You may be thinking of UT99 or even the first Unreal. UT2k4 required a GPU and didn't have a software renderer.
UT2k4 had software rending support via the Pixomatic software renderer from RAD Game Tools:
https://www.radgametools.com/pixo/PixoWithUnreal2004.txt
Further discussion about it here:
https://forums.beyondunreal.com/threads/software-rendering-i...
alt Hacker News
UT2k4 had software rending support via the Pixomatic software renderer from RAD Game Tools:
https://www.radgametools.com/pixo/PixoWithUnreal2004.txt
Further discussion about it here:
https://forums.beyondunreal.com/threads/software-rendering-i...