Pixel Cache Light Tracing

Abstract

In this paper, we introduce Pixel Cache Light Tracing, which is a new low-noise combination of eye-path and light-path tracing. In the first pass, eye-path vertices are distributed from the observer and stored in a hit point map analogous to progressive photon mapping. In the second pass, photons are traced from the light source and projected to the image as well as gathered by the hit point map. We combine the paths from both sampling strategies in a deterministic way without multiple importance sampling, such that the final result is consistent and free from firefly artifacts. In many practical cases, this combination leads to sharper caustics and reduced noise when compared to alternative techniques at equal time. Further, the simplicity of the path combination strategy is predestined for GPU-based implementations and requires less memory than a comparable photon mapping implementation. In addition, we provide a fast, parallel and lean hash map implementation for both photon and hit point queries.