2 files changed, 34 insertions, 6 deletions

diff --git a/intern/cycles/util/util_transform.cpp b/intern/cycles/util/util_transform.cpp
index b3c6506dfa0..70ee13d96d7 100644
--- a/intern/cycles/util/util_transform.cpp
+++ b/intern/cycles/util/util_transform.cpp
@@ -246,9 +246,10 @@ static void transform_decompose(Transform *decomp, const Transform *tfm)
 	decomp->w = make_float4(scale.y.z, scale.z.x, scale.z.y, scale.z.z);
 }
 
-void transform_motion_decompose(MotionTransform *decomp, const MotionTransform *motion)
+void transform_motion_decompose(MotionTransform *decomp, const MotionTransform *motion, const Transform *mid)
 {
 	transform_decompose(&decomp->pre, &motion->pre);
+	transform_decompose(&decomp->mid, mid);
 	transform_decompose(&decomp->post, &motion->post);
 }
 
diff --git a/intern/cycles/util/util_transform.h b/intern/cycles/util/util_transform.h
index 3d6aefed56d..df525542207 100644
--- a/intern/cycles/util/util_transform.h
+++ b/intern/cycles/util/util_transform.h
@@ -41,6 +41,7 @@ typedef struct Transform {
 
 typedef struct MotionTransform {
 	Transform pre;
+	Transform mid;
 	Transform post;
 } MotionTransform;
 
@@ -383,11 +384,37 @@ __device void transform_motion_interpolate(Transform *tfm, const MotionTransform
 {
 	Transform decomp;
 
-	decomp.x = quat_interpolate(motion->pre.x, motion->post.x, t);
-	decomp.y = (1.0f - t)*motion->pre.y + t*motion->post.y;
-	decomp.z = (1.0f - t)*motion->pre.z + t*motion->post.z;
-	decomp.w = (1.0f - t)*motion->pre.w + t*motion->post.w;
+	/* 3 point bezier curve interpolation for position */
+	float3 Ppre = float4_to_float3(motion->pre.y);
+	float3 Pmid = float4_to_float3(motion->mid.y);
+	float3 Ppost = float4_to_float3(motion->post.y);
 
+	float3 Pcontrol = 2.0f*Pmid - 0.5f*(Ppre + Ppost);
+	float3 P = Ppre*t*t + Pcontrol*2.0f*t*(1.0f - t) + Ppost*(1.0f - t)*(1.0f - t);
+
+	decomp.y.x = P.x;
+	decomp.y.y = P.y;
+	decomp.y.z = P.z;
+
+	/* linear interpolation for rotation and scale */
+	if(t < 0.5f) {
+		t *= 2.0f;
+
+		decomp.x = quat_interpolate(motion->pre.x, motion->mid.x, t);
+		decomp.y.w = (1.0f - t)*motion->pre.y.w + t*motion->mid.y.w;
+		decomp.z = (1.0f - t)*motion->pre.z + t*motion->mid.z;
+		decomp.w = (1.0f - t)*motion->pre.w + t*motion->mid.w;
+	}
+	else {
+		t = (t - 0.5f)*2.0f;
+
+		decomp.x = quat_interpolate(motion->mid.x, motion->post.x, t);
+		decomp.y.w = (1.0f - t)*motion->mid.y.w + t*motion->post.y.w;
+		decomp.z = (1.0f - t)*motion->mid.z + t*motion->post.z;
+		decomp.w = (1.0f - t)*motion->mid.w + t*motion->post.w;
+	}
+
+	/* compose rotation, translation, scale into matrix */
 	transform_compose(tfm, &decomp);
 }
 
@@ -398,7 +425,7 @@ __device_inline bool operator==(const MotionTransform& A, const MotionTransform&
 	return (A.pre == B.pre && A.post == B.post);
 }
 
-void transform_motion_decompose(MotionTransform *decomp, const MotionTransform *motion);
+void transform_motion_decompose(MotionTransform *decomp, const MotionTransform *motion, const Transform *mid);
 
 #endif