From Evolution to Expansion and Multi-Threading: The Mile High Overview

The November DirectX SDK update was the first to include some DirectX 11 features for developers to try out. Of course, there is no DX11 hardware yet, but what is included will run on the current DX10 setup with DX10 hardware under Vista and the beta Windows 7. This combined with the fact that Khronos finished the OpenCL specification last month mark two major developments on the path to more general purpose computing on the GPU. Of course, DX11 is more geared toward realtime 3D and OpenCL is targeted at real general purpose data parallel programming (across multiple CPUs and GPUs) distinct from graphics, but these two programming APIs are major milestones in the future history of computing.

There is more than just the compute shader included in DX11, and since our first real briefing about it at this year's NVISION, we've had the chance to do a little more research, reading slides and listening to presentations from SIGGRAPH and GameFest 2008 (from which we've included slides to help illustrate this article). The most interesting things to us are more subtle than just the inclusion of a tessellator or the addition of the Compute Shader, and the introduction of DX11 will also bring benefits to owners of current DX10 and DX10.1 hardware, provided AMD and NVIDIA keep up with appropriate driver support anyway.

Many of the new aspects of DirectX 11 seem to indicate to us that the landscape is ripe for a fairly quick adoption, especially if Microsoft brings Windows 7 out sooner rather than later. There have been adjustments to the HLSL (high-level shader language) that should make it much more attractive to developers, the fact that DX10 is a subset of DX11 has some good transitional implications, and changes that make parallel programming much easier should all go a long way to helping developers pick up the API quickly. DirectX 11 will be available for Vista, so there won't be as many complications from a lack of users upgrading, and Windows 7 may also inspire Windows XP gamers to upgrade, meaning a larger install base for developers to target as well.

The bottom line is that while DirectX 10 promised features that could bring a revolution in visual fidelity and rendering techniques, DirectX 11 may actually deliver the goods while helping developers make the API transition faster than we've seen in the past. We might not see techniques that take advantage of the exclusive DirectX 11 features right off the bat, but adoption of the new version of the API itself will go a long way to inspiring amazing advances in realtime 3D graphics.

From DirectX 6 through DirectX 9, Microsoft steadily evolved their graphics programming API from a fixed function vehicle for setting state and moving data structures around to a rich, programmable environment enabling deep control of graphics hardware. The step from DX9 to DX10 was the final break in the old ways, opening up and expanding on the programmability in DX9 to add more depth and flexibility enabled by newer hardware. Microsoft also forced a shift in the driver model with the DX10 transition to leave the rest of the legacy behind and try and help increase stability and flexibility when using DX10 hardware. But DirectX 11 is different.

Rather than throwing out old constructs in order to move towards more programmability, Microsoft has built DirectX 11 as a strict superset of DirectX 10/10.1, which enables some curious possibilities. Essentially, DX10 code will be DX11 code that chooses not to implement some of the advanced features. On the flipside, DX11 will be able to run on down level hardware. Of course, all of the features of DX11 will not be available, but it does mean that developers can stick with DX11 and target both DX10 and DX11 hardware without the need for two completely separate implementations: they're both the same but one targets a subset of functionality. Different code paths will be necessary if something DX11 only (like the tessellator or compute shader) is used, but this will still definitely be a benefit in transitioning to DX11 from DX10.

Running on lower spec'd hardware will be important, and this could make the transition from DX10 to DX11 one of the fastest we have ever seen. In fact, with lethargic movement away from DX9 (both by developers and consumers), the rush to bring out Windows 7, and slow adoption of Vista, we could end up looking back at DX10 as merely a transitional API rather than the revolutionary paradigm shift it could have been. Of course, Microsoft continues to push that the fastest route to DX11 is to start developing DX10.1 code today. With DX11 as a superset of DX10, this is certainly true, but developer time will very likely be better spent putting the bulk of their effort into a high quality DX9 path with minimal DX10 bells and whistles while saving the truly fundamental shifts in technique made possible by DX10 for games targeted at the DX11 hardware and timeframe.

We are especially hopeful about a faster shift to DX11 because of the added advantages it will bring even to DX10 hardware. The major benefit I'm talking about here is multi-threading. Yes, eventually everything will need to be drawn, rasterized, and displayed (linearly and synchronously), but DX11 adds multi-threading support that allows applications to simultaneously create resources or manage state and issue draw commands, all from an arbitrary number of threads. 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.

