Real-Time Ray-Traced Soft Shadows of Environmental Lighting by Conical Ray Culling

Abstract

Soft shadows of environmental lighting provide important visual cues in realistic rendering. However, rendering of soft shadows of environmental lighting in real-time is difficult because evaluating the visibility function is challenging. In this work, we present a method to render soft shadows of environmental lighting at real-time frame rates based on hardware-accelerated ray tracing. We assume that the scene contains both static and dynamic objects. To composite the soft shadows cast by dynamic objects with the precomputed lighting of static objects, the incident irradiance occluded by dynamic objects, which is obtained by accumulating the occluded incident radiances over the hemisphere using ray tracing, is subtracted from the precomputed incident irradiance. Conical ray culling is proposed to exclude the rays that cannot intersect dynamic objects, which significantly improves rendering efficiency. Rendering results demonstrate that our proposed method can achieve real-time rendering of soft shadows of environmental lighting cast by dynamic objects.