One Last Thing and Closing Thoughts
The final bit of DX11 we'll touch on is the update to HLSL (MS's High Level Shader Language) in version 5.0 which brings some very developer friendly adjustments. While HLSL has always been similar in syntax to C, 5.0 adds support for classes and interfaces. We still don't get to use pointers though.
These changes are being made because of the sheer size of shader code. Programmers and artists need to build or generate either a single massive shader or tons of smaller shader programs for any given game. 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. For instance, there is no need for memory management (because there are no pointers) or constructors / destructors in HLSL. Tasks like initialization are handled through updates to constant buffers, which generally reflect member data.
Aside from the programmability aspect, classes and interfaces were added to support dynamic shader linkage to combat the intricacy of developing with huge numbers of resources and effects. Dynamic linking allows the application to decide at runtime what shaders to compile and link and enables interfaces to be left ambiguous until runtime. At runtime, shaders are dynamically linked and based on what is linked all possible function bodies are then compiled and optimized. Compiled hardware-native code isn't inlined until the appropriate SetShader function is called.
The flexibility this provides will enable development of much more complex and dynamic shader code, as it won't all need to be in one giant block with lots of "ifs", nor will there need to be thousands of smaller shaders cluttering up the developers mind. Performance of the shaders will still limit what can be done, but with this step DirectX helps reduce code complexity as a limiting factor in development.
With all of this - the ability to perform unordered memory accesses, multi-threading, tessellation, and the Compute Shader - DX11 is pretty aggressive. The complexity of the upgrade, however, is mitigated by the fact that this is nothing like the wholesale changes made in the move from DX9 to DX10: DX11 is really just a superset of DX10 in terms of features. This enables the ability for DX11 to run on down-level hardware (where DX11 specific features are not used), which when combined with the enhancements to HLSL with OOP and dynamic shader linking mean that developers should really have fewer qualms about moving from DX10 to DX11 than we saw with the transition from DX9. (Of course, that's nothing new: the first DX8 games shipped when DX9 was out, and it wasn't until DX10 that we saw a reasonable number of DX9 titles.)
To be fair, the OS upgrade requirement also threw a wrench in the gears. That won't be a problem this time, as Vista still sucks but will be getting DX11 support and Windows 7 looks like a better upgrade option for XP users than Vista. Developers who haven't already moved from DX9 may well skip DX10 altogether in favor of DX11 depending on the predicted ship dates of their titles; all signs point to DX11 as setting the time frame when we start to see the revolution promised with the move to DX10 take place. Developers have had time to familiarize themselves with the extended advantages of programmability offered by DX10, coding for DX11 will be much easier though OOP constructs and multi-threaded support, and if the features don't entice them, the ability to run on down-level hardware with a better coding environment might just seal the deal.
I'm still an OpenGL developer at this point, and I've dabbled a bit with DirectX at times. But DirectX 11 (and my disappointment with OpenGL 3.0) mark the first time I think I might actually make the switch. The first preview of DX11 is already available in the latest DX SDK. When I've got time I'll have to download it and get started. Hopefully the implementation is as attractive as the pitch. Wish me luck.
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epyon96 - Sunday, February 1, 2009 - link
That's very insightful. Can you go into more detail?I am confused because there appeared to be significant differences between Dx9C and Dx9B since NVidia made it sound like the difference was like the difference between Dx8.1/2/3 and Dx8.4 which did seem very significant if memory serves me right.
The difference between 8.4 and 9 seemed minimal in quality of the final output.
GourdFreeMan - Monday, February 2, 2009 - link
The guidelines I spoke of were mentioned on the MSDN Forums circa 2003 regarding how changes to Direct3D would affect DirectX versioning, but seem to have been abandoned in favor of the bimonthly SDK updates following the DX 9.0c release. Bimonthly updates led to faster bug fixes, which in prior versions of DirectX sometimes required a letter update.If you are interested in the exact technical changes between DirectX versions, I suggest downloading the old SDK versions prior to the move to bimonthly updates and looking at the Changes section of the documentation.
Regarding the move between DirectX 8 and DirectX 9, Shader Model 2.0 was introduced making way for games such as Far Cry (admittedly Far Cry was a DX 9.0b game, but the changes from 9.0 to 9.0b mainly involved SM 2.0a and SM 2.0b which for Far Cry meant enhanced performance on ATi and nVIDIA cards). Far Cry would later be patched to support DX 9.0c and SM 3.0, adding features like HDR, but I would argue that the unpatched game still looked considerably better than DX8 titles.
