Forgot your password?
typodupeerror
First Person Shooters (Games) Programming Games

Code Review of Doom For the iPhone 161

Posted by Soulskill
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...)."
This discussion has been archived. No new comments can be posted.

Code Review of Doom For the iPhone

Comments Filter:
  • Pushing pixels (Score:5, Interesting)

    by MtHuurne (602934) on Thursday February 04, 2010 @08:09AM (#31020820) Homepage
    Forgive my ignorance, but couldn't you have the original software renderer write to an in-memory buffer and then upload that using glTexSubImage2D()?
    • Re: (Score:2, Funny)

      by pananza (1228694)
      Nah, too easy and direct approach.
    • Re: (Score:3, Interesting)

      by Lord Pillage (815466)
      Or glWritePixels() would work too. Might be a little bit closer to the original method. But then again, I didn't RTFA, so I wouldn't know.
      • Re:Pushing pixels (Score:5, Interesting)

        by RedK (112790) on Thursday February 04, 2010 @08:30AM (#31020940)
        glDrawPixels is not supported under OpenGL ES which is what the iPhone uses. An in-memory buffer used as a texture is about the only way for fullscreen images (vertex arrays drawn using GL_POINTS is another solution but would not be fast enough).
    • by egomaniac (105476)

      You'd be lucky to get 1fps doing that. Not only is iPhone texture upload horrendously slow, but glTexSubImage2D reprocesses the entire texture even if you just change a single pixel of it. Plus you need power-of-2 textures, so you're looking at a 512x512 texture upload every frame. Not going to happen. /iPhone game developer

      • by MtHuurne (602934)
        It would be used to upload the entire frame at once. And while the texture itself must have power-of-2 sizes, the updated rectangle is not restricted in that way. It is certainly possible that it won't get decent frame rates on the iPhone, but it works fine on desktops, even ones with a weak GPU.
  • Classics never die (Score:5, Insightful)

    by adosch (1397357) on Thursday February 04, 2010 @08:13AM (#31020846)
    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.
    • by goldaryn (834427) on Thursday February 04, 2010 @08:28AM (#31020932) Homepage

      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,

      In my opinion, DOOM was a good game but it wasn't ground breaking in the same way that Quake was a few years later. It was the first FPS to do real 3D, and gave birth to real FPS competitive play, based on the groundwork that DOOM did with FPS LAN play. Aside from that, the Quake engine led to all sorts of interesting gamemodes and mods that live with us still (Team Fortress was originally a Quake mod), and the physics of Quake 1 still has a legacy today (rocket jumping, bunny hopping).

      I think the insurgence of DOOM ports to phones is because the pseudo 3D interface of DOOM lends itself more to the controls of mobile devices. It'd be nice to see more Quake and Duke3D ports.

      • by Hadlock (143607) on Thursday February 04, 2010 @08:32AM (#31020950) Homepage Journal

        DOOM was a good game but it wasn't ground breaking in the same way that Quake was a few years later. It was the first FPS to do real 3D, and gave birth to real FPS competitive play, based on the groundwork that DOOM did with FPS LAN play. Aside from that, the Quake engine led to all sorts of interesting gamemodes and mods that live with us still (Team Fortress was originally a Quake mod), and the physics of Quake 1 still has a legacy today (rocket jumping, bunny hopping).

        You sir, have a career in video game blogging! Let me sign you up for a 3000 word "Top 10 Groundbreaking games of the 1990s" blog entry.

      • Re: (Score:3, Interesting)

        by goldaryn (834427)

        Aside from that, the Quake engine led to all sorts of interesting gamemodes and mods that live with us still

        I forgot to say: Action Quake was another Quake 1 mod, which eventually became Counter Strike.

        • Re: (Score:2, Interesting)

          by jaggeh (1485669)

          It was S.E.A.L. Quake not Action Quake

          Although my favorite quake mod was malice.

      • by Rhaban (987410)

        the physics of Quake 1 still has a legacy today (rocket jumping, bunny hopping).

        And how is that a good thing exactly?

        • Re: (Score:3, Insightful)

          by Sir_Lewk (967686)

          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 r

        • by Toonol (1057698)
          the physics of Quake 1 still has a legacy today (rocket jumping, bunny hopping).

          And how is that a good thing exactly?

          I agree; those are both ridiculous gameplay elements. I've always thought it was amusing that FPS players, arguably the cutting edge of photorealistic video game graphics and game physics, don't see a problem with characters behaving like a Loony Tunes cartoon.

          A jump should take you no more than eighteen inches in the air, and totally ruin your aim during and for a few moments aft
          • by gregmac (629064) on Thursday February 04, 2010 @06:04PM (#31027648) Homepage

            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

            • Also, you're much better off going for the insta CQC knife kill than pulling out a pistol in any video game. You know, because knife fights are quick and clean, but handguns take forever.

