Lynne Shapiro Brotman, Norman I. Badler. Generating soft shadows with a depth buffer algorithm. IEEE Computer Graphics and Applications, 4(10):5-14, 1984. [doi]
@article{BrotmanB84,
title = {Generating soft shadows with a depth buffer algorithm},
author = {Lynne Shapiro Brotman and Norman I. Badler},
year = {1984},
doi = {10.1109/MCG.1984.6429330},
url = {http://dx.doi.org/10.1109/MCG.1984.6429330},
researchr = {https://researchr.org/publication/BrotmanB84},
cites = {0},
citedby = {0},
journal = {IEEE Computer Graphics and Applications},
volume = {4},
number = {10},
pages = {5-14},
}