(Incidentally there is no DirectX 8.3 and 8.4 -- there was 8.1a and 8.1b in the progression instead).
epyon96 - Saturday, January 31, 2009 - link
I wish the article had more background on what you just hypothesized (obviously with some substantiated facts) instead instead of the unnecessary vista bashing. It wound satisfy an actual curiosity.I remember that's one of the reasons why the in depth analysis of the development cycle of R770 was so well liked.
gamerk2 - Saturday, January 31, 2009 - link
The issue with DX11 is this: You need to supply a DX10 codepath for those who won't update GFX cards (you can't release a game no one has hardware for), but also would need a DX9 codepath for XP.Why would anyone release a game with three seperate grpahics code paths? Its for that reason I see a slow use of DX11, as long as XP holds 15-20% market share.
ltcommanderdata - Saturday, January 31, 2009 - link
If I remember those OS market share reports correctly, as of the end of last year Windows XP had about 65% market share, Vista has about 20% after 2 years, and Mac is nearing 10%. Even if Windows 7 is a roaring success, XP just has too much built-up market share to disappear overnight, so XP and DX9 compatibility will be required for at least another 2 years. The other thing that works against Windows 7 is that even if it isn't released until next year, it's introduction looks to be right in the middle of this economic recession, since things probably won't really pick up until late 2010 or 2011. When the economy does pick up again, there will be huge demand as companies finally switch from XP which would be 10 years old by then, but the first year of Windows 7 sales will probably be slow.bobvodka - Saturday, January 31, 2009 - link
Well, to be fair, you don't have to have a DX10 path and a DX11 path as such. A few important features work on DX10 cards anyway, such as the multi-threaded rendering stuff, so you need a DX11 and a DX9 path at most; you just have to do some feature detection to find out if you are on a DX11, DX10 or DX10.1 card.Still a slight pain, but not as much as 3 real code paths.
DarkMadMax - Saturday, January 31, 2009 - link
And main reason is consoles. There are practically no PC exclusives anymore among large budget titles (e.g. the ones who concentrate on graphics) . So all games target xbox360 hardware (if they dont they are ps3 exclusives). So until new generation of consoles appears there will be no progress in graphics. Periodhaukionkannel - Saturday, January 31, 2009 - link
To me, this article mostly talks about new features of DX11 and that some fundamental fealtures can benefit allso dx10 and dx10.1 hardware...To me it seems that the Vista part was only there to say why there are not any real DX10 games now, even the features are there. I didn't read it as an Vista hate like many people here seems to think of it.
All in all it was very good article abou how DX11 can allow those promises that DX10 promised to flourish better this time.
scruffypup - Saturday, January 31, 2009 - link
That though this article was supposed to be about DirectX 11, Derek's bias and opinion about Vista overshadowed the subject of the article,...This article shows poor writing at its finest,.. afterall doesn't writing 101 teach one to make the article about the subject you are writing about and not something else?
Again I say,... Derek does a disservice to anandtech with this bias. If you want to put in your bias towards an unrelated subject,.. at least show clearly the links (relevancy) to your intended subject material and how you come by a conclusion to support that claim other than just spouting off needlessly,... for that is what you have done essentially, as it held no relevance to the subject material the way you wrote the article.
chizow - Saturday, January 31, 2009 - link
Article summary:1)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.
2)Vista and DX10 sucked because no one wanted to use them.
Derek, like many others I disagree with your assessment of Vista's importance in the overall OS hierarchy, here's just a quick list:
1) First OS to bring 64-bit support to the mainstream.
2) First OS to offer multi-threaded driver improvements. Look at Rel 180 and 8.12 Hot Fix, where multi-threaded drivers are all the rage.
3) First OS to offer DX10 support. We're finally seeing some of the performance benefits we were promised in DX10 with multi-threaded drivers and improved AA with reading of the multi-sample depth buffer.
4) Much better OS stability compared to XP. It wasn't always the case, but contrary to your article, most of the problems were fixed in July/August with the various video hot fixes (Ryan Smith can probably confirm or deny this).
I think Win7 just emphasizes how good Vista is, and how many light years ahead both are compared to XP. You could say Win7 is like Mojave SE, not Vista SE, as you can clearly see all the Vista-haters who are running Win7 glowing about all the features and stability they've missed out on for at least a year (since Vista SP1).