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What is Happening with OpenGL?
Trapped In Windows Hell asks: "I was just at the local game store looking for a new game, and I noticed the absolute lack of ANYTHING other than DirectX games. Where has OpenGL gone, and what does this mean for games on GNU/Linux? If DirectX is so hard to program in, so clunky to use, and limits the game to being sold on only one OS, WHY do so many programmers use it? It seems logical (to me, at least) that programming as portably as possible, as simply as possible, and using standards where possible, leaves a lot more sales options open for the future... and DirectX seems to close all options *but one*." OpenGL use in Windows gaming has decreased dramatically in favor of the use of DirectX which is improving with each release. Will OpenGL continue to mature on the Windows platform (which arguably is the platform that drives most of the mainstream demand for graphics) or will it continue to stagnate as game and driver developers concentrate on the offerings from Microsoft?
Kudos to Cliff for not just taking the anti-MS-at-all-costs FUD from the questioner as gospel. DirectX improves a LOT with each release. DX3, or even 5, was a nightmare, but DX8 is pretty easy to use.
The more significant reason is driver quality (from the hardware company), and the 3D-graphic card industry is so cutt-throat that even a momentary falter into, admittedly, a non-mainstream-for-games OS like Linux can be fatal. Of course, they COULD release enough specs to allow OS drivers... but there are trade-secret issues there (with actual hardware, that don't apply, in my mind, to software).
How well is OpenGL supported by the video card drivers? If it is slower or buggier then DirectX then people won't be so thrilled to use it. Remember non windows boxes are less then 10% of the market (Apple had 5% at the start of the year, I doubt Apple+Apple's growth+Linux+BSDs can top 10% -- if the PS2 or GameCube use OpenGL my 10% guess is wrong though).
Plus DirectX handles input, and some non-graphical output. And I think sound. As far as I know OpenGL only does drawing.
OpenGL is what Apple recommends using for 3D game on their platform (at least under OS X), but they have their own APIs for sound and input, and hopefully force feedback (and one would hope that to the extent that DirectX "got it right" Apple copied it). So OpenGL isn't dead, unfonturely it give MS an even bigger reason to fight it.
OpenGL 1.3 closes the gap quite a bit, but DirectX 8 still has a higher featureset and will gain more features sooner than OpenGL will.
Game programmers don't give a rat's ass about portability. All it has to do is run on their target platform at an acceptable speed.Just an observation here. I was in South Africa last year, working with some companies in the simulation/training market. Most of them are developing their apps for DirectX--OpenGL was not used much at all. When I asked why, I was told that the reason is that DirectX apps will run reliably on cheap Windows boxes, which is what they're using; OpenGL is seen as something running on high-end UNIX machines. I wonder how widespread this viewpoint is?
Some companies are doing things for linux gamers. Bioware is releasing Neverwinter Nights, which could arguably be the best rpg ever released, is going to be released for linux as well as windows, and most likely it will use opengl(is there another graphics api that does 3d in linux?). Nvidia is giving full OpenGL support in their chipsets. And let's not forget the guys at ID love opengl as well. Even if their numbers are few, there are people who still want to keep OpenGL alive, and they are pretty big names is the gaming industry.
Got Freedom?
Thinking?
Now try to make a 3d engine with the features of Alice or Anarchy Online in OpenGL with OpenGL.
Erm, Alice uses the Quake 3 engine, which is certainly using OpenGL.
Bioware's next game, Neverwinter Nights, will use OpenGL for cross platform compatability. (They will ship for Windoze, Mac, Linux, and BeOS, and all on the same CD to boot!) If the game is a success (and averyone expects it to be), then maybe this might turn a few heads in the gaming industry, and a more serious look at cross-platform gaming (and thus using OpenGL) might happen.....
Ummm, almost everything in OpenGL is the same for different cards, and for different platforms. This is a huge advantage of OpenGL.
However, when a graphic chip company creates a new functionality, it usually creates its own OpenGL extension. But this will evetually (if it succeeds, that is) become a standard extension (i.e. ARB extension) and later become part of the OpenGL standard. Many games don't even use some of these features, because the market share of the hardware supporting them isn't large enough yet. (Though gamers are fast to upgrade their hardware.)
