Real-time Rendering of Indirectly Visible Caustics

Caustics are a challenging light transport phenomenon to render in real-time, and most previous approaches have used screen-space accumulation based on the fast rasterization hardware of GPUs. This limits the position of photon collection points to first hit screen space locations, and leads to missing caustics that should be visible in a mirror's reflection. In this paper we propose an algorithm that can render caustics visible via specular bounces in real-time. The algorithm takes advantage of hardware-accelerated ray tracing support found in modern GPUs. By constructing an acceleration structure around multiple bounce view ray hit points in world space, and tracing multiple bounce light rays through the scene, we ensure caustics can be created anywhere in the scene, not just in screen space. We analyze the performance and image quality of our approach, and show that we can produce indirectly visible caustics at real-time rates.