With 8 and 16 logical processor systems coming soon to a system near you, we need developers to push beyond the very coarse grained and heavy threads they are currently using that run well on two core systems. The cost/benefit of developing a game that is significantly assisted by the availability of more than two cores is very poor at this point. It is too difficult to extract enough parallelism to matter on quad core and beyond in most video games. But enabling simple parallel creation of resources and display lists by multiple threads could really open up opportunities for parallelizing game code that would otherwise have remained single threaded. Rather than one thread to handle all the DX state change and draw calls (or very well behaved and heavily synchronized threads sharing the responsibility), developers can more naturally create threads to manage types or groups of objects or parts of a world, opening up the path to the future where every object or entity can be managed by it's own thread (which would be necessary to extract performance when we eventually expand into hundreds of logical cores).

The fact that Microsoft has planned multi-threading support for DX11 games running on DX10 hardware is a major bonus. The only caveat here is that AMD and NVIDIA will need to do a little driver work for their existing DX10 hardware to make this work to its fullest extent (it will "work" but not as well even without a driver change). Of course, we expect that NVIDIA and especially AMD (as they are also a multi-core CPU company) will be very interested in making this happen. And, again, this provides major incentives for game developers to target DX11 even before DX11 hardware is widely available or deployed.

All this is stacking up to make DX11 look like the go-to technology. The additions to and expansions of DX10, the timing, and the ability to run on down level hardware could create a perfect storm for a relatively quick uptake. By relatively quick, we are still looking at years for pervasive use of DX11, but we expect that the attractiveness of the new features and benefit to the existing install base will provide a bigger motivation for game developers to transition than we've seen before.

If only Microsoft would (and could) back-port DX11 to Windows XP, there would be no reason for game developers to maintain legacy code paths. I know, I know, that'll never (and can't by design) happen. While we wholeheartedly applaud the idea of imposing strict minimum requirements on hardware for a new operating system, unnecessarily cutting off an older OS at the knees is not the way to garner support. If Windows 7 ends up being a more expensive Vista in a shiny package, we may still have some pull towards DX9, especially for very mainstream or casual games that tend to lag a bit anyway (and as some readers have pointed out because consoles will still be DX9 for the next few years). It's in these incredibly simple but popular games and console games that the true value of amazing realtime 3D graphics could be brought to the general computing populous, but craptacular low end hardware and limiting API accessibility on popular operating systems further contribute to the retardation of graphics in the mainstream.

But that's the overview. Let's take some time to drill down a bit further into some of the technology.

Introducing DirectX 11: The Pipeline and Features Drilling Down: DX11 And The Multi-Threaded Game Engine


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  • Mr Roboto - Thursday, February 26, 2009 - link

    How about this for the Windows 7 release, a DirectX 9 Halo 2 Port For Windows 7 But Needs it DirectX 11 To Run!

    OK so there was and still is no reason that Windows XP couldn't have DirectX 10 or DirectX 11 right? These were just more strong armed tactics by Microsoft to force us to hand them our cash for an aborted OS. Like the 4 year old DirectX 9 Halo port that somehow needed DirectX 10 to run, LOL it still makes me laugh. Whoever though up that idea should be shot. Fucking idiots.

    So how many DX10 games have been released to this day? Ten? How many have been exclusively DX10 like MS wanted? The answer is one the four year old Halo.

    I hope MS continues to hemorrhage money and eventually goes out of business. Nothing would make me happier and it would spur innovation simply by them dying off.
  • MadBoris - Tuesday, February 10, 2009 - link

    Unfortunately the API will not be supported until consoles support it.
    Consoles now control game development technical design, thx to Microsofts sly ways.

    Until next gen consoles come out with the next DX API support then DX9 will still be the standard due to multiplatforming. We can barely get a developer to make the proper PC support changes in their multiplatform games, they aren't going to write seperate render paths unless MS pays them to, like with DX10.

