Real-Time Rendering of Glossy Reflections Using Ray Tracing and Two-Level Radiance Caching

Estimation of glossy reflections remains a challenging topic for real-time renderers. Ray tracing is a robust solution for evaluating the specular lobe of a given BRDF; however, it is computationally expensive and introduces noise that requires filtering. Other solutions, such as light probe systems, offer to approximate the signal with little to no noise and better performance but tend to introduce additional bias in the form of overly blurred visuals. This paper introduces a novel approach to rendering reflections in real time that combines the radiance probes of an existing diffuse global illumination framework with denoised ray-traced reflections calculated at a low sampling rate. We will show how combining these two sources allows producing an efficient and high-quality estimation of glossy reflections that is suitable for real-time applications such as games.