Renaming opengl32.dll from QeffectsGL, as 3dfxgl.dll and viceversa (3dfxgl.dll as opengl32.dll), fooled Quake 2. In the video menu of DoD, you apply default opengl, than 3dfx opengl. Next time you gotta do it all over again (apply the video modes and QeffectsGL will work) because it is reverting to software mode. If your DoD works, under a different operating machine, don't do this. If you don't want to use QeffectsGL, OpenGL or software that belongs to the DoD mod will work.
This is 3.24, use it with Dawn of Darkness :
