OpenGL vs DirectX - a fresh look

[Bucic]

 

A few months ago, the Khronos Group announced the release of OpenGL 4.0, bringing it to "feature parity" with DirectX 11, including the much-advertised tessellation shaders and instanced geometry shaders. More recently, OpenGL 4.1 fixed some lingering complaints(...)

 

http://blog.wolfire.com/2010/01/Why-you-should-use-OpenGL-and-not-DirectX

 

and the follow-on

 

http://blog.wolfire.com/2010/08/OpenGL-update

[GaryIKILLYOU]

I don't seem to understand the major plus of programming in OpenGl, is there really any benifit of choosing it over DirectX other than Linux support?

[Bucic]

I won't add anything to what the author already said :)

[Pilotasso]

I remember when I ran OpenGl back in the day it would run faster on my GPU than DirectX.

[Pyroflash]

The benefit is that OpenGL is open to the developer creating new libraries or modifying existing ones. This makes it far more flexible than DirectX.

[winz]

Even Carmack, once a great advocate of OpenGL is saying that OpenGL just missed the train and has fallen way behind. On the other hand, direct3D has matured and the situation now is totally different from 1997. OpenGL is playing catchup.

The biggest advantage of direct3D is that it has a big company backing it up and handling the communication with big hw players, nvidia and amd.

 

And keep in mind that your arcticle is almost one and half year old...

[Bucic]

Even Carmack, once a great advocate of OpenGL is saying that OpenGL just missed the train and has fallen way behind.

 

I see that not everyone even care to read the article, so here's a chunk

While many games participate in Microsoft's marketing charade, more savvy graphics programmers like John Carmack refuse to be swept up in it. He put it this way, "Personally, I wouldn’t jump at something like DX10 right now. I would let things settle out a little bit and wait until there’s a really strong need for it."

 

And keep in mind that your arcticle is almost one and half year old...

I know. Do you know in which way has the status drifted since then?

[winz]

That Carmack line is totally out of context, it's from a 2007 game informer article, when directX 10 was a totally new api and only the most expensive cards were able to handle it. He followed the line with

"I especially like the work I’m doing on the [Xbox] 360, and it’s probably the best graphics API as far as a sensibly designed thing that I’ve worked with,"

Guess what api he was refering to ;)

 

Using lines so out of context doesn't give much credibility to your arcticle.

 

edit:

I know. Do you know in which way has the status drifted since then?

Something more recent

http://www.tomshardware.com/news/john-Carmack-DirectX-OpenGL-API-Doom,12372.html

Edited May 19, 2011 by winz

[Moa]

@winz: nb: theOpenGL-vs-DirectX comments by Carmack you talk about are as out of date as the comments he made in 1997. Here is why ...

 

They were made when OpenGL was stagnating and not matching DirectX for features. Ever since the Khronos Group have taken stewardship of OpenGL it has leapt ahead - to the point where it matches DirectX. There are also features where OpenGL is ahead (and vice versa), eg. better 'picking'.

 

So, if OpenGL and DirectX have similar-enough parity in terms of features you might want to consider OpenGL for the following reasons:

 

* OpenGL is generally considered easier to program. DirectX since 9 has slowly been converging to a model similar to OpenGL, but OpenGL is still much easier to work with, IMHO (doesn't have as much Windowsesque cruft). The OpenGL fixed functionality pipeline is easier, and for more modern work GLSL is nicer than HLSL. Please note that I do OpenGL programming, so it's not just something I read, it's something I use as a developer (in fact, I hope to show some of my hobby work in these forums next week - and it will be OpenGL based).

 

* OpenGL is cross-platform. Not just Linux, but Windows too! and Macs, and Android, and iPhone, and PS3, and Unix, oh yeah, did I say Windows. OpenGL works on pretty much everything except the XBox (where it could, but Microsoft have deliberately keep it out). Think cross-platform doesn't matter? Well, choosing it made $3.5 millions dollars personally for the creator of X-Plane when it was ported to the iPhone - something he says he couldn't do if he had chosen DirectX. Please see:

http://techhaze.com/2010/03/interview-with-x-plane-creator-austin-meyer/

 

In fact, true cross-platform (not Microsoft's warped definition of 'cross-platform' which means 'maybe works between Windows releases') is going to be be *more important* in the future, not less important. The Windows PC is still important, and important for gaming, but the revenue fraction from it will decrease over time as consoles and phones/pads and consumer devices we haven't yet thought of are all emerging. These pretty much all run a flavour of OpenGL called OpenGL ES (which is essentially the same as standard OpenGL, with some features removed to get it into silicon).

