Models of light reflection for computer synthesized pictures
@inproceedings{blinn1977models,
title={Models of light reflection for computer synthesized pictures},
author={Blinn, James F},
booktitle={Proceedings of the 4th annual conference on Computer graphics and interactive techniques},
pages={192--198},
year={1977}
}
Using Microfacets fo model percentage sirface differentials with normal equal to a given halfway vector (vector between light and viewer).