No matter whether we've got a low end or high end system, we all expect the realtime 3D revolution to continue until we achieve near parity with reality. The push forward is backed by many factors including pure hardware performance and brilliant advances in techniques for better approximating what we see. But there's another side to the equation beyond just hardware and developers: there is the graphics API.

Unlike CPUs, graphics hardware (GPUs) do not have a common instruction set upon which tools and software can be built. In order to get the power of the hardware out to the public, we need a common interface that works no matter what GPU is underneath. It's left to the graphics hardware designer to take the code generated by this application programming interface (API) and translate it into something that their chip can use. Because it's the developer's single point of contact, the graphics API is incredibly important. It defines how much flexibility programmers have in using hardware and shapes the world of high performance realtime 3D graphics.

Some of the key work done through the graphics API is taking descriptions of 3D objects in a 3D world, sending those objects and other resources to the hardware, and then telling the hardware what to do with them. There is sort of a step by step process that needs to be followed that we generally call a pipeline. Graphics API pipelines have stages where different work is done. Here's the general structure of a 3D graphics pipeline:

First vertex data (information about the position of the corners of shapes) is taken in and processed. Then those shapes can then be further manipulated and re-processed if needed. After this, 3D objects are broken down from 3D shapes by projecting them into 2D fragments called pixels (this step is called rasterization), and then these pixels are each processed by looking up texture information and using lighting techniques and so on. When pixels are finished processing, they are output and displayed on the screen. And that's the mile high overview of how 3D graphics work.

For the past dozen years (it seems longer doesn't it?), we've seen makers of 3D graphics hardware accelerate two very prominent APIs: OpenGL and DirectX.

We recently touched on advancements tangential to OpenGL in our OpenCL article, but today our focus will be on DirectX. Microsoft's DirectX graphics API is much more heavily used in game engines than OpenGL, in a large part because DirectX tends to move much more quickly and sets the bar for both the hardware and DirectX in terms of feature set and flexibility. That always makes upcoming versions of DirectX exciting to talk about: they define the future capabilities of hardware and expose improved tools to developers. Upcoming DirectX versions are glimpses into our graphical future. Currently we have a lot of DirectX 9 and DirectX 10 games available and in development, but DirectX 11 looms on the horizon.

As usual, Microsoft will be trying to time the release of their next DirectX revision with the release of compatible graphics hardware. As with last time, DirectX 11 will also be released with Windows 7. With the Windows 7 Beta already under way, we expect the OS to be done some time this year.

Microsoft has been rather aggressive with Windows 7 scheduling in light of the rejection of Vista, so it appears they are stepping up to the plate to get everything out sooner rather than later. There was a little more than 4 years between the release of DirectX 9 and DirectX 10. As it hit the streets with Vista in January of 2007, DirectX 10 has just turned 2 and we are already anticipating it's replacement in the very near future. As we will learn, this speedy transition should be very good for DirectX 11 adoption as DirectX 10 hasn't even become pervasive yet: many games are still DirectX 9 only.

But let's take a closer look at what we are talking about before we go any further.

Introducing DirectX 11: The Pipeline and Features
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  • Hrel - Sunday, February 1, 2009 - link

    This is one of the most poorly written articles I've ever read on anandtech. It's like the author couldn't organize his thoughts properly. Also, the speculation was riddled with subjective assumptions. I'm not sure if the author just doesn't know this topic very well or if he hadn't slept in 3 days, but this could have been done much better. Great topic though, and interesting subject matter.
  • GourdFreeMan - Sunday, February 1, 2009 - link

    Derek, the DX10 geometry shader was never really intended to do tessellation, and really should not be thought of as a generalized tessellator. It was designed to offer a generalized hardware implementation of vertex effects such as skinning, vertex blending and tweening (see the dolphin demo in the DX SDX for what I am refering to here).

    If it becomes desirable at some point in time in the future to offer fully programable tessellation, then vertex shader, hull shader, tessellator, domain shader and geometry shader could all be merged into another compute shader earlier in the pipeline to do generalized vertex manipulation.

    Of course, it is also possible that the existing tessellator will prove more efficient as fixed function hardware, and only minor functionality improvements will be added.
  • eXistenZ - Sunday, February 1, 2009 - link


    I just wanted to add, that ATi graphic cards have tesslator included since Radeon 8500, but i can be wrong...
    I remember "Truform" technology, which is working in Serious Sam, or Return to Castle Wolfenstein, and Counter Strike 1.6 (it is not working now in Counter Strike).

    I want to know, if author of this article forgot about it, or im wrong about this technology.

    Sorry for my english, im from Slovakia :)
  • haukionkannel - Sunday, February 1, 2009 - link

    There has been a tessalation unit in ATI cards for some time. It's not the same as is reguired in DX11, but guite near. I think that it was mentioned in the article...

    From what I know is that DX10 has been slow because in most games it's just dx9 with some clued features from dx10 above it. With pure dx10 codepath it would have been faster, but that would have left all those XP-customers out, and would not have been sound economically...
    The author hopes that Win7 win encourage the transfer from XP, so there will be larger amount of DX10 and DX11 platforms. So it would become enonomically possible to make DX11 based games (just leaving out some pure DX11 features so that older dx10 cards could handle the games.) So actually when dx11 games comes out, they would be actually first to make use of all dx10 features...
    Well there are so many dx9 machines in the world that even that will take time. So we will see poor dx10, dx11 performance until the XP customers are not needed by game companies, and even then there are those pure console transfers without any optimization like GTA...
    I hope that "Chattered horisont" from Futuremark shows what DX10 can really do. It is goint to be pure DX10 game, so it can use advantages that dx10 can offer. On the other hand it can be next Crysis that looks really good, but makes your hardware moan for more power. We will see...
  • yyrkoon - Sunday, February 1, 2009 - link

    "On the flipside, DX11 will be able to run on down level hardware."

