OpenGL 3 & DirectX 11: The War Is Over

Features
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published

Shader Model 5

With Shader Model 5, Microsoft applies certain concepts of object-oriented programming to its shader language, HLSL. Unlike preceding versions, which introduced new capabilities (Dynamic Branching, integer support, etc.), the purpose here is to facilitate programmers’ work by solving a common problem in current game engines: namely the upsurge in the number of shaders due to the large number of permutations. We’ll take a concrete example: Suppose that an engine manages two types of materials, plastic and metal, and two types of light: spot and omni. A programmer has to write four shaders in order to handle all cases:

renderPlasticSpot ()…// rendering plastic using spot light …

renderPlasticOmni ()…// rendering plastic using omni light…

renderMetalSpot()…//rendering metal using spot light ...

renderMetalOmni()…//rendering metal using omni light…

This example is very simple since there are only two materials and two types of light, but in practice there can be several dozen. Obviously doing it this way can quickly become unmanageable. There’s a tremendous amount of code duplication and each time a bug is corrected somewhere it has to be corrected in all the other shaders. To solve this problem, programmers use what’s commonly called an über–shader, which brings together all the combinations:

Render()#ifdef METAL// code specific to metal material #elif PLASTIC// code specific to plastic material #endif#ifdef SPOT// code specific to spot light#elif OMNI// code specific to omni light#endif

This solution solves the problem by generating shaders on the fly from common code fragments. The downside is that it makes reading the shaders difficult and requires additional effort to be sure that all the fragments are inserted where they need to be. But with Direct3D 11, it’s now possible to make your code much more legible by using a derived interface and classes:

Light myLight;Material myMaterial;Render()myMaterial.render ();myLight.shade ();

Light and Material are interfaces, and the code is contained in the derived classes OmniLight and SpotLight, PlasticMaterial and MetalMaterial. So the code is all in a single place, which makes bug correction easier. At the same time, legibility doesn’t suffer thanks to the organization of the code, which resembles the concept of virtual functions in object-oriented languages. This feature will be welcomed by programmers, but won’t have any real impact for gamers.

Miscellaneous

As you can imagine, we’ve only skimmed the surface of Direct3D 11’s new features and Microsoft hasn’t even released all the details yet. Among the topics we haven’t mentioned are the increase in maximum texture size from 4K x 4K to 16K x 16K and the possibility of limiting the number of mipmaps loaded in VRAM. There’s also the possibility of changing the depth value of a pixel without disabling functionality like early Z checking, support for double-precision floating-point types, scatter memory writes, etc.

Fedy Abi-Chahla
109 Comments Comment from the forums
  • Gatekeeper_Guy
    Cool, but it will be a few years before we see at DX11 graphic card on the market.
    Reply
  • stridervm
    Sadly, I agree by the author's opinions. Not simply for, but because it still give away the idea that PC gaming cannot be considered serious..... Unless you're using Windows, which is proprietary, the only viable alternative cannot be used because of the fear of losing compability. I just hope this can be remedied before Microsoft becomes.... Unreasonable and becomes power hungry..... If it isn't already. Look at how Windows systems cost now compared to the the alternative.
    Reply
  • johnbilicki
    DirectX 11 will be available on Windows 7 and Vista? Great news indeed! Normal noobs will be able to own super noobs who are standing around looking at over-detailed shrubs.

    As for real gamers, we'll stick with XP until either Microsoft gets smart and clones XP and only adds on Aero or OpenGL gets it's act together and Linux becomes a viable gaming platform. It would be nice if it became a viable anything-other-then-a-web-server viable platform though. Linux gurus, feel free to let us know in sixty years that I won't have to explain to my grandmother how to type console commands to install a copy of Opera.

    OpenGL can go screw backwards compatibility, look what it's done to (competent) web designers who are stuck dealing with Internet Explorer.

