Took a quick look at fatmap2 and surprisingly it doesn't do perspective-correct texture mapping (although it points to some other document in the introduction).
Edit: it was actually possible at the time.
This worked well enough if the triangle was seen fairly straight on and was not too large.
Quake popularized the per-8 pixels technique, which is close enough in most cases.
This one[1], code being here[2]?
> surprisingly it doesn't do perspective-correct texture mapping
Yeah it was covered in some other document, can't recall which. I have some memory of fatmap3, but I can't find any references to it, and any files I had were on my IBM Deathstar[3]...
[1]: https://www.gamers.org/dEngine/rsc/
[2]: https://www.gamers.org/dEngine/rsc/3dgpl/code/
[3]: https://en.wikipedia.org/wiki/Deskstar#IBM_Deskstar_75GXP_fa...