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/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;
 		}
 	}