    All the bad news about DirectX, OpenGL, and DRM makes me wonder if these companies want us to pirate the hell out of everything. At this rate "next generation" consoles might actually become the next generation consoles!
    Reply
  • jimmysmitty
    Gatekeeper_GuyCool, but it will be a few years before we see at DX11 graphic cardhttp://en.wikipedia.org/wiki/Video_card on the market.
    I thought the article said that DX11 is supposed to be compatable with previous gen hardware.

    I know the Gemoetry Shader with Tesselation is already in all of the ATI Radeon HD GPUs so thats one thing it will support.

    But no SP 5.0 support. I have heard that Intels GPU, Larrabee will support DX11. So that would mean late 2009/2010 will have at least one and that should mean that ATIs HD5K series and nVidias next step should includ support if they were smart and jumped on the wagon early.
    Reply
  • OpenGL may not have gotten the changes it needed to compete with DirectX as a gaming graphics API. But then you have people like Tim Sweeney telling us that graphics APIs are not going to be relevant that much longer (http://arstechnica.com/articles/paedia/gpu-sweeney-interview.ars).

    Direct3D 10 has changed very little in the industry so far, predictably only a very small number of games us it. And those who do can do most of it on Direct3D 9 as well. Maybe MS learned by now that releasing a new API on only the latest platform is a huge mistake, but it will still be a while before people will adapt their new API. And if Tim Sweeney's predictions come true, it will likely not happen at all.
    Reply
  • martel80
    johnbilickiLinux gurus, feel free to let us know in sixty years that I won't have to explain to my grandmother how to type console commands to install a copy of Opera.I have been able to "accidentally" (because I'm no Linux guru, you know) install Opera through the Synaptic Package Manager on Ubuntu. So please, stop talking nonsense. :)
    The process was a bit different but overall faster than under Windows.
    Reply
  • dx 10 may not appear major but for devs its actually is.. no more checking cap bits.. that is a big improvment. dx10 is alot more strict in terms of what the drivers should do and thats good. doing away with fixed functions is also great

    however hardware tesselation if huge.. dx 11 also allows for hardware voxel rendering /raymarching thru compute shaders and alot of other stuff.. as apis become more general im sure the pace of new apis: will slow down, but that's not a indicator that pc gaming is dying (un informed people have claimed that the pc is dead since the ps1)

    as for the windows/other platforms discussion, it is not the fault of microsoft that there is no viable alternative on other platforms. if someone chose to compete with microsoft, they could. but no one seems willing. what really should be done is a port/implementation of dx11 in open source..

    however, in the cut throat buisness of game engines and gpu drivers, i seriously doubt that open source systems will ever be at the forefront of gaming
    Reply
  • phantom93
    DX11 is compatiable with DX10 hardware. It should work when it is released unless they have bugs.
    Reply
  • spaztic7
    From my understanding, all HD4800 serious are DX11 compatible... and the HD4800 line is ray tracing compatible at ray tracings frame cap. I do not know about the 4600 line, but I don’t see why they wouldn’t be.
    Reply
  • GAZZOO
    ow PC gameing is dieing allright the major game componies are starting to squeese out the PC games from there production list useing the excuse that they are loosing money through pirecy but what they are realy doing is cutting out one version forcing PC gamers to evolve into console players
    And from this article I get the impresion that microsoft has a hand in it aswell by making sure that the console games end up running better or as good as PC games
    I think if the origenal Opengl was alowed to proceed years ago and if the follow up was taken and there wasnt any sabotage happening then the PC and its performance with mutly CPU GPU and the tecnolegy evolving with the progamers and propper apis in this area would have left the console market in the shade but this way Microsoft is eliminating other similar competion Apple
    To cut to the chace Apple and OpenGl is getting the Microsft squeese and who has an interest in a console product :-)
    I guess I might be one of the old dinosorse but I still am a PC gamer through and through even though I am grampar foda I love buiding PC units and playing well I havent been to a net game in a couple of years Pizza and beer he he heee But Il be buggered If I will lie down and die because of big buisness
    Gazza
    Reply