Importantly, the sega saturn kind of wasn't a true 3D engine that had quads as it's primitive, but rather a stamp/sprite based system that allowed to you skew, warp, and transform those rectangular images in very powerful ways, mostly being able to reproduce 3D scenes but with certain caveats about the "polygons" that caused some limitations. One good example was that the system has no concept of UV maps. Each polygon is exactly the whole texture, linearly warped. This means you can't do, for example, environment mapping natively
https://www.youtube.com/watch?v=WDJgeuoaSvQ
