This is a physically based shading renderer in OpenGL/GLSL. The physically based part means that the shading model tries to preserve the incoming and outgoing energy in the environment (though it is still a rough approximation).
- The PBR pipeline uses the metallic/roughness workflow.
- The BRDF uses the Cook-Torrance specular factor and Lambertian diffuse factor. GGX is used as the normal distribution function, GGX-Smith as the geometry function and the Fresnel term is approximated using Schlick.
- The shader uses both point lights and environment lighting. The environment is loaded from an HDR map courtesy of HDR labs. The implementation which runs smoothly in real time is based on Epic Games' ideas of split-sum approximation of the evaluated reflectance equation integral.
- If you're interested there's a detailed description of the maths behind the renderer in this report.
Joey de Vries (Learn OpenGL)