SIGGRAPH 2021: Global Illumination Based on Surfels

This course was presented at ACM SIGGRAPH 2021. https://s2021.siggraph.org/

The SIGGRAPH presentation by Henrik Halen and Andreas Brinck presents global Illumination Based on Surfels (GIBS) – a solution for calculating indirect diffuse illumination in real-time. The solution combines hardware ray tracing with a discretization of scene geometry to cache and amortize lighting calculations across time and space. It requires no pre-computation, no special meshes, and no special UV sets, freeing artists from tedious and time-consuming processes required by traditional solutions. GIBS enables new possibilities in the runtime, allowing for high fidelity lighting in dynamic environments and for user-created content, while accommodating content of arbitrary scale. The algorithm is part of the suite of tools available to developers and teams throughout EA as part of the Frostbite engine.

This talk will detail the GIBS algorithm and how surfels are used to enable real-time ray-traced global illumination. We will describe how the scene is discretized into surfels on the fly, and why we think this discretization is a good fit for caching lighting operations. The talk will describe the acceleration structure used to enable efficient access to surfel data, and how this structure allows us to cover environments of arbitrary size, while keeping a predictable performance and memory footprint. We will detail how the algorithm handles dynamic objects, skinned characters, and transparency. Several techniques have been developed to efficiently integrate irradiance on surfels. We will describe our use of ray guiding, ray binning, spatial filters, and how we handle scenes with large numbers of lights.

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