 

If OpenGL didn't work on Windows then the cross-platform argument would be moot, and clearly DirectX would then be better than OpenGL in an imaginary world where OpenGL didn't work on Windows. The fact is OpenGL works on Windows and everything else, while DirectX is limited to Windows (and version-limited with XP) and XBox.

 

* As someone pointed out, OpenGL has an extension mechanism that standardises OpenGL access to particular features of your hardware. The equivalent in DirectX (at least older versions) is device capabilities, which are a pain to use in comparison, and make programming more complex.

 

* There is more than one implementation of OpenGL. This is a good thing as it means if it doesn't suit one particular vendor's interest to keep developing it then other vendors will still provide it (eg. Mesa, Intel, Nvidia, ATI, etc - none of these are likely to evaporate soon). Here's one example, Microsoft don't do DirectX 10 or 11 features on Windows XP - the true reason for this is they want you to pay to upgrade to a newer version of Windows. Meanwhile, if you have the correct graphics card and OpenGL drivers you can get DirectX11-equivalent functionality on Windows XP if you want through OpenGL and OpenGL extensions. Not only does this mean gamers would not be forced to upgrade (they could move off Windows XP when it was convenient for *them*, not when it was convenient for Microsoft). For companies this forced upgrade can be significant sums of money for licensing, and even more for training.

 

The downside of OpenGL is two-fold:

 

* for a while OpenGL implementations got less attention than DirectX. This is changing of late, mostly due to the use of OpenGL ES in the rapidly-expanding gadget market. So, I think this situation is very likely to change.

 

* some tools are DirectX only. This is mostly a legacy of the Windows dominance of computing (now rapidly fading). However, apart from game-oriented tools most professional graphics tools have DirectX and OpenGL implementations. This is because professional rendering shops (eg. like Weta Digital currently making the two Hobbit movies in my city) use huge clusters of Linux boxes (they're cheap!) to do the rendering, so OpenGL and OpenGL based tools are needed by the pros.

 

DirectX has its place (mostly Windows-only gaming). Elsewhere it is an OpenGL world (which is not visible to most consumers).

Edited May 19, 2011 by Moa

[Bucic]

It seems that you're trying to imply that the author claims that Carmack is all OpenGL uber alles.

 

From the OP article:

As John Carmack said when asked if Rage was a DirectX game, "It’s still OpenGL, although we obviously use a D3D-ish API [on the Xbox 360], and CG on the PS3. It’s interesting how little of the technology cares what API you’re using and what generation of the technology you’re on. You’ve got a small handful of files that care about what API they’re on, and millions of lines of code that are agnostic to the platform that they’re on."

 

As you can see the article does not hide the fact that Carmack uses Xbox 360 API too. So I kindly ask you to read both articles through and through before trying to disprove an argument the author never made, again. And it's not my article.

 

 

As for the article in general - I thought it's interesting so I posted it here too. I know too little about OpenGL to make my own detailed statements. The article is rather short and simply written so for heaven's sake people, read it before posting. If you don't agree with the article and you're not Moa (edit: speaking of the devil :)) feel free to comment on it so that author has a chance to answer your points.

 

Edit:

Moa, thanks for your input. Always appreciated!

 

Oh, and a... :P

http://techhaze.com/2010/03/interview-with-x-plane-creator-austin-meyer/

I bet on OpenGL, and used that. As a result, here we are, 15 years later, and the people that use Direct3D can support Windows only. But, with OpenGL, I support Windows, Mac, Linux, Palm OS, Google Android OS, and oh yes: iPhone and iPodOS which are also OpenGL. So having X-Plane in OpenGL let me move over to iPod and iPhone very quickly. The port was done in 2 weeks, to be very exact. And you saw that i have moved 500,000 units on the iPhone and iPod since. I get $7 from each of those sales, and have moved 500,000 units in the last year and a half, so get out your calculator, do some math, and see if i made the right choice to bet against Microsoft 15 years ago.

Edited May 19, 2011 by Bucic

[topdog]

IMO the best reason for both is to spur competition. DirectX may not be where it is today had Carmack not shown what the competition was capable of. Then DX set the pace and it's GL that picked up its heels to keep up and keep itself noticed.

 

The more they do this, the better for us, and that's the bottomline for consumers :)