    The only redeeming effect is the Nvidia 8800 GPU is one of the best GPU's I bought because it looks like it will last me many years.
  • vistaisfine - Friday, February 20, 2009 - link

    personally i hope windows LIVE grows. they need it to. its a slick system that works well. at least in dawn of war 2 and gta IV. i don't think your assesment of how quickly developers are adopting DX 10 is accurate. Alot of gaming companys go for a wide demographic and that usually means creating content that can scale depending on the hardware. the reason why there are so many dx 9 game is because the lowest common demoninator gamer runs a dx 9 card. People are finshing maxing out their AGP builds. (crazy as that sounds). Reply
  • Mr Roboto - Thursday, February 26, 2009 - link

    Are you high? GFWL is an abomination. It has absolutely ruined GTA IV as well as all other games associated with it. It's a straight XBox port and it's total shit. There's no dedicated servers, no anti cheat mechanism, no easy way for matchmaking, constant disconnections, I could go on and on. It's very unfriendly and in typical fashion they treat something as trivial as save games as their own property. Go ahead try backing up your GTA IV save games folder and using them on another PC or game installation. It won't work because Microsoft either didn't think about it or more likely purposefully made it difficult because they think it belongs to them and they're in control of it.

    The only value GFWL has for MS (which I should have seen coming) is they're going to launch a digital distribution service. Punks. GFWL is so goddamn broken and yet they're going to try to sell games through it before it's even in decent form? Nice. You can bet they'll be ultra slow to in responding to critical bugs and spyware ready made to steal your info on launch day.

    Fucking garbage. You're settling for garbage. Valve knows how to do things, development, marketing, listening to their fan base, updating their games above and beyond what any other company would do. Even Steam isn't perfect and I'm not asking MS to become them (an impossibility) but Microsoft has a LONG way to come before they're even in the same conversation.

    I hope it crashes and burns even more than it already has because it's ported console junk.
  • jharper12 - Thursday, February 5, 2009 - link

    americunts... that's clever. You got us!! We're idiots! I can't believe we never realized it before! You sir, are pure genius.

    I just feel absolutely terrible that 43 other countries joined us in our latest war. I feel even worse that the entire world economy was brought down by our financial sector that represents about 1% of our $14.33 trillion GDP... I mean I truly feel awful that we are dragging everyone down with us. I wish I could do something about it, but it seems as though everyone believes "americunts are idiots" and then continues to follow us into oblivion. Sorry about that, I wish there was something I could do to help.

  • Matrix888 - Wednesday, February 4, 2009 - link

    I'll not be bother with the 2000 or so comments here and reply every one of them, but this is my 2 cents about VISTA:

    1) Drivers issues - there was some initial problem with drivers issues especially old hardware and lazy 3rd parties. But this wasn't MS fault. I've installed VISTA since day 1 and the only problem encountered was an X-FI driver from Creative...which isn't available until like 9 to 12 months later (and it's a beta!!!). Tell me which new O/S doesn't have drivers problem? Win98 was forever plagued with drivers problem, WIN XP suffers similar fate initially, but once the driver matures, it was ok. Hell i've waited for 1 year for an X-FI driver for Ubuntu 7....finally released and the next thing i did is upgrade to Ubuntu 8 (by the time the driver was releasead, UBuntu 8.1 is made available) and it bombs my X-FI.

    2) Memory hogging - another urban legend by people who have no ideas. VISTA does not works the same way like XP. What's the point of having idle memory and not used? VISTA pre-cache ur memory to make it better. 2GB of RAM ran just fine.

    3) You need a high spec PC for VISTA - BS. I've ran an Atom 330 PC with VISTA Premium with Aero on just fine. Even stress test it by opening tons of apps (including a Virtual PC running XP) and it multitask great with all your everyday apps...MS office, Firefox, e-mails, bit torrent etc....only 2GB RAM.

    4) Gaming performance suffers - if you have a moderately new hardware, you are not going to see any difference. I ran my games max settings at 1680x1050. Runs great.

    5) UAC? - Cmon. It's only because XP users never use any other OS like Linux or MAC/OS and they can't get this idea in their head it's for their own good. Linux and MAC/OS will prompts u administrator and password when u try to install something or do something funny. It is perfectly fine and u can always turn it off.

    So far, i really have minimal problem with VISTA. VISTA MCE makes a great front-end for HTPC and believe this, the start up is MUCH FASTER than XP. Sure a fresh XP will beat VISTA in terms of boot up time, but once you installed tons of apps into it, XP will slow like a turtle while VISTA will have minimal degradtion and you get response to your desktop much faster.

    I've finally migrated all my PCs and notebooks last year to VISTA and dump XP forever.

