Real-Time Ray Tracing : Holy Grail or Fools’ Errand? *Partial Reconstruction*

Discussion in 'Rendering Technology and APIs' started by AlNets, Oct 18, 2007.

  1. AlNets

    AlNets ¯\_(ツ)_/¯
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    Okay, here's my attempt at bringing back *some* of the posts I could find floating about on the internet. I'll update each post as I go along i.e. 1 post = 1 page of the original thread I could find.

    I did find all of page 2... it may very well be the longest single post in B3D history.

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  2. AlNets

    AlNets ¯\_(ツ)_/¯
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    Page 2:

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  3. AlNets

    AlNets ¯\_(ツ)_/¯
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    Page 3 remnants:

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    Ignored a few posts that were OT.
     
  4. AlNets

    AlNets ¯\_(ツ)_/¯
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    Someone wanna buy me a new keyboard please? :cool:

    Here's the remains of Page 4:

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  5. AlNets

    AlNets ¯\_(ツ)_/¯
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    Ok folks, that's all I could find. Um.... happy search-reading? ;)
     
  6. Geo

    Geo Mostly Harmless
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    Thanks for your efforts, AlS. You da bomb!
     
  7. rwolf

    rwolf Rock Star
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    What an interesting article. Certainly has some excellent arguments.
     
  8. hoho

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    I have some posts sent to my e-mail that are not listed here. I wonder how could they be merged to their correct places. If I just dump them here their order will be quite bad. It would be really nice if they would go to their correct places inbetween the posts AlStrong put here.


    From the first count I have around 13 posts from the first and >10 from third page that are not here. In total I have 50 posts but many are already listed.
     
  9. Geo

    Geo Mostly Harmless
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    Put them here grouped by page and we'll at least move them to the right post above.
     
  10. hoho

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    Problem is I have no ideas where do the pages start and end :)

    I'll simply put them all in the order I have them in my inbox. That will mean many will be duplicates of what are already posted and lots of them will be missing but still better than nothing. It'll take a while to massage all these 50 posts to nice format so I have no ideas when I have them done.
     
  11. Geo

    Geo Mostly Harmless
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    Maybe just email it to me instead. geo at you-know-where.
     
  12. hoho

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    I tried to massage it into a format I could simply copy-paste to forum but somehow it didn't work and forum displayed it as plaintext. If anyone sees the mistake just let me know so Geo won't have to manually change those 50 posts :)

    The text is here together with the parser: http://hoho.bafsoft.net/rt-b3d/
     
  13. Geo

    Geo Mostly Harmless
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    http://arstechnica.com/journals/hardware.ars/2007/10/22/real-time-ray-tracing-the-gpu-and-gpgpu

    Ars weighs in, in part in response to Deano's article.

    Is it just me or is he basically saying RT = GPGPU there?

    And, Gee, Jon, that "loyal" comment stung. Why didn't you formulate it correctly and just say, "Beyond3D is loyal to the GPU, unlike right thinking folks like myself who are loyal to the CPU". We wouldn't call you an Intel fanboy! (well, at least I wouldn't).

    Edit: This new Intel article is linked in the Ars piece as well: http://blogs.intel.com/research/2007/10/more_on_the_future_of_raytraci.html If I'm not mistaken (and I may be), it basically says at the macro level that Deano's article is correct and a hybrid solution is the real way forward. Doesn't it? If so, nice to see Intel admit it.
     
  14. 3dilettante

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    Jon didn't say much about the article on B3D.

    It's little more than a one-off chance to segue into a shot at B3D's supposed collective stance on GPGPU (which he then says he won't get into).

    The concerns stated about raytracing are not really addressed, and the implication is instead made that: "B3D likes GPGPU, so the concerns about ray tracing by someone with an intimate knowledge of graphics rendering must be informed by a GPGPU bias".

    The implication is that B3D lacks the sophistication to differentiate between a debate on graphics rendering and the more varied GPGPU question.

    While I am partial to his position that Larrabee has potential to seriously challenge and possibly trump GPUs in much of scientific computing, I do not like the way his argumentation turned out.

    I'll chalk it up to the number of separate ideas he lumped into a few paragraphs. The way that blog post was structured, the theme was a somewhat indistinct mash of several possibly different and subtly interrelated ideas that can lead to excessive interpretation.

    Though I do read a little bit of the shot there at B3D for not converting so readily to the future Larrabee, and instead hewing to the known quantities of current GPU and CPU designs which currently have more of substance behind them.

