Abstract:
With recent advances in real-time shading techniques, we can now light physically based materials with complex area light sources. Alas, one critical challenge remains: accurate area-light shadowing. The arrival of DXR opens the door to solving this problem via ray tracing, but the correct formulation isn't obvious and there are several potential pitfalls. For instance, the most popular strategy consists of tracing rays to points randomly distributed on the light source and averaging the visibility, but we will show that this is incorrect and produces visual artifacts. Instead, we propose a definition for soft shadows that allows us to compute the correct result, along with an efficient implementation that works with existing analytic area lighting solutions. Note: this talk is an extended presentation of the paper Combining Analytic Direct Illumination and Stochastic Shadows (presented at I3D) that includes additional practical details.