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Code Review of Doom For the iPhone

Posted by Soulskill on from the old-dogs-new-tricks dept.

Developer Fabien Sanglard has written a code review for id Software's iPhone port of Doom. It's an interesting look into how the original 1993 game (which he also reviewed to understand its rendering process) was adapted to a modern platform. "Just like Wolfenstein 3D, Doom was rendering a screenframe pixel per pixel. The only way to do this on iPhone with an acceptable framerate would be to use CoreSurface/CoreSurface.h framework. But it is unfortunately restricted and using it would prevent distribution on the AppStore. The only solution is to use OpenGL, but this comes with a few challenges: Doom was faking 3D with a 2D map. OpenGL needs real 3D vertices. More than 3D vertices, OpenGL needs data to be sent as triangles (among other things because they are easy to rasterize). But Doom sectors were made of arbitrary forms. Doom 1993's perspective was also faked, it was actually closer to an orthogonal projection than a perspective projection. Doom was using VGA palette indexing to perform special effect (red for damage, silver for invulnerable...)."

1 of 161 comments (clear)

  1. He's wrong though by Anonymous Coward · · Score: 5, Interesting

    Doom 1993's perspective was also faked, it was actually closer to an orthogonal projection than a perspective projection

    Not remotely true; DOOM's perspective is/was perfectly correct (apart from the monsters being billboards, of course - but they were perspective-correct billboards).

    The method for achieving perspective is rather unconventional, but the maths works out the same.

    Matching up floor and ceiling in an animated view with fake perspective is basically impossible.

    [I did a port of DOOM before it was open-source, so I know a thing or two about this.]