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Carmack's Reverse is a 3D computer graphics technique for stencil shadow volumes that solves the problem of when the viewer's "eye" enters the shadow volume by tracing backwards from some point at infinity to the eye of the camera. It is named for one of its inventors, game programmer John Carmack.
According to a widely reported forum posting, Sim Dietrich may have presented the technique to the public at a developer's forum in 1999. William Bilodeau and Michael Songy filed a US patent application for the technique the same year. entitled "Method for rendering shadows using a shadow volume and a stencil buffer" issued in 2002.
Bilodeau and Songy assigned their patent ownership rights to Creative Labs. Creative Labs, in turn, granted Id Software a license to use the invention free of charge in exchange for future support of EAX technology.
Carmack independently invented the algorithm in 2000 during the development of Doom 3. He is generally given credit for it since he, unlike Bilodeau and Songy, advertised his discovery to the larger public.
References
See also
"Carmack's Reverse"