Bugfix #7573

NLA Window, Strip blending mode "Add" didn't work at all.
It was using very bad quaternion addition. Replaced with proper code.

For devs; new is the function QuatMulFac(quat, factor) which allows to
multiply a rotation with a value (make it rotate more or less)

2 files changed, 17 insertions, 1 deletions

diff --git a/source/blender/blenlib/BLI_arithb.h b/source/blender/blenlib/BLI_arithb.h
index 9e4412d3cd3..32308f89a15 100644
--- a/source/blender/blenlib/BLI_arithb.h
+++ b/source/blender/blenlib/BLI_arithb.h
@@ -119,6 +119,8 @@ void QuatToEul(float *quat, float *eul);
 void QuatOne(float *);
 void QuatMul(float *, float *, float *);
 void QuatMulVecf(float *q, float *v);
+void QuatMulf(float *q, float f);
+void QuatMulFac(float *q, float fac);
 
 void NormalQuat(float *);
 void VecRotToQuat(float *vec, float phi, float *quat);
@@ -126,7 +128,6 @@ void VecRotToQuat(float *vec, float phi, float *quat);
 void QuatSub(float *q, float *q1, float *q2);
 void QuatConj(float *q);
 void QuatInv(float *q);
-void QuatMulf(float *q, float f);
 float QuatDot(float *q1, float *q2);
 void QuatCopy(float *q1, float *q2);
 
diff --git a/source/blender/blenlib/intern/arithb.c b/source/blender/blenlib/intern/arithb.c
index 5a37205af01..2888a684af1 100644
--- a/source/blender/blenlib/intern/arithb.c
+++ b/source/blender/blenlib/intern/arithb.c
@@ -1109,6 +1109,7 @@ void QuatInv(float *q)
 	QuatMulf(q, 1.0f/f);
 }
 
+/* simple mult */
 void QuatMulf(float *q, float f)
 {
 	q[0] *= f;
@@ -1124,6 +1125,20 @@ void QuatSub(float *q, float *q1, float *q2)
 	q2[0]= -q2[0];
 }
 
+/* angular mult factor */
+void QuatMulFac(float *q, float fac)
+{
+	float angle= fac*saacos(q[0]);	/* quat[0]= cos(0.5*angle), but now the 0.5 and 2.0 rule out */
+	
+	float co= (float)cos(angle);
+	float si= (float)sin(angle);
+	q[0]= co;
+	Normalize(q+1);
+	q[1]*= si;
+	q[2]*= si;
+	q[3]*= si;
+	
+}
 
 void QuatToMat3( float *q, float m[][3])
 {