The explanation is a great read. It reminds me of Unc's amazing explanation of how they did "cdak", possibly one of the best 4k demos ever made:
https://web.archive.org/web/20150112121832/https://www.pouet...
(for completeness, cdak pouet/download page: https://www.pouet.net/prod.php?which=55758 - youtube capture: https://www.youtube.com/watch?v=RCh3Q08HMfs)