GlVIS

glVIS is a builder for OpenGL ports, developed by Jānis Legzdiņš, as a companion software for glBSP. The GL_PVS lumps it creates serve a purpose similar in a way to that of the REJECT lump, allowing the engines which use it to know which subsectors can be skipped by the renderer entirely. Only Vavoom and ZDoomGL are known to make use of GL_PVS lumps.