Cycles: motion blur is now curved and passes exactly through the midpoint.

Previously it would only interpolate between the previous and next frame,
which meant it might not hit the current frame position.

intern/cycles/kernel/kernel_object.h

@@ -23,8 +23,9 @@ enum ObjectTransform {
 	OBJECT_INVERSE_TRANSFORM = 3,
 	OBJECT_PROPERTIES = 6,
 	OBJECT_TRANSFORM_MOTION_PRE = 8,
-	OBJECT_TRANSFORM_MOTION_POST = 12,
+	OBJECT_TRANSFORM_MOTION_MID = 12,
-	OBJECT_DUPLI = 16
+	OBJECT_TRANSFORM_MOTION_POST = 16,
+	OBJECT_DUPLI = 18
 };
 
 __device_inline Transform object_fetch_transform(KernelGlobals *kg, int object, enum ObjectTransform type)
@@ -59,11 +60,15 @@ __device_inline Transform object_fetch_transform_motion(KernelGlobals *kg, int o
 		motion.pre.z = kernel_tex_fetch(__objects, offset + 2);
 		motion.pre.w = kernel_tex_fetch(__objects, offset + 3);
 
+		motion.mid.x = kernel_tex_fetch(__objects, offset + 4);
+		motion.mid.y = kernel_tex_fetch(__objects, offset + 5);
+		motion.mid.z = kernel_tex_fetch(__objects, offset + 6);
+		motion.mid.w = kernel_tex_fetch(__objects, offset + 7);
 
-		motion.post.x = kernel_tex_fetch(__objects, offset + 4);
+		motion.post.x = kernel_tex_fetch(__objects, offset + 8);
-		motion.post.y = kernel_tex_fetch(__objects, offset + 5);
+		motion.post.y = kernel_tex_fetch(__objects, offset + 9);
-		motion.post.z = kernel_tex_fetch(__objects, offset + 6);
+		motion.post.z = kernel_tex_fetch(__objects, offset + 10);
-		motion.post.w = kernel_tex_fetch(__objects, offset + 7);
+		motion.post.w = kernel_tex_fetch(__objects, offset + 11);
 
 		transform_motion_interpolate(&tfm, &motion, time);
 

intern/cycles/kernel/kernel_types.h

@@ -29,7 +29,7 @@
 CCL_NAMESPACE_BEGIN
 
 /* constants */
-#define OBJECT_SIZE 		18
+#define OBJECT_SIZE 		22
 #define LIGHT_SIZE			4
 #define FILTER_TABLE_SIZE	256
 #define RAMP_TABLE_SIZE		256

intern/cycles/render/camera.cpp

@@ -197,9 +197,8 @@ void Camera::device_update(Device *device, DeviceScene *dscene, Scene *scene)
 	}
 #ifdef __CAMERA_MOTION__
 	else if(need_motion == Scene::MOTION_BLUR) {
-		/* todo: exact camera position will not be hit this way */
 		if(use_motion) {
-			transform_motion_decompose(&kcam->motion, &motion);
+			transform_motion_decompose(&kcam->motion, &motion, &matrix);
 			kcam->have_motion = 1;
 		}
 	}

intern/cycles/render/nodes.cpp

@@ -1254,8 +1254,6 @@ void WardBsdfNode::attributes(AttributeRequestSet *attributes)
 
 void WardBsdfNode::compile(SVMCompiler& compiler)
 {
-	ShaderInput *tangent_in = input("Tangent");
-
 	BsdfNode::compile(compiler, input("Roughness U"), input("Roughness V"));
 }
 

intern/cycles/render/object.cpp

@@ -57,7 +57,7 @@ void Object::compute_bounds(bool motion_blur)
 
 	if(motion_blur && use_motion) {
 		MotionTransform decomp;
-		transform_motion_decompose(&decomp, &motion);
+		transform_motion_decompose(&decomp, &motion, &tfm);
 
 		bounds = BoundBox::empty;
 
@@ -219,7 +219,7 @@ void ObjectManager::device_update_transforms(Device *device, DeviceScene *dscene
 				mtfm_post = mtfm_post * itfm;
 
 			memcpy(&objects[offset+8], &mtfm_pre, sizeof(float4)*4);
-			memcpy(&objects[offset+12], &mtfm_post, sizeof(float4)*4);
+			memcpy(&objects[offset+16], &mtfm_post, sizeof(float4)*4);
 		}
 #ifdef __OBJECT_MOTION__
 		else if(need_motion == Scene::MOTION_BLUR) {
@@ -227,21 +227,21 @@ void ObjectManager::device_update_transforms(Device *device, DeviceScene *dscene
 				/* decompose transformations for interpolation */
 				MotionTransform decomp;
 
-				transform_motion_decompose(&decomp, &ob->motion);
+				transform_motion_decompose(&decomp, &ob->motion, &ob->tfm);
-				memcpy(&objects[offset+8], &decomp, sizeof(float4)*8);
+				memcpy(&objects[offset+8], &decomp, sizeof(float4)*12);
 				flag |= SD_OBJECT_MOTION;
 				have_motion = true;
 			}
 			else {
 				float4 no_motion = make_float4(FLT_MAX);
-				memcpy(&objects[offset+8], &no_motion, sizeof(float4));
+				memcpy(&objects[offset+8], &no_motion, sizeof(float4)*12);
 			}
 		}
 #endif
 
 		/* dupli object coords */
-		objects[offset+16] = make_float4(ob->dupli_generated[0], ob->dupli_generated[1], ob->dupli_generated[2], 0.0f);
+		objects[offset+20] = make_float4(ob->dupli_generated[0], ob->dupli_generated[1], ob->dupli_generated[2], 0.0f);
-		objects[offset+17] = make_float4(ob->dupli_uv[0], ob->dupli_uv[1], 0.0f, 0.0f);
+		objects[offset+21] = make_float4(ob->dupli_uv[0], ob->dupli_uv[1], 0.0f, 0.0f);
 
 		/* object flag */
 		if(ob->use_holdout)

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);
 }
 

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);
+	/* 3 point bezier curve interpolation for position */
-	decomp.y = (1.0f - t)*motion->pre.y + t*motion->post.y;
+	float3 Ppre = float4_to_float3(motion->pre.y);
-	decomp.z = (1.0f - t)*motion->pre.z + t*motion->post.z;
+	float3 Pmid = float4_to_float3(motion->mid.y);
-	decomp.w = (1.0f - t)*motion->pre.w + t*motion->post.w;
+	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