Comment Re:Shadow clarification (Score 5, Informative) 187
You can read the substituted implementation here:
https://github.com/TTimo/doom3.gpl/blob/master/neo/renderer/tr_stencilshadow.cpp
https://github.com/TTimo/doom3.gpl/blob/master/neo/renderer/tr_shadowbounds.cpp
I won't pretend to fully understand it but it does seem to be an implementaion of shadow volumes.