What *exactly* is the cost of Xenos AA?

Discussion in 'Consoles' started by Shifty Geezer, Oct 18, 2005.

  1. ERP

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    Just changing the subpixel offset frame to frame.
     
  2. Tap In

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  3. Brimstone

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    I find almost impossible to believe that RARE, a first party of Microsoft which probably had the earliest possible developer kits with Xenos (Alpha), has failed to design their graphic engine for Perfect Dark Zero to take advantage of tiling. Now they may be struggling to get a bug free build with it working, but I'm confident by the time Perfect Dark Zero goes gold, they will have tiling up and running.
     
  4. AlBran

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    Thanks again, ERP.

    I hope so too...otherwise, that's a kick in the balls. :mad:



    I wonder if the lead programmer and others are sick of learning new architectures every year (first GCN, then Xbox, then Alpha kits, then Beta Kits). :wink:
     
  5. scooby_dooby

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    well that about settles that!

     
  6. dukmahsik

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    i actually like some form of baseline standards like such
     
  7. Carl B

    Carl B Friends call me xbd
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    DarkFalz's post on the matter assists in clearing the air on the issue - a definite plus that he posted on the matter. But it still represents some backpeddling from the original stated goals.

    Now, I think it's good that MS is being more flexible with what devs are allowed to do in terms of effects and resource useage, but phrases like "adding predicated tiling to any 3d graphics engine is pretty trivial," still stand out at me.

    It's been known for some time - or at least generally agreed - that Xenos is capable of 'virtually' free AA on a hardware level. But in the end, the question remains what will it require in terms of effort for devs to take advantage of this, and what will the ramp-up time be in terms of months/years before we start seeing it flex it's muscles in terms of game development? Will it be something that only shows up in AAA titles? Will it be absent from cross-console games? Or will it be truly ubiquitous come a certain point?
     
  8. pakpassion

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    this topic has been discussed to the max. in the last generation splinter cell 1 had alot of Aliasing compared to splinter cell 2 which had more than splinter cell 3 on xbox. as developers get to know the hardware the aliasing will diminish further.

    Further we have to see that when a game is applying HDR, alot of bandwidth is used and is used to such an extent that the AA has to be lowered. Kameo uses 2xAA while using HDR, PDZ aparently utilises HDR in some aspects but has turned off AA which is surprising because Kameo has more effects than PDZ. Maybe there is some coding ineffeciencies.

    Another example we have to see is Project Gotham Racing 3. It is applying AA and HDR at the same time and I believe its because of direct3d compression technique which was discussed a few months ago in the Chip conference where Cell and Xbox 360 Chip pictures were shown for the first time. I remember reading that if the developer did Direct3d compression, the bandwidth between the memory and the GPU would essentially be doubled. not that it WOULD be doubled but the compression works in such a way that if the bandwidth of 22.4 was doubled. it would account for what is carried from the GPU to the Memory when the compression is applied. I believe with that technique. project gotham racing is utilising full HDR and full AA at the same time. Alot of other games are applying full AA . Top Spin 2 is an example. Chrome hounds with HDR is another example. Call of Duty 2 has Bloom effects and Full AA in the final videos.

    It depends on the developer. topic closed.
     
  9. aaaaa00

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    Tiling wasn't implemented until the Beta kits. Before that there was a software emulation, but it wasn't really usable for anything but experimenting and debugging.
     
  10. scatteh316

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    It cost's 1,00000999,0000000,00000000% of performance. :p
     
  11. scatteh316

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    Could PS3 use a simular technique to maybe double the bandwidth between Cell and RSX???
     
  12. one

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    Why couldn't they get some engineering samples from ATi? They said 720p and AA are must in public, didn't they?
     
  13. Brimstone

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    I'm guessing a few programmers at RARE should be sort of familar with the concept since tiling was implemented on the Gamecube correct? Dave's Xenos article mentions that Flipper does share some concepts as Flipper, though Xenos was designed by a different set of engineers.


    If Perfect Dark Zero shipped without "tiling", how big of a patch to download would it be to change the engine into a tiler?
     
  14. pipo

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    I'd be very surprised if they would even consider such a thing. They'd better delay the game until xmas then.
     
  15. Shifty Geezer

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    Many thanks for this post. So ignoring tiling which applies whenever the framebuffer requirements exceed eDRAM capacity, and that can happen with or without AA, there is no extra Vertex pass or the like needed for AA. There is like the ordinary no-AA rendering a single sample per pixel rendered. The amount of vertex shader and pixel shader instructions executed is the same regardless of whether AA is on or off.

    Is that right?
     
  16. Dave Baumann

    Dave Baumann Gamerscore Wh...
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    How Xenos's AA works is already in the article and I've reiterated it here.
     
  17. Shifty Geezer

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    Thanks for the link Dave. That was posted recently here somewhere too :oops: So in terms of what's needed on top of rendering without AA, the answer is next to nothing other than the tiling costs. Case closed.
     
  18. RobHT

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    Nice find. Great stuff!
    I guess we can infer from this that while building a new game with predicated tiling in mind is 'trivial', retrofitting to a game further in development is non-trivial.
    If UE3 games all lack AA, well that's a bummer.

    packpassion,
    Where did you get this info? Not doubting you, just curious.
    If true, this truly closes the book on this issue, in my mind. It would mean many/most of these early titles are already incorporating some form of AA. PDZ certainly deserves a pass on this one, considering all the iterations it has been through.
     
  19. Carl B

    Carl B Friends call me xbd
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    Well the primary question though isn't so much whether or not the AA is 'free' in hardware per se, since we know it more or less is; rather what is the performance hit associated with implementing it. Now, since that question has already more or less been answered in this thread, I'm not going to harp on it - but just want to make sure that the purpose of this thread remains differentiated from the usual 'How does Xenos work' threads. :)

    Previous threads and answers have dealt mainly with the hardware implementation - this thread seems focused on the estimated performance penalties on the holistic level.
     
  20. Crazyace

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    If you had to tile your buffers - and your geometry get's very complex this is going to have an effect..

    Say for 100MVert/s ( Maybe 200 MTriangles.. ) with xyz(fp16), rgba(8) and ST(fp16) you need a max B/W of 1.4GB/s from ram to feed the triangle set up engine.

    For procedual data generated from the CPU this may come directly from the L2 core when tiling isn't enabled... but with tiling the CPU would have to write 1.4GB -> memory ( rather than directly to the gpu ), and the gpu read that 1.4GB every pass.. There is bound to be an effect ;)

    It's an extreme case.. but show's that some extra planning may be required from game programmers to reduce system load..
     
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