Digital Foundry Article Technical Discussion Archive [2011]

Discussion in 'Console Technology' started by user542745831, Dec 31, 2010.

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  1. corduroygt

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    There is no such thing in the PS3 version.
     
  2. Gitaroo

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    does MLAA also free up the fillrate on the RSX from MSAA? Since its being handle by the CPU instead. If so then it could be a great resource saving for the RSX. Can't wait to see the phyre engine 3 with the new take on MLAA.
     
  3. TheAlSpark

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    The ROPs can do 2 samples per cycle, so the main gain is memory and bandwidth. If they're doing a depth-only pass, they'll be gaining back performance there because it'll be double z-rate.
     
  4. (((interference)))

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    Yea, they didn't mention anything about it in the DF analysis either.

    Anyway, even if A2C gives you better results than conventional alpha testing when using MSAA - it doesn't really apply here, since the 360 isn't using any AA at all, making it look worse than the PS3 which also doesn't have any AA but is not using A2C (as shown in the pics)
     
  5. Cyan

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    I am playing Toy Story 3 lately, on the 360, and the game has God Rays. You can see it here (I edited the link so you can go directly to the specified minute and seconds, at 3:25 or so)

    http://www.youtube.com/watch?v=gPGwVQtXhAA&hd=1#t=03m25s

    This is a pic from Gears of War 1. I wonder if that's God Rays.

    [​IMG]

    These are real life God Rays, I took these photos today at 5PM or so, while driving.

    [​IMG]

    http://www4.picturepush.com/photo/a/5184282/img/5184282.jpg

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Games apply God Rays in a weird manner, pointing at the player instead of pointing at some far away place on the scenery.
     
    #585 Cyan, Mar 2, 2011
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  6. Laa-Yosh

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    God rays, light shafts, volumetric lights - different names for the same natural phenomenon. Basically, particles in the air scatter the light into every direction and thus the volume of space illuminated by the light becomes visible. Particles can be dust or water vapor or gases or anything.
    God rays are the special case when the outdoor air has lots of humidity, and the Sun illuminates it.

    Proper simulation requires volumetric rendering which is slow and unfeasible for games. There are many fake 3D solutions where transparent polygons are rendered; the geometry can even be updated dynamically, basically creating the opposite of shadow volumes.

    There are also many dynamic, but 2D versions, where scene geometry is used as a 2D mask in a radial blur kind of filter. This is very often used in movie VFX too, created in post, because it's relatively cheap and still convincing. But it's very hard if not impossible to use this for stuff like an overhead light filtered through a moving fan or such.
     
  7. Cyan

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    I haven't played a game with God Rays that are entirely convincing (though I'm seriously itching to, being gamer myself) but I did read this excerpt, which was especially awesome.

    cheers
     
  8. Neb

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    Statically placed godrays like ME games to.

    First ME game.
    http://img339.imageshack.us/img339/9010/mepc2c.jpg
    http://img169.imageshack.us/img169/866/mepc5.jpg

    Crysis, Stalker COP/CS applies godrays even if you dont look at sun. You can see mountains create godrays at distance for example in Crysis. How visible it is depends on the strength/daytime set by artist.

    There is also a strategy 3D game for PC that came out some years ago with DX10 features that had godrays being cast inbetween the clouds pretty much exactly like those pics. Really nice though I cant remember the name but it was a Swedish bigname game.

    EDIT: World in Conflict

    At 3:00.
     
    #588 Neb, Mar 3, 2011
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  9. corduroygt

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  10. Ruskie

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  11. betan

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    Great piece. I'm also glad someone finally tried SPU raytracing for occlusion culling.
     
  12. joker454

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    Is that what they are doing? I assume you meant this blurb:

    Which was really interesting, but to me that reads that they just made a software resterizer that runs on spu, and they used it to do the depth only z prepass on spu instead of gpu no?

    Good article though, it answered some questions like as to what the memory overhead to mlaa is, and why people still use bink for video.
     
  13. TheAlSpark

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    Yep. It would be the first game I've heard use a full res pass on SPUs though.
     
  14. betan

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    Yes, but how would you do ray traced culling? You only need primary rays which is just rasterization.
    The discussion came up a few years back in EDGE thread wrt triangle culling. I think the term "ray tracing" in this context is "more" self-explanatory.

    What do you think the memory overhead of mlaa is if you are already doing spu postprocessing or shading?
     
  15. Npl

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    according to the article they had to allocate the (or another) full framebuffer (2,7MB) in XDR Ram. guess it depends on what you already are doing on SPUs and whether the MLAA pass is at the end (reuse a previous buffer) or somewhere in the middle.

    I still dont get why bink is used, seems like trading off memory for bigger files is a bad idea if you have to stream assets at the same time (for which you will have less bandwidth then). Couldnt they just page out a couple MB to GDDR Ram during cutscenes...
     
  16. betan

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    I'm waiting for the nurse of MLAA to answer that, to be honest. He already implemented a tiled solution for his previous game. Since one already has to "tile" for SPU local mem, it seems more of a sync issue with RSX more than anything else.
    Very little asset streaming is happening during the cutscenes, since they are already in the memory, hence the _fast_ skip.

    I think overall, KZ3 one upped U2 in terms of streaming.
    I wish they were also as smart with multiplayer map selection.
     
  17. MJP

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    It's not full res. They rasterized depth at 640x360, then did a 16x16 downscale to 40x23 to make the buffer they used for performing the occlusion tests. Ultimately it's very similar to what DICE does for occlusion culling.
     
  18. MJP

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    You could do it very easily: shoot a ray per-pixel, see if it intersects anything. But of course it makes zero sense to do that, since rasterization will always be quicker.
     
  19. Gitaroo

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    they still didn't mention why they got SSAO in the fmv but not in game when they mention they didn't cheat to make cut scenes looks prettier.
     
  20. TheAlSpark

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    Ah, so when they say "full depth rasterization," they mean for the post-process chain, which is 640x360.
     
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