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The Technology Behind ID's Games
orac2 writes: "The current issue of IEEE Spectrum has an article on the groundbreaking technology behind iD Software's games, from the days of Commander Keen through to Return to Castle Wolfenstein. Graphics technologies covered include the original 2-D buffer trick that made side-scrolling games on the PC feasible, as well as the more modern Raycasting and Binary Space Partition Tree techniques. Carmack is quoted extensively."
I mean, hes not only a very good programmer, he looks like a computer dork, has a phat car, and actually cares what the community thinks about his games. As was the case when there was such a backlash about fixing the bug in the engine of quake2 that produced the strafe jump, he changed it, uproar ensued, he changed it back.
Carmack embodies what every programmer and any kind of computer company should strive to be.
Carmack has embraced the platform-generic opengl, and even coded his engine to be compatible on every major os. I love you carmack, please have my love child.
I MEAN C'MON hes the one responsible for such things as the infamous railgun, and the hilarious warnings about piracy on my copied version of wolf3d, which i still play on my 386 laptop.
ARRG (offtopic)
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So close and yet so far from the world's perfect ID number
C code is C code. No new languages, techniques, or processes will ever replace an experienced architect. Crap passes through an IDE every bit as well as the good stuff.
I have a volunteer who works with me. The kid is brilliant, and has programming mojo pouring out of his eyebrows. But there are so many debugging techniques, algorythems, and habits that he doesn't have. (Yet.)
I'm not saying older in neccissarily better. Experience is the key. 20 years of experience is 20 years of experience whether you start at 7 or 27. In my case it's 7.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Basically, what I got out of this article was that John Carmack is almost single-handedly responsible for all of my non-productive time over the past 10 years. Thanks John!
Our Carmack, who art in Texas,
hallowed be thy textures.
Thy software come, thy games be done,
on my b0xen as it is at E3.
Give us this day, our daily FPS.
And forgive us our camping,
as we gun down those who camp against us.
Lead us not into a spawn site,
but just give me the damn BFG.
For the gaming market, the GeForce,
and the booth babes are yours, now and until payday.
Binary space partitioning trees proper have fallen out of use in games.
All BSP-based games now-a-days use Solid Leaf BSP trees, which are a variation of the original and have many more useful properties for games.
It is these trees and the sectors that they create that are used for determining portals.
If two sectors have the same portal then those two portals connect and can see eachother. If a portal has no pair, then it is a portal out in to infinite space and is hence a leak in your map. Assuming, of course, a map based on a single BSP tree.
Once you have portals, PVS generation is easy. And there you go, BSP and PVS.
A lot of modern research is shying away from BSP and PVS. They limit you to indoor spaces. Entirely different technology is required for outdoor scenes. And then special hacks and logic are needed to allow for seamless transitions between the indoor and outdoor worlds.
Some think that octrees with a form of occlusion culling might very well be better as they can represent both indoor and outdoor geometry without making any distinction between them. They are much harder to cull though as no handy PVS information is present and only more difficult methods exist such as Z-pyramids.
Others stick with BSP and PVS and use the one-sided portals that would normally represent leaks but instead in this case represent windows from the BSP into the terrain, and vice-versa. This combined with some extra lighting and shodow-volume information and you can have your lighting and transitioning between indoor and outdoor be seemless.
Anyway, just the ranting of a bored man at work.
Justin Dubs
I joined Softdisk in 1995, a few years after the id guys left. The company was stunned by the success of Wolfenstein and Doom, and by Duke Nukem - also born of Softdisk alumni. It was basically a subscription software company, selling a package (card games, screen savers, etc.) on disk monthly. It was a good model for the 80's.
Softdisk tried to produce a couple of games, one called Greed (later In Pursuit of Greed) which was basically a 3D Doom-clone shooter. There was some neat technology (e.g. curved surfaces), but the art was...uh, well weak. The gameplay was decent, but there were some bugs to stomp and the ship date slipped...and slipped...and slipped. It was released, but didn't live up to the hype. The game was torn to shreds in the reviews. There was a second 3D shooter - developed totally in house, though it was basically a one-man project. The lead (only) programmer left, so it was shelved.
Softdisk finally shut down its on-disk-monthly subscription software and became an ISP/web development company. It was a necessary move, but sad since the company kicked a lot of ass in the 80's with LoadStar and Big Blue Disk.
For those interested, I ran Softdisk's online download software stores on CompuServe, Prodigy, AOL while another dude took care of eWorld. We were selling Commander Keen, Dangerous Dave, and a host of other early games the id guys produced at Softdisk. Last I checked, they were still being sold (at $19.95 a pop, even).
Oh really, is that so? Hmm, where did I see that, oh right, IN THE ARTICLE.
Profiting from improvements in computer speed and memory, Carmack began working on how to draw polygons with more arbitrary shapes than Wolfenstein's trapezoids. "It was looking like [the graphics engine] wouldn't be fast enough," he recalls, "so we had to come up with a new approach....I knew that to be fast, we still had to have strictly horizontal floors and vertical walls." The answer was a technique known as binary space partitioning (BSP). Henry Fuchs, Zvi Kedem, and Bruce Naylor had popularized BSP techniques in 1980 while at Bell Labs to render 3-D models of objects on screen.
(emphasis mine)
Perhaps READING THE ARTICLE would have saved you the trouble of trying to show us how smart you are.
Everything's stolen these days. Take the FAX machine. Why that's nothing but a waffle iron with a phone attached!
</abesimpson>
Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
I was fairly pleased with how that article turned out - when I first heard about it, I dreaded seeing a trivialized simplification of the issues, but it turned out as representative as you can be in that space.
However, I really dislike discussions of the attribution of techniques to a particular programmer. Everything is derived from things before it, and I make no claims of originality. I would say that one of my talents is the ability to be aware of what sources are feeding into my work, and be able to backtrack to them. Also, there are always lots of other possible answers for any given problem that can be made to work. BSP vs sector list, Portals vs PVS vs scan line occlusion, tilted constant Z rasterization vs block subdivision vs background divides, etc. Looked at in the proper perspective, individual techniques just aren't all that important. Sometimes it sounds like "Dude, he INVENTED needle nose pliers!!!"
Heck, I somewhat deride the very concept of originality. Creativity is just synthesis without the introspection. Lots of people will catch on that and start a rant about how Id games aren't original, but they are missing the point - it is possible to set out and develop something that will be received as "original" without ever having an "original" idea spring into your mind.
The best way to get answers is to just keep working the problem, recognizing when you are stalled, and directing the search pattern. Many of the popular notions of innovation and creativity are in some ways cop-outs that keep people from being as effective as they could be. The little document I wrote about developing a part of the shadow algorithm for Doom that Nvidia has on their website was a pretty good example of my process. Don't just wait for The Right Thing to strike you - try everything you think might even be in the right direction, so you can collect clues about the nature of the problem.
John Carmack