Battleforge: The First DX11 Game

As we mentioned in our 5870 review, Electronic Arts pushed out the DX11 update for Battleforge the day before the 5870 launched. As we had already left for Intel’s Fall IDF we were unable to take a look at it at the time, so now we finally have the chance.

Being the first DX11 title, Battleforge makes very limited use of DX11’s features given that the hardware and the software are still brand-new. The only thing Battleforge uses DX11 for is for Compute Shader 5.0, which replaces the use of pixel shaders for calculating ambient occlusion. Notably, this is not a use that improves the image quality of the game; pixel shaders already do this effect in Battleforge and other games. EA is using the compute shader as a faster way to calculate the ambient occlusion as compared to using a pixel shader.

The use of various DX11 features to improve performance is something we’re going to see in more games than just Battleforge as additional titles pick up DX11, so this isn’t in any way an unusual use of DX11. Effectively anything can be done with existing pixel, vertex, and geometry shaders (we’ll skip the discussion of Turing completeness), just not at an appropriate speed. The fixed-function tessellater is faster than the geometry shader for tessellating objects, and in certain situations like ambient occlusion the compute shader is going to be faster than the pixel shader.

We ran Battleforge both with DX10/10.1 (pixel shader SSAO) and DX11 (compute shader SSAO) and with and without SSAO to look at the performance difference.

Update: We've finally identified the issue with our results. We've re-run the 5850, and now things make much more sense.

As Battleforge only uses the compute shader for SSAO, there is no difference in performance between DX11 and DX10.1 when we leave SSAO off. So the real magic here is when we enable SSAO, in this case we crank it up to Very High, which clobbers all the cards as a pixel shader.

The difference from in using a compute shader is that the performance hit of SSAO is significantly reduced. As a DX10.1 pixel shader it lobs off 35% of the performance of our 5850. But calculated using a compute shader, and that hit becomes 25%. Or to put it another way, switching from a DX10.1 pixel shader to a DX11 compute shader improved performance by 23% when using SSAO. This is what the DX11 compute shader will initially be making possible: allowing developers to go ahead and use effects that would be too slow on earlier hardware.

Our only big question at this point is whether a DX11 compute shader is really necessary here, or if a DX10/10.1 compute shader could do the job. We know there are some significant additional features available in the DX11 compute shader, but it's not at all clear on when they're necessary. In this case Battleforge is an AMD-sponsored showcase title, so take an appropriate quantity of salt when it comes to this matter - other titles may not produce similar results

At any rate, even with the lighter performance penalty from using the compute shader, 25% for SSAO is nothing to sneeze at. AMD’s press shot is one of the best case scenarios for the use of SSAO in Battleforge, and in the game it’s very hard to notice. For the 25% drop in performance, it’s hard to justify the slightly improved visuals.

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  • merin - Monday, October 12, 2009 - link

    Any idea what producer I should choose if I'm getting a 5850?
    Is there even any difference between them?
    Reply
  • ambientmf - Sunday, December 06, 2009 - link

    At this point, I doubt there's much difference between vendors. Since the card is still relatively new and supply still low, I would think most vendors are sticking to the reference design.

    Warranties and support aside, they're all identical.
    I'd investigate the warranties offered, any trade-up programs (not that they'll be much to trade up from but still good to know) and any info like that.
    Reply
  • hsew - Sunday, October 11, 2009 - link

    I find it rather peculiar that even though Crysis Warhead runs better on ATI single GPUs (4890 faster than GTX275, 4870 faster than GTX260, 4850 almost as fast as GTX 260) it scales well enough in SLI to take the performance lead from ATI, as shown by the 5850 CF losing to GTX285 SLI (SLI scaling almost 100%!!). It makes one wonder just what the heck all the hype is about ATI releasing a new driver once a month if they don't seem to do make much of a difference in the performance department. Reply
  • maomao0000 - Sunday, October 11, 2009 - link

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  • cosminliteanu - Tuesday, October 06, 2009 - link


    Thanks for this kind of article, I would also to see some Fallout 3
    testing.....
    Thank you ,again :)
    Reply
  • bhougha10 - Monday, October 05, 2009 - link

    sorry the f-bomb quote was in the previous artical. But kinda adds to the point. Please no silly fan boy comments as I have stock in amd and nvidia :) (ya, in know probably silly to have stock in these two companies) Reply
  • bhougha10 - Monday, October 05, 2009 - link

    Probably get locked out of the site for saying this. But it seems like there is always an agression toward NVIDIA. Kinda like ATI gives free samples and NVIDIA does not, or not in a timely manner. I mean why would an F-Bomb be quoted on a professional site. It's not just this one statement and not just this one artical that makes me wonder.
    otherwise, as usual, great artical, with great content.
    Reply
  • Malachite - Monday, October 05, 2009 - link

    I wish you guys would put together Company of Heroes, World in Conflict and Supreme Commander so we could see clearly the differences between the cards. Today we see only reviews based on FPS, I like FPS, but my main games are all RTS.... I bought the HD4890 based on reviews but it didnt run as good as my GTX 275 for RTS titles.... Reply
  • merin - Monday, October 05, 2009 - link

    I'm wondering what the text that says "Floor @ 40.6dB" on the noise diagram means. Is it the background noise or something?

    I'm wondering if it can compete with the Sapphire HD4890 Vapor-X in the noise-department...

    "The dual slot Vapor-Chamber Cooler has a noise level under 20 dbA in 2D operation and is still under 30 dbA in 3D operation before it reaches 85 degrees Celsius." ( http://www.legitreviews.com/article/1056/1/">http://www.legitreviews.com/article/1056/1/ )
    Reply
  • Pastuch - Monday, October 05, 2009 - link

    From what I've heard at other sites the Vapor-x 4890 is significantly quieter than the ATI cooler on the 5850. Thats not a knock on the 5850, it's just that the Vapor-x cooler on the 4890 is dead quiet. I love mine. It even has HDMI, VGA, Displayport and DVI on the back of the card! Reply

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