V-Ray
From Just Solve the File Format Problem
V-Ray material files are textures used with software like Sketchup, Rhino, 3DSMax, etc. Originally developed by ASGvis, the company is now owned by Chaos Group.
File Format
Original .VISMAT format is a binary file, later versions used an XML tagging structure which is interchangeable with the .VRMAT format. Tagging begins and ends with <vismat>.
V-Ray 1.49 was last version to write to the .VISMAT format.