Code Review of Doom For the iPhone

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...)."

Comments

Classics never die

[adosch]

I remember playing Doom in the mid-90's on my friend's Gateway 2000 Pentium 100Mhz. I still play it to this day from time to time (openGL port on Linux). It's mindless, self-indulging, gory, non-challenging (now, not then!), and it's becoming one of timeless those FPS games that won't die because it's story line is simple and not drug out, you're thrown right into the mix and you can keep your objective as simple as you want: Make it to the end of the map.

Re:Classics never die

[Antiocheian]

The groundbreaking REAL 3d game was Ultima Underworld. Amazing story, great music and paced to the action (due to midi synthesis) and total 3d immersion.

Pay your respects to Looking Glass.

Re:Classics never die

[Sir_Lewk]

It added a whole new kind of depth to the gameplay. Suddenly, the game wasn't just about how well you could aim, and how well you knew the maps and where the pickups where, it also mattered how good you were at moving. It was so influencial and loved, that future quake engines made it a point to allow alternative movement styles, the pro mods (CPMA stands out in particular) enhanced and added movement tricks, and entire mods were created around completely around the concept (DeFragged). The quakes were really the perfect games for FPS fans, you could pick them up easily enough because the basics were simple and the weapons were easy to use, but there were always more ways that you could improve your gameplay. If you mastered killing people with weapons, and memorized all of the maps, you cou always find better ways around the maps with the weapons.

The concepts developed in Quake I-III helped make those games legend and have made a presence in nearly every FPS since then. Now I understand that in some gaming circles, movement tricks are look down upon, somehow seen as cheating or as degrading to other peoples gaming experiances in general. I've heard of people being banned from Modern Warfare 2 servers for being "unrealistic". More than anything, this saddens me, and signifies to me an end of an era where fun and skill were important in gaming, not misguided ideas of realism.

Re:Classics never die

[Anonymous Coward]

....and before doom, a thing that most people seem to forgot..

Re:Classics never die

[Anonymous Coward]

great music and paced to the action (due to midi synthesis)

That's a feature that's missing today. The music adapting to the action was one of the things that made X-Wing/TIE Fighter great. Not only because it enhanced the experience, but because it actually provided information as well. You knew from the music when new enemies appeared without having to look at your messages. Some games try to do this today, but they're not as well put together. They don't toss in short phrases where appropriate, they'll just fade from one track to another one completely when in "combat mode".

Re:Classics never die

[gregmac]

This is also in a game where you can get hit by a rocket and live if you have enough health. And take a few hundred bullets from a simple 'machine gun'. And jumping from a ledge 6 times your height? No problem.

If it was realistic, you'd be dead from the first

These are implementation notes, not a code review

[HisMother]

This isn't a "code review" -- it's a short monograph (with Quicktime movies!) that talks about how Id got DOOM working well on the iPhone. A "code review" is, well, a critique of code, and the style, correctness, and efficiency, thereof.
</pedant>

What's with this CoreSurface licensing restriction

[mikelieman]

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.

Now this is what really annoys me. Here are tools. Appropriate tools. But you aren't allowed to use the tools, because what you're going to use them for offends The Gods.

What was that RMS was saying again?

Re:What's with this CoreSurface licensing restrict

[slim]

What was that RMS was saying again?

Don't bring attention to RMS's pragmatism. It confuses those who prefer to think of him as a hippy.

Re:Already done

[EricWright]

There are those who read (and create the /. effect) and those who post. The intersection of those groups is vanishingly small.