Real-Time Volume Caustics with Image-Based Photon Tracing

Rendering of volume caustics in participating media is often expensive, even with different acceleration approaches. Basic volume photon tracing is used to render such effects, but rather slow due to its massive quantity of photons to be traced. In this paper we present an image-based volume photon tracing method for rendering volume caustics at real-time frame rates. Motivated by multi-image based photon tracing, our technique uses multiple depth maps to accelerate the intersection test procedure, achieving a plausible and fast rendering of volume caustics. Each photon dynamically selects the depth map layer for intersection test, and the test converges to an approximate solution using image space methods in a few recursions. This allows us to compute photon distribution in participating media while avoiding massive computation on accurate intersection tests with scene geometry. We demonstrate that our technique, combined with photon splatting techniques, is able to render volume caustics caused by multiple refractions.