OpenGL 3 & DirectX 11: The War Is Over

The Revelation

No more was heard of OpenGL 3 until August 2008 at the SIGGRAPH conference. But while some people were expecting a pleasant surprise, Khronos had a serious disillusionment in store for fans of OpenGL. Not only was the API nearly a year late, but to top it all off, most of the new aspects of Longs Peak had been completely abandoned. After the OpenGL 2.0 fiasco, which really delivered only an OpenGL 1.6 with a different name, this OpenGL 3.0 was beginning to look like no more than version 2.2. The unpleasant surprise, coupled with the absence of communication for several months, resulted in some very aggressive reactions toward the Khronos group on forums everywhere. Faced with the storm of reaction, Khronos responded on the official OpenGL forum through Barthold Lichtenbelt of Nvidia. His highly detailed response at least provided a little insight into what had been going on in the wings. We learned, for example, that certain points of implementation weren’t decided on in time, and that in parallel, a lot of people felt that it had become urgent to enable OpenGL support for the latest GPUs. So the plan was modified in order to extend OpenGL 2 to include Direct3D 10 functionality.

Even if the argument holds up, Khronos can still be criticized for not trying to put out the fire immediately rather than suddenly cutting off all communication with the outside world. And the similarity with what happened six years earlier with OpenGL 2.0 doesn’t really inspire optimism for the future. After two promises to rewrite the API—both of them failures—how are we supposed to have faith in the future of OpenGL? Finally, a comment by John Carmack at the latest QuakeCon didn’t really help the situation. Asked about the status of OpenGL 3, he answered in terms that were a lot less politically correct than Mr. Lichtenbelt’s statement.

According to Carmack, OpenGL 3’s falling short of what it was supposed to be is mainly the fault of certain CAD software developers who weren’t really favorable to Longs Peak. They were afraid of problems with compatibility and their applications due to the disappearance of certain older functions. That version was tacitly confirmed by Lichtenbelt: “ During the Longs Peak design phase, we ran into disagreement over what features to remove from the API...The disagreements happened because of different market needs...We discovered we couldn’t do one API to serve all..”

So in the end, OpenGL 3 is nothing more than an incremental update. The API hasn’t really been changed. Khronos has simply marked certain capabilities as being deprecated and created a context in which using those functions will cause errors. That’s a far cry from what was promised (driver developers still need to provide support), but it is a step forward since it allows developers to prepare for future versions that may finally offer a true Lean and Mean mode. OpenGL 3 also introduces the notion of profiles. For the moment there’s only one profile, but the plan calls for creating a profile for games and another for CAD, for example, with each profile supporting a different subset of functions.

Aside from that, the features offered by OpenGL 3 are pretty much the same as what Direct3D 10 offers, except for Geometry Shaders and Geometry Instancing, which have been added to the API as an extension. But some features of Direct3D 10.1, like independent blending modes for MRTs, are also supported.

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  • mi1ez
    So, is the tesselation stage similar to AF or bi/trilinear filtering?
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  • JDocs
    Tesselation, from what I've seen, takes a simple model intended for say a 4650 and "upgrades" it in memory making it more complicated and details for higher end cards. If I understand this correctly it will drastically reduce development time and costs while increasing visual quality.
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  • Anonymous
    Hmm, not sure about "upgrading" in memory. I looks like it just lets you pass in the control points that define your geometry rather than passing in all vertices for the mesh, which you yourself would probably have defined in a similar manner anyway.
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  • Anonymous
    Direct3D remains utterly irrelevant to me as a Linux user.
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  • bobwya
    shrugDirect3D remains utterly irrelevant to me as a Linux user.


    But it is relevant to a lot of GNU/Linux users as the Wine programmers have to compatiblise what M$ implements in their 3D API... Currently they are making a dogs dinner of DirectX 9.0 support. However Windows games are generally well supported if they have an OpenGL option... Far Cry for example will not render under Wine in DirectX mode but when switched to OpenGL it works very well.

    It is sad to hear about the difficulties OpenGL is having therefore.

    Bob
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  • Scooby2
    Tessellation as far as I'm aware is adding more triangles to a model to give smoother surfaces over curves. It does not add any visual details but does add to the complexity of the model.
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  • Scooby2
    Quote:
    adding more triangles


    It breaks down the existing geometry into smaller triangles. (most 3d models are built out of triangles to begin with)
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  • mayones
    Very good aricle, thanks! I'm an OpenGL developer as well, and I wish it the best. I think that now, OpenGL needs money and commercial support - unfortunately these are the rights of current world. It would be a shame to have only one modern 3D API...
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  • marmot
    "the professional market, where OpenGL is the standard"
    what market are you talking about? Please detail. Your readers are mostly common computer users, not specialsts knowing in-depth details about the computer graphics market.

    "Since the ARB—the group in charge of ratifying the API’s development—included many different, competing companies.."
    What are the most important members of this ARB? Whose words have big weight in that group? The readers might be curious - who are the people generating the conflicts that slow down the OpenGL evolution?

    And by the way, why ATI and nVidia don't just take care about OpenGL and ignore that silly ARB? If they can't because of patents and such, they should make a new API from the scratch. Im pretty sure they are more than capable of it.
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  • sckoobs
    The problem with OpenGL is that industry users (e.g. CAD and scientific users) are opposed to change in the API which is blatantly against the ethos of the games development community. Industry users have already spent a lot of money on the OpenGL apps, so naturally they don't want the features they use to die. I think that what Khronos has done to date is the most logical route to take given the constraints they are working within.

    The ideal solution would be to cut any ties that lead to a conflict of interest and pursue untainted API refreshes as they had originally promised.

    As a cross-platform developer I want OpenGL to be a true competitor to D3D, I don't use anywhere near the full feature set of what current versions provide but if it looses at the top end, support will dwindle and the bottom end will also be affected.
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  • khelben1979
    If OpenGL even have a chance of competing against DirectX 10, then I'm more than impressed! OpenGL is the way to go for Linux and I and many others with me would like to use Linux as an gaming platform instead of Windows.

    I'm very tired of using Windows and I don't like the operating system. It works, but it isn't very fun, unlike Linux which IS a enjoyable experience and feels fast even on old computer hardware, unlike Windows which never get the power it needs.
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