All of these matrices are multipled together before being applied to, say, a model, or a triangle, whatever. There are multiple kinds of transformations you can apply while 3d rendering, including scaling, rotation, displacement (transformation), skewing and other advanced stuff if you know how to fuck with matrices. It's kind of complicated but transformations are applied to 3d renders by matrices, which are usually 4x4 arrays. They go from the bottom of the screen up. The engine only draws vertical scanlike like thingies. What I mean is, a) it's a hack b) doesn't look all that great c) Doom did fine without it -) making stuff lower than your eyes shorter, and stuff at eye-level longer, in order to make the floor appear closer, rather than actually rotating a camera in 3D studio. What you see in Doom OTOH is actually more of a visual distortion which is applied a-posteriori, and which gives you the illusion of looking up/down: they actually compress the vertical distances in a non-linear manner, e.g.

Those engines actually have a proper geometric projection, and have a perspective that's quite natural. looks like (in software mode) with how it looks with OpenGL (which IS polygonal), or even DoomBuilder's 3D preview (that's a completely different engine). Doom's engine isn't polygonal, so you can't actually look at walls with a wall-to-floor vertical angle other than 90 degrees, nor can you face the floor or ceiling directly (case in point, compare how mouselook in ZDoom/prBoom+ etc. were perfectly aware that it would be possible to throw in a similar hack, but then decided that gameplay-wise it wouldn't add much (and they had cancelled a lot of other ideas that later appeared in Heretic, Hexen and Strife, so.)Īs for 'it can be shown easily'.not quite. Of course, it might be possible that Romero, Carmack & co. Now why they didn't do that in would be interesting to see if the infamous y-shearing hack was something which was conceived 100% by Raven's coders (not unlikely, since they also added a lot of other features later on, while id had went full-force on Quake). Same engine, less than a year of separation with Doom.

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