    Um . . . Eh ? English ?

    "This may not significantly speed up the graphics subsystem (especially if we are already very GPU limited), but this does increase the ability to more easily explicitly massively thread a game and take advantage of the increasing number of CPU cores on the desktop. "

    ... and significantly slow things down even further.

    " These code resources are huge and can be hard to manage without OOP (Object Oriented Programming) constructs. But there are some differences to how things work in other OOP languages. "

    I think you would find many experienced programmers who would say that OOP is a way of programming, not necessarily a language type, and I would have to agree with them. Now if you mean languages that *support* OOP, then sure, I can live with that.

    Also, one other minor thing that kind of bothers me. You speak of Directx 6, but was Directx 6 an actual redistributable ? I definitely do not remember it, but I *do* remember Directx 5, Direct 7, 8, . . . and even that thing MS claims never existed . . . WinG.
  • DerekWilson - Friday, February 6, 2009 - link

    down level hardware == hardware that meets a lower DX spec (like DX10 hardware).

    allowing games to be more mulithreaded using a fine grained synchronization scheme ala DX11 should not slow things down if developers take advantage of it correctly (which will be much easier than doing your own management here).

    yes i did mean languages that support the OOP model.

    DX6 was a Win98 thing ... it existed and actually was (iirc) the first version of DX to be hardware accelerated ... at least that's how I remember it.

    DX4, on the other hand, never existed -- MS skipped from DX3 to DX5.
  • frozentundra123456 - Sunday, February 1, 2009 - link

    I was initially unhappy with both Vista and DX10. However, I have come to accept Vista, but dont know if it is that much improved over WinXP. I only have Vista because I bought a new computer with that OS intstalled. I dont really know of anything I do with Vista that could not be done with XP. The only advantage to Vista is that it is supposedly more secure than XP, but I never had any major security problems with XP, nor have I had any with Vista.
    DX10 is still more of a disappointment to me. It requires too many resources and does not seem to offer corresponding improvements in visual quality. Nearly every game I have that is DX10 compliant, I run in DX9 mode because the performance improvement in DX9 more than makes up for the slight visual improvement with DX10. (Yes, I know I need a better graphics card.) I have an HD2600 pro, which was supposedly a "mid range" DX10 card when it came out, and it is virtually worthless for trying to play in DX10 mode, as I stated above.
    I wonder if DX9 will still be supported when DX11 comes out. If not, they had better make DX11 run better on low to midrange hardware than DX10, or there will be a lot of unhappy users.
  • epyon96 - Saturday, January 31, 2009 - link

    Since Derek claims that Direct X 11 is simply a superset of Dx10, why does Microsoft release it simply as 10.2 instead? I am curious what makes a Direct X version and what determines an incremental move forward.
  • ltcommanderdata - Saturday, January 31, 2009 - link

    I'd like to know that too. Since to me DX9.0c (SM3.0) seems to have been a pretty major step forward from DX9.0 (SM2.0), even a whole new shader model, yet it was only given a letter subscript. It should have at least been DX9.1.

    My cynical view? It's all marketing and Microsoft appeasing hardware vendors for their own benefit. For example DX8.1 was supposed to be a decent step forward, going from SM1.1 to SM1.4 with longer shaders and other features. Yet nVidia refused to support SM1.4 and managed to convince Microsoft to call SM1.3 DX8.1 compliant even though it's closer to SM1.1 than SM1.4. My suspicion is that Microsoft agreed with nVidia, because at that time nVidia was making the GPU for the XBox and Microsoft needed them.

    A similar situation occurred with DX9.0c and SM3.0. This time ATI wasn't going to offer immediate support for SM3.0 in their GPUs. So in order for ATI's X8xx generation to not look so far behind, SM3.0 was only marketed as DX9.0c instead of DX9.1 or something more major. Why would Microsoft appease ATI? Conveniently, ATI was making the GPU for Microsoft's next-gen XBox 360, so Microsoft needed them.

    This might not actually be true, but it's interesting that the swings in XBox GPU choice corresponds with Microsoft's degree of emphasis on DirectX capability.

    In the case of DX11, I think there is sufficient new capabilities with Tessellation and Compute Shaders to justify a major number increase. I believe what Derek means is that DX11 is a superset of DX10 in the same way DX9 is a superset of DX8. They both offer backwards compatibility. In contrast, DX10 is not compatible with DX9 and Vista actually has separate DX10 and DX9 APIs (and third Vista specific DX9.0L) while DX8, DX7, etc can run on the DX9 API.
  • GourdFreeMan - Sunday, February 1, 2009 - link

    Microsoft originally had some soft guidelines in this respect. Letter releases were to represent minor changes in the API such as the range and precision allowed for constants, max number of loop iterations in pixel and vertex shaders, etc. Point releases would permit added functionality to stages of the rendering pipeline. Version releases could include changes to the rendering pipeline itself. In practice, point and letter releases have been to support vendor-specific functionality, and version releases have set a baseline for all vendors.

    Microsoft's guildelines fit for all DirectX changes except 9.0c, which was really a vendor-specific change to fit the nVIDIA 6000 series hardware. (ATi did not have SM3.0 cards until its next hardware generation).

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