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Global Illumination in 'Apex Legends': Smart Sampling and Spherical Harmonics

Earl Hammon (Lead Software Engineer, Respawn Entertainment)

Pass Type: All Access Pass, Core+Summits Pass, Core Pass - Get your pass now!

Topic: Programming

Format: Session

Vault Recording: TBD

Audience Level: Advanced

This talk presents an adaptive progressive sampling strategy for integrating incoming lighting over a (hemi)sphere to give the best results with the fewest samples. Unlike normal progressive sampling, future sample directions are chosen based on the results of previous samples. This achieves denser samples to outline a sharp boundary between very different regions (such as the sky and the ground), while choosing an appropriate sample density in smoothly varying regions (such as the ground itself). Subjectively, 200-400 adaptive samples tend to give results virtually indistinguishable from 2000 uniform samples.

We will briefly introduce global illumination, then develop the new sampling algorithm through several informative attempts. Finally, we'll make some observations about representing diffuse lighting in spherical harmonics that should make spherical harmonics more intuitive, especially their expressive power and their limitations.

Takeaway

Learn about integration through sampling, and discover a new sampling strategy to intelligently integrate all lighting arriving at a point. Smarter sample placement improves image quality and/or reduces execution time. Also, spherical harmonics just may become a little less mysterious...

Intended Audience

This talk is for all programmers interested in CG lighting. It has technical details useful to people highly experienced in the field, but carries you through the concepts with little prerequisite knowledge and tons of pictures, so it should still be engaging and educational to people who have interest but not experience.