A (reasonably fast) multithreaded software rasterizer implementation of OpenGL 1.3(ish).
Reasonably fast for a software rasterizer :). You'll get good framerates if you stick to 640x480 or 800x600 resolutions.
For most games it's enough to put the resulting file OpenGL32.dll right into the game directory. Games like Half Life 1, Star Trek - Elite Force I or Heavy Metal F.A.K.K.² however need some config file modifications before they use the custom OpenGL driver. For this games you have to rename the OpenGL32.dll file you just compiled to something else - like swGL.dll for example - or they will just use the OpenGL driver provided from your graphics card vendor!
Put swGL.dll into Half Life 1's gldrv directory and modify the file drvmap.txt accordingly. Then select the driver from the Options menu in Half Life 1.
Put swGL.dll into the game directory. Modify the config file inside the BaseEF / fakk directory to use the new custom OpenGL driver. To do this, add the command r_gldriver "swGL.dll".
As far as I can tell Quake 3, Star Trek Elite Force I & II, Half Life 1, Unreal, Unreal Tournament 99, Heavy Metal: F.A.K.K.², Serious Sam - The First & Second Encounter and Warcraft III work pretty well for the most part. Homeworld, Enclave and Doom 3 work okay. Blade Of Darkness isn't really playable as I haven't implemented display lists. I haven't tried other titles so far.
Have fun.