本文探讨了物理基底着色（PBR）中GGX、Smith/GGX等模型的应用，并对比了不同几何遮挡及正常分布函数的效果。作者偏好Schlick近似用于Fresnel效应，同时介绍了几种混合采样技术。
Physically Based Shading and Image Based Lighting 9
http://www.trentreed.net/blog/physically-based-shading-and-image-based-lighting/
This factor is very unfortunately named. The reason why is because it’s often confused with regular, mathematic Normal Distributions (like what we used to blur Exponential Shadow Maps in the previous blog post). However, the name is appropriate.
Generally GGX, or some mixture of Smith/GGX is very popular. I tend to like different ones depending on the scene and light composition. I stick with Schlick’s Approximation for Fresnel. For Geometry Occlusion I prefer either Smith/Ggx, Smith-Schlick-Beckmann, or Cook-Torrance. And for Normal Distribution, Ggx has a longer specular tail – I tend to prefer that. For Importance-Sampling, I tend to mix and match (even though mathematically this is incorrect) by using Beckmann sampling with Ggx Normal Distribution. But you can see how the terms work together to produce pretty impressive results.
References
Note: Links with an asterisk (*) by them indicate a source that was integral in my understanding in Physically Based Shading. I highly recommend these sources.
Any of the wonderful Siggraph courses (2012, 2013, 2014)
*Physics and Math of Shading (Naty Hoffman)
*Understanding the Shadow Masking Function (Eric Heitz)
Moving Frostbite to PBR (Sébas1en Lagarde, Charles de Rousiers)
Real Shading in Unreal Engine 4 (Brian Karis) [Slides]
Crafting a Next-Gen Material Pipeline for The Order: 1886 (David Neubelt, Matt Pettineo)
*Microfacet Models for Refraction through Rough Surfaces (Bruce Walter, Stephen Marschner, Hongsong Li, Kenneth Torrance)
Physically-Based Shading at Disney (Brent Burley)
http://www.trentreed.net/blog/physically-based-shading-and-image-based-lighting/
This factor is very unfortunately named. The reason why is because it’s often confused with regular, mathematic Normal Distributions (like what we used to blur Exponential Shadow Maps in the previous blog post). However, the name is appropriate.
Generally GGX, or some mixture of Smith/GGX is very popular. I tend to like different ones depending on the scene and light composition. I stick with Schlick’s Approximation for Fresnel. For Geometry Occlusion I prefer either Smith/Ggx, Smith-Schlick-Beckmann, or Cook-Torrance. And for Normal Distribution, Ggx has a longer specular tail – I tend to prefer that. For Importance-Sampling, I tend to mix and match (even though mathematically this is incorrect) by using Beckmann sampling with Ggx Normal Distribution. But you can see how the terms work together to produce pretty impressive results.
References
Note: Links with an asterisk (*) by them indicate a source that was integral in my understanding in Physically Based Shading. I highly recommend these sources.
Any of the wonderful Siggraph courses (2012, 2013, 2014)
*Physics and Math of Shading (Naty Hoffman)
*Understanding the Shadow Masking Function (Eric Heitz)
Moving Frostbite to PBR (Sébas1en Lagarde, Charles de Rousiers)
Real Shading in Unreal Engine 4 (Brian Karis) [Slides]
Crafting a Next-Gen Material Pipeline for The Order: 1886 (David Neubelt, Matt Pettineo)
*Microfacet Models for Refraction through Rough Surfaces (Bruce Walter, Stephen Marschner, Hongsong Li, Kenneth Torrance)
Physically-Based Shading at Disney (Brent Burley)
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