    I've no doubt Windows 7 will be great, but to me, it'll be nothing more than VISTA Edition 2. It'll be re-packaging to wow idiots who simply believe all those VISTA rumours without ever using it (or try to run it on a Pentium 3). Seriously, nobody ask you to install a 3.0 engine into a Japanese kei-car!!! :x

    For the rest of us, it'll simply be a moderate update of a already fantastic OS.

    Hasta La Vista!
  • volgagerman - Monday, February 2, 2009 - link

    One thing that hasn't been stated yet is that the success of any API is directly related to market forces and timing.

    DirectX 9.0c has been successfull largely for two reasons. One, it took advantage of the market shift that developers would target consoles first and port to PC second in order to extract the largest possible return on investment. Two, many of the gaming engines we enjoy today began their life with the release of DirectX 8. It took 3-4 years for those engines to be built, and they finally meshed with the feature set of DirectX 9, as it was an evolution over 8 and not a true revolution.

    DirectX 10 has not revealed any jaw dropping improvements in shipping titles over 9 because developers are still leveraging those engines for exploitation on the console market. They can easily up the visuals for a port to the PC by removing texture compression, upping resolution support and increasing texture sizes, but the major underlying changes to truly support 10 will not happen in the immediate term.

    That brings me to my next thought. From everything I've read, the next generation of consoles are targeted for release in the 2011-2012 timeframe. A true next-gen game engine takes at least 4 years to fully bake. That means Unreal Engine 4.0, Id Tech 6, next-gen Gamebryo are all now in development to be ready when those next-gen consoles hit. It's a safe bet they are leveraging DirectX 11 to its fullest. To go one step further, I would guess that market forces are not going to change in the future, and game developers will still target consoles first and PCs second. What that means in the 2011-2012 timeframe is a solid install base of DirectX 11 on even low-end PCs by that point. It would be a no-brainer to anticipate Microsoft leveraging it's latest and greatest API in the next generation XBOX. With market forces and timing in alignment, the next-gen gaming engines and the the next-gen consoles are set to take full advantage of DirectX 11. I will expect nothing less than revolutionary changes to the quality of gaming graphics in that time frame.

    Here's one final tidbit. If Microsoft takes Intel's bait and utilizes a 32nm modified version of the Larrabee project for a single chip CPU/GPU solution in the next XBOX, developers will have to shift gears yet again and prepare for a rendering model that is mostly software based. That is beyond DirectX 11 and will lead to even more revolutionary changes...Microsoft would no longer be constrained by the capability of their CPU/GPU, but by the efficiency of the software algorithms to achieve playable frame rates. I look forward to a future on consoles and PCs when a simple patch improves frame rates significantly. No hardware update required. :)
  • mechBgon - Monday, February 2, 2009 - link

    Touching on the "rejected" Vista:

    Valve's monthly user survey was updated today. WinXP lost 2.48% in just the last month, and Vista has gained 2.47% of that. The ratio of Vista to WinXP is now 1 to 1.91. I guess you could say Vista is "picking up Steam," ;) and rapidly, too.

    Ten months ago, this AnandTech thread also indicated (much to the OP's annoyance, I'm sure) that even then, the Vista adoption rate among AnandTech Forum users was already about 50%:">

    In light of the readership's tastes, also pretty clearly illustrated in the comments here, I suggest calming the anti-Vista rhetoric and not reading more into things than what's really there.
  • Hrel - Sunday, February 1, 2009 - link

    Do you think someone over there at anand could do an article explaining exactly WHY DirectX 10 can't be supported by XP? PLEASE!!!!!! Reply
  • DerekWilson - Friday, February 6, 2009 - link

    because Microsoft chose to tie in driver specific features to DX10 that make a retrofit not technically possible. Microsoft could have chosen to spec out DX10 so that new hardware features were exposed while simply allowing for a new driver model, but they did not: they required the new driver model features.

    this stuff has to do with power management, threading, OS managed/virtual memory, hardware virtualization (sharing between software and even VMs), etc...

    Now that what DX10 is eternally locked into existence as is, porting back is not possible. We're in a similar boat with DX11.

    There is ZERO technical reason that microsoft couldn't have chosen at the outset to enable the Geometry Shader, to extend const/register limits, and to do all the other things that game developers actually use on Windows XP. It would have required hardware companies to implement a distinct WinXP DX10 driver and Vista DX10 driver, but now that can't be done.

    The /why/ of no DX10 on XP is that MS simply decided not to make that an option when developing DX10 and built in features extraneous to game development that require the Vista platform.

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