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.
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ssj4Gogeta - Saturday, January 31, 2009 - link
"DX11 offers nothing new over DX10, as quoted in the article its just a strict superset that builds on and adds features to DX10 capability."aren't you contradicting yourself? :)
chizow - Saturday, January 31, 2009 - link
Oh right, that should read nothing new with regards to hardware requirements. They could've just as easily added the features and called it DX10a or DX10.2 etc....FesterSilently - Saturday, January 31, 2009 - link
Hrm...all I really pulled from this article was:- "...the rejection of Vista" pg. 1
- "...no one knew how much Vista would really suck" pg. 2
- "...slow adoption of Vista" pg. 3
- "...ends up being a more expensive Vista in a shiny package" pg. 3
- "...because of Vista's failure" pg. 7
- "...as Vista still sucks" pg. 8
- "...better upgrade option for XP users than Vista" pg. 8
Oh, yeah! And:
- "...DX 11 looks to rawk" (my quote)
Well.
I'm glad we cleared all that up. Now where's that XP disk...?
:/
ssj4Gogeta - Saturday, January 31, 2009 - link
Sorry for posting this again, but Derek, have we had any more news on Larrabee? Weren't the first samples supposed to be ready by the end of 2008?I also read somewhere that Intel bought Project Offset to use their technology in the launch title for Larrabee.
scruffypup - Saturday, January 31, 2009 - link
Interesting there is still the bashing on Vista,..Some say it "sucks"
Answer this:
Does Vista do everything Xp does? YES
Does Xp do everything Vista does? NO
So how can you say Vista sucks in comparison to XP? The driver issue? That has happened on most releases of Microsoft operating systems and is not the fault of the operating system? The fact old software does not always work on it? That again is not the operating system fault,.. the software was written for a certain operating system,...
Security? I think we all know that Vista is inherently more secure
Performance? Does a new software package (OS, driver, game) always mean better performance,... most often NO!!! GAMES especially,.. they do more,... but are bigger resource hogs,... most drivers you can say the same,...
I feel that Derek's article was unprofessional and filled with a bias which will lead me to steer clear of his future articles,... and ESPECIALLY any opinions he wants to chime about,... sorry to see the Anandtech site have such "craptacular" articles that "suck"!!!
MightyDrunken - Wednesday, February 4, 2009 - link
To love or hate Vista - either way is an opinion. For me there is no correct answer regarding Vista. If the article writer is not allowed an opinon which disagrees with some of it's readers then AnandTech articles will be worthless.I use Vista daily and my impression is it sucks, sorry.
On a two year old dell its slow, very slow(2 Gig RAM, Dual Core duo). All drivers are up to date. My slower windows XP machine was much faster.
The only improvements with Vista I notice are the breadcrumb trail in Explorer and search on the start menu.
Those improvements are not worth 13+ gigs of files and a fairly recent computer. Someone will pipe up and say, "Oh but hard drives are cheap", but what if I want to backup my install to DVD, memory stick...?
Vista is pure bloat. Lets hope the Windows 7 hype is not as misleading as Vista's hype before release.
epyon96 - Saturday, January 31, 2009 - link
Suffice to say the article does not have the flair of Anand Shimpi but it was educational. The Vista comment was unnecessary and seemed out of place.You kept emphasizing how Dx11 is a superset of Dx10. I am wondering why Microsoft just named it Dx10.2 or something of that nature to indicate the superset nature of it? What is the fundamental difference between a 1 and 0.1 or 0.2 advancement in Direct X technologies.
bigsnyder - Saturday, January 31, 2009 - link
I think many of you are trying to interpret what you want to hear from his Vista comments. Bottom line, it is his article, he can say what he wants. I would say that there is far more people agreeing with his comments than what is posting here. There is no denying the fact the Vista did not live up to its hype at launch. Sure, XP had teething problems as well, but the difference here is that XP does offer a significant reason to upgrade over its predecessors win98/ME (w2k was a different market segment). Outside of DX10, what does Vista offer that I should be compelled to upgrade? Vista does not offer that same compelling reason. The current state of Vista is almost irrelevant (I'm sorry, but even with the improvements, Vista still does not paint a rosie picture). The damage is already done. Why do you think MS is accelerating Windows 7 development? Derek, thank you for your honest perspective.Intelman07 - Saturday, January 31, 2009 - link
Urgh Vista bashing from Anandtech...Vista simply does not suck.
bobvodka - Saturday, January 31, 2009 - link
Ok, lets cover a few things with one post;1) Vista "sucks".