      • by Antiocheian (859870) on Thursday February 04, 2010 @09:28AM (#31021334) Journal

        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: (Score:2, Insightful)

          by Anonymous Coward
          ....and before doom, a thing that most people seem to forgot..
        • Before any of that, Elite for Acorn BBC Micro. First 3D game, and also used triangles for shapes. Now that is ground breaking.

        • I was just thinking about that, it looked so amazing for it's time. It pipped DOOM to the post by over a year and a half! Not a bad effort, a dungeon crawling RPG, in 3d, using the familar pots of health and mana as a visual - now commonly stolen.

        • I've heard many good things about this game and have wondered why no one has ever ported it to a console. Wait a minute...checking wikipedia... it WAS ported to the PSone, but only in Japan, darn it! Too bad the early Elder Scrolls games were never ported either.

        • I did neither like fantasy, nor role playing games.

          But you are right: Looking Glass was THE studio, back then.

          I love cyberpunk, horror, and sci-fi stuff. So for me it was their System Shock, that won all trophies.
          Single. Best. Game. Of. All. Time.

      • by kerrbear (163235)
        Marathon was better :-)
        • by stjobe (78285)

          Back under your rock, Apple boy!

          (just kidding, I was dead envious at my Mac-owning friends when I saw Marathon for the first time)

      • by molo (94384)

        Doom and Quake were groundbreaking in different regards. Doom was the first popular multiplayer FPS (LAN games). Quake was the first popular fully-3D FPS, and also provided the ability to play games over IP..

        Also, as far as bunnyhopping, that is an artifact introduced in the QuakeWorld engine with its predictive networking model. In classic NetQuake (the original IP quake protocol), bunnyhopping had no effect.

        -molo

        • Also, as far as bunnyhopping, that is an artifact introduced in the QuakeWorld engine with its predictive networking model. In classic NetQuake (the original IP quake protocol), bunnyhopping had no effect.

          That doesn't make sense. The prediction is done by the client, and it is not authoritative, only a guess. You might be thinking one mod vs. another, or maybe the client side prediction enabled you to time a rocket jump properly because it is hard as sh*t to do on a modem with 300ms latency and no client side tricks.

      • by kalirion (728907)

        It was the first FPS to do real 3D

        Nope, it wasn't. Descent and Terminator: Future Shock both came earlier. Probably some other stuff too.

        I'll grant you that GLQuake was most likely the first FPS to do accelerated 3D.

      • I think System Shock, which came out in the same year as Doom, kicked Doom’s ass!
        It’s weird that the whole world seems to remember Doom.
        System Shock was a wonderful piece of very creepy art. And it will always be one of the best games ever made.

    • Re: (Score:3, Funny)

      by imakemusic (1164993)

      it's story line is simple and not drug out

      Unlike, say, Pacman in which the main character spends the entire game eating pills.

      I think the word you're looking for is 'dragged'.

    • by Jesus_666 (702802)
      Take a look at Marathon. It's what Bungie did on the Mac while id released Doom for the IBM. Essentially Doom with fewer weapons, alt-fire and funny monologues. Durandal still ranks high in my list of the best insane AIs. The story is more complex than that of Doom but fairly simple to follow. Well, until you get to the third - pardon - infinitieth part, which is a time travel bonanza full of alternate pasts you never get to see.

      The engine used for Marathon 2 and Infinity is available as Aleph One; the fi
      • by anss123 (985305)
        I tried Aleph One but I thought it was rather boring. Felt like they took the library level of Halo and stretched it out into a full game.

        Mind you I think Wolf3D and Quake SP is boring too so my gaming taste isn't exactly mainstream.
        • by Jesus_666 (702802)
          The terminals saved the game for me. The gameplay isn't the most inspiring but the writing is great. Still didn't pull me all the way through Marathon 2, though.
    • by Hatta (162192)

      I remember playing Doom in the mid-90's on my friend's Gateway 2000 Pentium 100Mhz.

      And that was way over powered for Doom. I played Half-life for the first time (all the way through) on a P133. Yeah it sucked, but not as much as not playing Half-Life. Doom was certainly playable with a 386, and a 486 was more than enough. These days I can even play Doom on my Sansa C250 with Rockbox, and my printer has a faster processor than the computer I first played Half-Life on.

      • by mzs (595629)

        Hmmm... Doom was okay on a 33MHz 486DX with 128KB of ecache for single player (stayed above 15 FPS), but for network death match with DEC tulip based ISA NICs using thin coax it would lag and play at 10-12 FPS on that box. The 50MHz 486DX2 and 75MHz 486DX4 did okay. Also there was a 40MHz 386 with a 3COM NIC ISA card that could hold it's own, it did have a Paradise 16-bit ISA SVGA card, the others were Trident and Cirrus Logic, and it did not lag but the frame rate was in the 10-12 FPS range too in deathmat

    • by CAIMLAS (41445)

      Meh. Your friend had a P100?

      I remember playing it on a friend's parents' 386 DX, which we had covertly over-clocked to something like 44MHz.

      Kids these days, they get everything...

