Time Interval Ray Tracing for Motion Blur

We introduce a new motion blur computation method for ray tracing that provides an analytical approximation of motion blurred visibility per ray. Rather than relying on timestamped rays and Monte Carlo sampling to resolve the motion blur, we associate a time interval with rays and directly evaluate when and where each ray intersects with animated object faces. Based on our simplifications, the volume swept by each animated face is represented using a triangulation of the surface of this volume. Thus, we can resolve motion blur through ray intersections with stationary triangles, and we can use any standard ray tracing acceleration structure without modifications to account for the time dimension. Rays are intersected with these triangles to analytically determine the time interval and positions of the intersections with the moving objects. Furthermore, we explain an adaptive strategy to efficiently shade the intersection intervals. As a result, we can produce noise-free motion blur for both primary and secondary rays. We also provide a general framework for emulating various camera shutter mechanisms and an artistic modification that amplifies the visibility of moving objects for emphasizing the motion in videos or static images.