Physically based shading in theory and practice
Recent Advances in Physically Based Shading Naty Hoffman This year's course introduction will follow a different approach than previous years, presenting an overview of recent advances in the theory and practice of physically based shading. Last year's introduction, Physics and Math of Shading, is available from last year's course page and is recommended background for anyone attending the course for the first time. Physically Based Hair Shading in Unreal Brian Karis The common method for shading hair in games is still based on ad hoc models. I will discuss the hair shading model we developed for Unreal Engine 4, which is being used on Paragon. To accomplish this, we gathered copious reference photography, built ground truth implementations and set about approximating a state of the art model currently used in film. I will cover how the complex calculations were approximated both for punctual light sources and image based lighting. Practical Real Time Strategies for Accurate Indirect Occlusion Jorge Jimenez, Angelo Pesce and Xian Chun Wu This talk will cover accurate screen space approaches to diffuse and specular occlusion of indirect lighting, engineered to match Monte Carlo ground truth references. For diffuse occlusion, we propose cosine weighted horizon based ambient occlusion, for which we will show its ground truth analytical derivation. Furthermore, regular ambient occlusion shows higher contrast than the occlusion observed in ground truth references, due to secondary bounces. To improve on this, we locally approximate multiple bounces of colored occlusion by fitting to ray traced references. Finally, our specular occlusion is performed by calculating the intersection of the visibility cone by the actual specular lobe, which is accurately achieved by means of a look up table. The performance of these techniques allows for practical integration into game engines. In particular, the ambient occlusion component takes 0.5ms (PS4, 1080p) and has been used successfully in production.
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