These folders, ranging from ground to polishedfrontpainted, each represent a finish specified by Geant4’s Unified Model for Optical Surfaces. Each folder contains macro files featuring configurations in which various surface parameters are modified to showcase specific aspects of the corresponding finish.

The parameters are adjusted to highlight the essential behavior of both the surface type and the parameter in question.

Below is an image from the Geant4 Application Developer Guide that features the various finishes and their descriptions.