2019, Koskela, M., Lotvonen, A., Mäkitalo, M., Kivi, P., and Jääskeläinen, P., In Proceedings of the Eurographics Symposium on Rendering.
Abstract: Computing power is still the limiting factor in photorealistic real-time rendering. Foveated rendering improves perceived quality by focusing the rendering effort on where the user is looking at. Applying foveated rendering to real-time path tracing where we must work on a very small number of samples per pixel introduces additional challenges; the rendering result is thoroughly noisy and sparse in the periphery. In this paper we demonstrate foveated real-time path tracing system and propose a novel Visual-Polar space in which both real-time path tracing and denoising is done before mapping to screen space. When path tracing a regular grid of samples in Visual-Polar space, the screen space sample distribution follows the human visual acuity model, making both the rendering and denoising 2.5× faster with similar perceived quality. In addition, when using Visual-Polar space, primary rays stay more coherent, leading to improved utilization of the GPU resources and, therefore, making ray traversal 1.3-1.5× faster. Moreover, Visual-Polar space improves 1 sample per pixel denoising quality in the fovea. We show that Visual-Polar based path tracing enables real-time rendering for contemporary virtual reality devices even without dedicated ray tracing hardware acceleration.