Improving Ray Tracing Performance with Variable Rate Shading

Abstract

Hardware-accelerated ray tracing has enabled ray traced reflections for real-time applications such as games. However, the number of traced rays during each frame must be kept low to achieve expected frame rates. Therefore, techniques such as rendering the reflections at quarter resolution are used to limit the number of rays. The recent hardware features inline ray tracing, and variable rate shading (VRS) could be combined to limit the number of rays even further. This research aims to use hardware VRS to limit the number of rays while maintaining the visual quality in the final rendered image. An experiment with performance tests is performed on a rendering pipeline using different techniques to generate rays. The techniques use inline ray tracing combined with VRS and ray generation shaders. These are compared and evaluated using performance tests and the image evaluator FLIP. The results show that limiting the number of rays with hardware VRS leads to improved performance while the difference in visual quality remains comparable.