I find this claim today intresting; 99% of those I know who have used Vista have seen it as a large improvement over XP, myself included, and those who haven't generally have low spec or unsupported hardware. I've used Win3, 3.11, 95, 98, 98SE, ME, 2K, XP, XPx64 and now Vista and out of all of them Vista has been the smoothest OS I've had from day one (this was March 2007 when I accidently killed my XPx64 install by not paying attention) with the only troubles being 3rd party drivers (such as Creative's inability to write drivers which work first time out and NV apprently forgetting how to write them for around 9months in 2007).
So, Vista far from sucks, what Vista suffers from is being bashed left, right and center even before it was released by 'tech sites' who brought into the whole 'Vista sucks' thing and continued the myth. I can only assume this is because you get better readership from saying something of MS's sucks rather than 'hey, it isn't perfect BUT...' type thing. Hey, that's journalism all over I guess.
2) Vista's development time
This was always going to be a problem for MS. XP was built upon Win2K, indeed they share the same driver model, which was built upon NT and the 9x kernel (in places) so it had a very long development history behind it. Vista had a whole new design thrown at it, new driver model, improved security model etc etc; this stuff doesn't happen quickly nor cheaply. The fact it had such a major overhall and worked so well out of the gate is nothing short of impressive.
The problem however is that many of these changes are 'under the hood'. All the end user sees is a new shiney interface and wonders 'why did this take so long?'. Now, I guess MS could have tried to explain this to the ordinary person, much like they did to technical people, however I suspect this would have been a waste of time because all average Joe User cares about is if it will run his stuff.
(side note: this is something MS really don't get enough praise for, the mindbending amount of work they put in to maintain backwards compatbility between their OS revisions. Take program written for Win95 and chances are it'll work just fine in Vista, THATS impressive.)
3) DX10 and the performance quest
This is another one of those things were people needed more information than they were given to understand whats going on here. The simple truth is, yes, DX10 allows you to write programs which use the GPU better and reduce CPU overhead (this reduction was infact a major part of the performance they were talking about, however everyone assumed when they said 'performance' they meant 'frames per second'); however this would require writing DX10 code, not naively port their DX9c code across and hope everything works out. The problem is this cost time and money, and with the major 2 consoles being DX9 level hardware (more or less) anything which needs to be crossplatform isn't going to have 'shiney DX10 renderer' high on their 'todo list'. (site note: the PS3 doesn't use OpenGL, it has an OpenGL|ES library but anyone with any sense codes to Sony's own graphics library instead).
Of course, once these DX10 renderers are done they add more things to the scene as well, be it particles or general increase in the level of detail. So suddenly you are getting more things on screen for around the same cost in many cases.
End of the day however the DX10 API IS a better API than DX9c and OpenGL; OpenGL did have the chance to 'catch up' but with the dropping of Longs Peak and the release of OpenGL3.0 they threw that away. (personal note; I'd used OpenGL since 1999, however that dropping of the ball made me move away from it).
4) DX11 on XP.
Not going to happen.
Cost and development time don't make it worth while; unless ofcourse everyone was prepared to pay $150+ for an upgrade, because it makes no financal sense to even consider doing this for free and at that cost, well, you might as well get Vista or Windows7.
5) DX11 and Multi-threading
I was at the XNA Gamefest 2008 in london and I'm 99% sure that the multithreaded stuff DOESNT require a driver update. Granted, you'll get better performance with one but the runtime itself can deal with it.
(As for who I am; I work as a programmer for a UK based games company. I wrote the chapter on GLSL for More OpenGL Game Programming and I've been coding now for over 15 years on various pieces of hardware. Just incase you felt I was some newbie :))