- open curves use the first points orientation and minimize twist for each new segment.
- cyclic curves calculate the least twist in both directions and blend between them
- AxisAngleToQuat replaced inline code.
- Notice the model on the right now has more even corners. added Vec3ToTangent to arithb.c.

2 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_arithb.h b/source/blender/blenlib/BLI_arithb.h
index 092ed00fbe5..63b351016d4 100644
--- a/source/blender/blenlib/BLI_arithb.h
+++ b/source/blender/blenlib/BLI_arithb.h
@@ -270,6 +270,7 @@ void AxisAngleToQuat(float *q, float *axis, float angle);
 void RotationBetweenVectorsToQuat(float *q, float v1[3], float v2[3]);
 void vectoquat(float *vec, short axis, short upflag, float *q);
 
+void Vec3ToTangent(float *v, float *v1, float *v2, float *v3);
 float VecAngle2(float *v1, float *v2);
 float VecAngle3(float *v1, float *v2, float *v3);
 float NormalizedVecAngle2(float *v1, float *v2);
diff --git a/source/blender/blenlib/intern/arithb.c b/source/blender/blenlib/intern/arithb.c
index ad1dc1ca12c..970d8f7d0de 100644
--- a/source/blender/blenlib/intern/arithb.c
+++ b/source/blender/blenlib/intern/arithb.c
@@ -2969,6 +2969,19 @@ void VecRotToQuat( float *vec, float phi, float *quat)
 	}
 }
 
+/* get a direction from 3 vectors that wont depend
+ * on the distance between the points */
+void Vec3ToTangent(float *v, float *v1, float *v2, float *v3)
+{
+	float d_12[3], d_23[3];
+	VecSubf(d_12, v2, v1);
+	VecSubf(d_23, v3, v2);
+	Normalize(d_12);
+	Normalize(d_23);
+	VecAddf(v, d_12, d_23);
+	Normalize(v);
+}
+
 /* Return the angle in degrees between vecs 1-2 and 2-3 in degrees
    If v1 is a shoulder, v2 is the elbow and v3 is the hand,
    this would return the angle at the elbow */