GGX GTR BDRF (Generalized Trowbridge-Reitz)

Hello,

The BRDF GTR is an evolution of the Disney GGX.

fliphtml5.com/ankz/kpsk/basic

The GGX is based on Chrome and does not allow all materials to be represented correctly (see pages 22-23).

The GGX-GTR corrects this problem, its technical aspect is described (page 24-27).

BRDF is used in vray, modo and other softwares since 2015. chaos.com/blog/improvements-to-the-gtr-brdf vimeo.com/128241320

Suggestion, implement the GTR function in the cycle GGX.

Sorry for my bad English.