Precomputed Discrete Visibility Fields for Real-Time Ray-Traced Environment Lighting

Abstract

Rendering environment lighting using ray tracing is challenging because many rays within the hemisphere are required to be traced. In this work, we propose discrete visibility fields (DVFs), which store visibility information in a uniform grid to speed up ray-traced low-frequency environment lighting for static scenes. In the precomputation stage, we compute and store the visibility and occlusion masks at the positions of the point samples of the scene using octahedral mapping. The visibility and occlusion masks of the point samples inside a grid cell are then merged by the logical OR operation. We also store the occlusion label indicating whether more than half of the pixels are occluded in the occlusion mask of each grid cell. At runtime, we exclude the rays occluded by the geometry or visible to the environment according to the information stored in the DVF. Results show that the proposed method can significantly speed up the rendering of ray-traced environment lighting and achieve real-time frame rates without sacrificing image quality. Compared to other environment lighting rendering methods based on precomputation, our method is free of tessellation or parameterization of the meshes, and the precomputation can be finished in a short time.