  • Bloody Hell (Score:2, Funny)

    by Anonymous Coward

    I thought it was "Code Review of Doom" for the iPhone not "Code Review" of "Doom for the iPhone".
    I've seen some "code reviews of doom". I was looking forward to some juicy ApplePain.
    Oh well.

    • by theJML (911853)

      I read it the same way. I thought perhaps they were reviewing the source code for the OS or something and then I find "Doom"... which being an interesting game, isn't as great as reviewing the source code to the iPhone OS would be.

  • He's wrong though (Score:5, Interesting)

    by Anonymous Coward on Thursday February 04, 2010 @08:33AM (#31020956)

    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.]

    • Re:He's wrong though (Score:5, Informative)

      by Anonymous Coward on Thursday February 04, 2010 @09:08AM (#31021164)

      You are correct. What TFA probably means is that walls, floors and ceilings are drawn in strips, and that for every strip all the texels are looked up according to a straight line. But that doesn't mean at all that hence Doom just uses an orthogonal projection, since it actually let's things diminish in the distance properly. A lot of real three dimensional games actually linearised texel lookup, but that says nothing at all about the overall projection a game uses. If you want to know what an orthogonal projection looks like, go play Age of Empires. As an added comparison, take a look at Mode 7 tricks on the SNES. You can actually perspectively correctly display a flat surface on it. How is this done? By setting a different orthogonal projection for each (in this case horizontal) line. That does not mean however that games using this therefore use an orthogonal projection, because the parameters are different for each scanline and the overall projection is perspective.

    • In a true perspective view different parts of a wall vertex will be different distances from your viewpoint, therefore they will not be a straight vertical line. In the psuedo perspective that doom and duke used a wall vertex is always a straight vertical line.

      This is more noticable in duke than in doom because duke lets you move your view up and down and therefore see angles further from the vertical than doom does.

    • by dpilot (134227)

      Go try Heretic or Hexen - the originals based on Doom, and then make your call. Doom restricted things so you couldn't look up or down, and simplified the perspective issue. Heretic (followed by Hexen) added the ability to look up and down, and showed pretty bad perspective distortion.

  • by drinkypoo (153816) <martin.espinoza@gmail.com> on Thursday February 04, 2010 @08:35AM (#31020972) Homepage Journal

    But it won't fit on a 800 pixel wide screen. WTF? I thought it was a code review, not a flash game.

  • by HisMother (413313) on Thursday February 04, 2010 @08:57AM (#31021094)
    <pedant>
    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>
  • by mikelieman (35628) on Thursday February 04, 2010 @08:58AM (#31021114) Homepage

    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?

  • Heh, I remember playing Doom in my uncle's computer back in 94 as as 9 year old boy, and loved it, adored it.

    16 years later, now an employed programmer, I still think it is made of black sorcery and an ingenious amount of coding. That's awesome!

    Does Carmack /id Soft have a donation paypal-esque account? I'd love to give them what is due for all those early years of pure fun.

    • Does Carmack /id Soft have a donation paypal-esque account? I'd love to give them what is due for all those early years of pure fun.

      How about just buying one of their more recent games?

    • Just buy their games. Go buy some copies of doom, quake or Doom 3 or wait for RAGE and buy a bunch of those.

    • Re: (Score:3, Informative)

      You can still buy id classics on e.g. Steam.

  • The Sony Ericson P800 and the Motorola A920 had Doom ports that were very true to the Doom experience... in 2003.

    As an unlocked A920 user, there is very little on the iPhone that I didn't see on that device. Apple's real accomplishment has been wrestling control away from the carriers who {locked down/disabled/walled gardened/made crappy} all of the devices that they sold.

    I am happy for what Apple has done. It has allowed me to buy a Motorola Droid from Verizon without all of the restrictions it would other

  • by asylumx (881307) on Thursday February 04, 2010 @01:04PM (#31023880)
    I think this is how I'll start referring to ALL my code reviews ;-)
  • Jump using accelerometer!

    Just like the unintentional Nintendo and Mario Bros. Which they should seriously do by the way!

  • That's a fine hack, well done old chap.

  • by Anonymous Coward on Thursday February 04, 2010 @01:55PM (#31024582)

    A long time ago, I ported Quake 3 to windows mobile. Tedious, but it worked reasonably at around 30fps (and deathmatch worked) with OpenGLES acceleration on the Dell Axim x50v enabled with the intel 2700g coprocessor. The code is still out there, but frankly, it wouldn't be kosher for me to push a copy of Quake 3 to the iphone store since i dont have copyright access to the 'assets' of the game and i dont need to get sued or something.

    it's a bit useless to gpl your game and not the assets. If iD software wants to use the code for a quake 3 for iphone, they can do so at http://code.google.com/p/q3ce/source/checkout. Should save them some time. Open invite, go right ahead, i can't do anything with it these days anyway.

    (and yes, i converted the whole thing from floating point to fixed point using some fun c++ templates, poke around the code to see how it works, it's kinda neat.)

Never invest your money in anything that eats or needs repainting. -- Billy Rose

Working...