Comment by rufo

Voodoo 1-3 couldn’t render 32-bit color, so maybe you were noticing the lower bit depth?

3dfx did design some tricks into the video pipeline on Voodoo 2 and 3 cards that allowed for what they called 22-but color, and it definitely looked better than other 3D accelerator cards’ 16-bit modes - but it was still not as clean looking as true 32-bit color. (Interestingly, the filtering they did was applied after the framebuffer, so screen captures would only ever show the lower quality original.)