Taming the Shadow Terminator
Matt Jen-Yuan Chiang, Yining Karl Li, and Brent Burley
ACM SIGGRAPH 2019 Talks. Article No. 71

The shadow terminator (a) appears harsh when using shading normals. Estevez et al. [2019] (b) softens the terminator but still appears somewhat harsh. Our modified shadowing function (c) fully softens the terminator without otherwise compromising the look.
Abstract

A longstanding problem with the use of shading normals is the discontinuity introduced into the cosine falloff where part of the hemisphere around the shading normal falls below the geometric surface. Our solution is to add a geometrically derived shadowing function that adds minimal additional shadowing while falling smoothly to zero at the terminator. Our shadowing function is simple, robust, efficient and production proven.

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Text Reference

Matt Jen-Yuan Chiang, Yining Karl Li, and Brent Burley. Taming the Shadow Terminator. ACM SIGGRAPH 2019 Talks. Article 71, Jul 2019.

Bibtex Reference

@article{Chiang2019ShadowTerminator,
    author = {Chiang, Matt Jen-Yuan and Li, Yining Karl and Burley, Brent},
    title = {Taming the Shadow Terminator},
    journal = {ACM SIGGRAPH 2019 Talks},
    month = jul,
    year = {2019},
    articleno = {71},
    doi = {10.1145/3306307.3328172},
}

Errata

In the official publisher's version, the caption for Figure 5 reads "The horizontal axis is the light angle as measured from the shading normal". The caption should read "The horizontal axis is the light angle as measured from the geometric normal". This typo is fixed in the author's version above.

Acknowledgements

We thank Peter Kutz for initial exploration into Schüssler et al. [2017], which helped motivate this project. We thank the Hyperion development team for supporting this project, the many artists at Walt Disney Animation Studios who tested this technique, the leadership of Frozen 2 for adopting this technique in production, and finally our paper reviewers for providing invaluable comments and suggestions.

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