This paper describes the work we did to derive calculations of the Smith shadowing function for different values of the highlight tail falloff of the GTR BRDF in V-Ray 3.20. See below for the PDF and source code.

(Open in new tab or Save as... the image below to see the full 4096x4096 resolution.)

 

 

Link to PDF: gtr_shadowing.pdf

Link to C++ source code snippet: gtr_shadowing_code.zip

The Mathematica notebooks: G1.nb and G1_1.nb