    Methinks Jon protests too much for the sake of Larrabee, if only because Larrabee's supposed true proponents at Intel have a mixed history of making a cogent defense themselves.
     
  15. Tim Murray

    Tim Murray the Windom Earle of mobile SOCs
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    Yes, which is silly. Look what Mike Houston has to say about the Intel article, and Mike Houston definitely knows more about GPGPU than Jon or me. I still don't know why Jon thinks Larrabee will be immune to the biggest problems of GPGPU, unless you're talking about data structures or something. But then Mike is completely correct--you're going to get into trouble with locking and all that.

    Also, Jon seems to think that what is available in CUDA or Brook right now is it as far as your GPGPU programming model can go, and I'm pretty sure that's rubbish.

    Basically, I don't like Jon's argument about Larrabee because I can think of three ways it could be so much better than GPGPU to justify this excitement, and none of them are remotely likely. One, it could simply be that much faster. I don't think that's completely out of the question, although I seriously doubt its likelihood. Two, it somehow solves the CPU/GPU synchronization barrier. Unless each core is somewhat close to your Nehalem's cores or whatever, I have my doubts there. Maybe you're closer to an MIMD machine so you can avoid some things on the GPU that you would otherwise do on the CPU, but you're certainly not going to solve the problem. Three, you get data structures without ridiculous overhead. Three would change everything, but I think the chances of that happening are zero.
     
  16. Geo

    Geo Mostly Harmless
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    I think what Ars, and probably Intel, are missing about pieces like Deano's and our (B3D's) position on Intel and ray-tracing in general, is that we all want Intel to succeed and be a viable competitor and provider of high-end graphics solutions. All this critiquing isn't coming from a "hope they crash and burn" place. It's coming from a "listen to the voice of experience, new guy" place.

    If anything I was fairly relieved to read the new Intel research piece he pointed out, as it's much less aggressively "all RT all the time" than previous Intel messaging on the subject.
     
  17. Mintmaster

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    That was a rather useless article.

    Not only did he equate RT to GPGPU, as you said, but has no idea what the fundamental argument is here. It's not about Intel vs. GPGPU, it's about raytracing versus rasterization, and an 80 core CPU in 2010 trying to compete with a fraction of the die space of a GPU from, say, 2005.

    When people from NVidia are talking about using GPUs for raytracing, they are trying to create a new market for their products. It has nothing to do with them thinking raytracing is better than rasterization.
     
  18. Tim Murray

    Tim Murray the Windom Earle of mobile SOCs
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    Well, I don't think anyone's said that raytracing has absolutely no place at all in rendering. And it's also true that what you'd need to do raytracing better on a GPU are many of the same things that would make GPGPU better.

    But, the main points of the Intel article on the problems with GPGPU are, IMO, fairly ridiculous. I can't really imagine Intel waving their hands and "solving" the parallel data structures problem. Not that it would matter that much; unless you can keep the entirety of the data structure in some sort of cache or you can have a bajillion threads in flight at the same time, your latency from accessing pointers and such would be so great that your performance would tank anyway. And CUDA will get better, CAL will hopefully be reasonable (I haven't seen anything yet, but I'm hopeful that they'll do something good), Intel will have their own things, Brook will continue to improve (and maybe NV will open up their platform--I'd like to see that, too).

    Intel is arguing that GPGPU isn't some magic bullet, but nobody said it's anything but an accelerator. Jon seems to be arguing against its use as a magic bullet as well and then dragging raytracing into the mix (which, having looked at his Larrabee article again, he doesn't understand). I have nothing but respect for him when it comes to CPUs and general architecture stuff, but I don't think he really gets the software side of massively parallel programming. I mean, we're basically talking about extremely active research topics in CS...
     
  19. Dee.cz

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  20. ShootMyMonkey

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    Except for the fact that it doesn't. Note the bolded part.

    All the so-called realtime global illumination methods are just too limited to be of any use in practice in actual games. They work in confined spaces with few lights (typically short-range local lights), small scenes of relatively few elements, scale poorly with scene complexity (particularly when number of dynamic objects grows), rely heavily on a priori knowledge (whether by precomputation or hand-placed markups), and without exception, have failure cases which are all too common in real world usage.

    There are plenty of tricks out there we all use to get GI-ish effects in realtime, and they work beautifully for the limited range of cases that they're capable of solving. Step outside of that just a little bit, and all bets are off.
     

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