Why are the walls in Doom fully 3D, but enemies can only be rendered as 8-directional sprites?

Question

I’ve read that enemies in Doom are rendered as sprites because of hardware limitations. But why is it that walls, stairs, etc. appear fully 3d by contrast?

[example](https://www.youtube.com/watch?v=tDmf9dgso84)

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In: Technology

Answer 1

A wall is just one polygon. A simple flat shape that is easy for computers to render.

A realistic 3D model of a monster would have thousands and thousands of polygons. Even an unrealistic model would have hundreds. So, it is much harder for computers to render, and a computer of that time wouldn’t be able to.

If you make the monster just a flat shape with the 2D image of the monter drawn on it, it is much easier to render.