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Kilgard, Mark; John Carmack. "John Carmack on shadow volumes..."Practical and Robust Shadow Volumes page of NVIDIA Developer Zone. archive.org: NVIDIA. Archived from the original on January 27, 2009. Retrieved 18 October 2012.
Kilgard, Mark; John Carmack. "John Carmack on shadow volumes..."Practical and Robust Shadow Volumes page of NVIDIA Developer Zone. archive.org: NVIDIA. Archived from the original on January 27, 2009. Retrieved 18 October 2012.