Also, don't forget that you have to write hardware-specific code even with DirectX, because you really don't want DirectX to use the software rendering for you. You'll have to check if a certain feature is hardware supported, and you usually need a slightly different algorithm in case it's not.
I think the main reason for DirectX's success is that most games are Windows only anyway, and that DirectX is more than Direct3D. If you write a Windows game, you'll have to use DirectInput, DirectSound etc. anyway, because it's the only standard API offering input, sound etc. functionality for games on the Windows platform. But if you have to use DirectX anyway, why not use all of it?
Yet another reason might be the object-orientation hype that's going on. Obejct orientation is marketed as an extra feature, not as a design choice. (Whether the design choice is justified I don't know, I'm not a 3D developer, though I've played around with OpenGL a bit.)
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I see this "If you code in DirectX, at least it will work on all cards" canard repeated so often, I can only marvel at Microsoft's propaganda machine and the essential stupidity of mankind. Why do you think so many new DirectX games fail to work under a number of cards until they release patches?
As someone who's coded in both (and Direct X for a game that must support a wide range of cards), an OpenGL program is far more likely to work on a given range of cards if you haven't coded in explicit support for those cards. The equivalent DX program will require far more setup and test code.
People don't seem to understand this about Direct X: It supplies a feature set, but different cards implement different parts of that feature set. You have to *explicitly test* almost any feature you can name to see if the card can support it, via "capability bits". Try getting hold of the DX caps viewer, and you'll be able to see just how many of them there are.
In fact, it's worse than that. Because old drivers often lie about their caps. (Hello Virge.) Also, the caps, especially the texture caps, often don't map nicely to a card's capabilities. So the only real way of seeing whether a particular texture stage setup will fly is to try it, and see if the driver rejects it. Plus there are the weird-arse ones like the NVIDIA 8-stage setup where they jump through the hoops of the DX API to expose their register combiner functionality. (Functionality that is directly exposed in OpenGL, BTW.) Cards also have different capabilities depending on which release of direct X their drivers support. So the same card can report completely different caps depending on driver version. It's a support and programming nightmare.
The only real way to deal with all this is know what each card is capable of, read the manufacturer's release materials, and spend time on the DX mailing list. You spend a lot of time programming a particular effect in a number of different ways, and hope like hell all your combinations cover all the cards out there. You cannot guarantee a particular card will work with your app until you test it.
You may assume that DX provides fallback paths for some features, but you'd be wrong. Or where it does, it does it in a braindead way; because your card lacks fabby next-generation feature X, and you requested it, wham, it emulates the *entire* pipe in software instead of just feature X. You lose T&L, and your framerate slows to a crawl. Then you either code your own pipe to do feature X on the CPU and then hand off properly to the card, or you just go without. Either way involves a lot of testing code. OpenGL is much, much better about falling back gracefully.
I'm also not clear on why people think DirectX has a technical edge. Microsoft do a fine job of going to the current hot hardware vendor, incorporating their upcoming features in their API, and then making a lot of noise about it. But you could access vertex shaders on the GeForce3 from OpenGL on the Mac before you could ever use them from DX. The OpenGL extension mechanism means that when a part comes out, you almost immediately have access to its new features, rather than having to wait for the next DX rollout. (Remember, NVIDIA had to install a "back door" to provide access to the full register combiner functionality of geforce1-2 cards from DX. Many people don't even know it exists.) Go to NVIDIA's web site and ponder how many of their tech demos these days are in OpenGL.
The only thing DirectX has going for it, its so-called unified API, makes no difference at all in the end. You end up doing exactly what you'd do in OpenGL -- testing for certain cards, and using their exposed abilities if they exist. Writing a lot of fallback code. In the end, you're better off going with the card manufacturer's APIs, IMHO.
Think of it this way: rather than exposing a unified API, DX exposes *every possible API*. So many wonderful standards to choose from! If you're a unix guy: DX8 is the X11 of the 3D graphics API world.
A.
P.S. Sheesh, I haven't even touched on the headache that is resource management in DX.
P.P.S As someone who has to deal with all this shit (card compatibility), I'm a mite touchy on the subject =)
I think these "hardcore gamers" have been lying to you. Saying they use Linux makes them look more l33t. It's better for serving, definitely - but in terms of actually playing games, there's no advantage to using Linux and several disadvantages.
There are lots of things that Linux absolutely blows Windows away at. Gaming isn't one of them.
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