Microfacet BRDF: Theory and Implementation of Basic PBR Materials [Shaders Monthly #9]

In Episode #9 of Shaders Monthly, the Cook-Torrance microfacet BRDF is explained, which is used nowadays to implement physically-based rendering (or "PBR" for short).

In the theoretical part, we discuss a user-friendly parameterization known as Disney's "principled" BRDF or the "Metallic-Roughness-Workflow". Furthermore, we present the theory of the Cook-Torrance microfacet model and introduce its three terms: Fresnel reflectance, the normal distribution function (NDF), and the geometry term.

In the practical part, we implement the Cook-Torrance microfacet BRDF in GLSL.

Here is the code of the created shader:
GSN Composer: https://www.gsn-lib.org/index.html#pr...
C++: https://www.mathematik.uni-marburg.de...
Java: https://www.mathematik.uni-marburg.de...

Documentation for the shader plugin node of the GSN Composer:
https://gsn-lib.org/docs/nodes/Shader...

Additional lecture slides:
https://www.uni-marburg.de/en/fb12/re...

00:00 Metallic-Roughness-Workflow (Disney's "principled" BRDF)
04:45 Microfacet BRDF
07:20 Fresnel Reflectance
14:32 Normal Distribution Function (NDF)
16:18 Geometry Term
17:44 Implementation in GLSL

References:

[Cook Torrance 1981] R. L. Cook and K. E. Torrance: A reflectance model for computer graphics. TOG 1(1):7-24, Jan. 1981

[Disney 2012] Brent Burley: Physically Based Shading at Disney, SIGGRAPH 2012 Course: Practical Physically Based Shading in Film and Game Production

[Schlick 1994] Christophe Schlick: An Inexpensive BRDF Model for Physically-Based Rendering. Computer Graphics Forum, 13 (3), 233–246, 1994

[Smith 1967] B. G. Smith: Geometrical shadowing of a random rough surface. IEEE Transactions on Antennas and Propagation 15(5):668-671, Sep. 1967

[Walter et al. 2007] B. Walter, S. R. Marschner, H. Li, K. E. Torrance: Microfacet Models for Refraction through Rough Surfaces. Eurographics Symposium on Rendering, 2007.

Music: Left U Into - Otis McDonald (YouTube Audio Library)