This page provides information about the V-Ray Mtl OSL.
Overview
The V-Ray Mtl OSL material can be used to load OSL shader code files (.osl) or OSL object code files (.oso) and render them directly with V-Ray. The V-Ray OSL Mtl plug-in can be used with shaders that write in closure color output parameters.
Parameters
OSL Source – Specifies whether the OSL shader code is inserted internally or loaded through a file.
Internal – The OSL shader code is inserted inline.
External – The OSL shader code is loaded through a file. Paste the file directory into the field or click on the 
icon to open the File View window and select the file from there.
Max Ray Depth – Specifies the maximum reflection/refraction depth for the material.