clipka <ano### [at] anonymousorg> wrote:
> nemesis schrieb:
> > Completely mindblowing, specially the later scenes! o_O That's why V-Ray is top
> > today, without even resorting to unbiased algorithms.
>
> Sure it's unbiased? Looks like a monte-carlo approach to me.

At least until very recently V-Ray used regular biased backwards raytracing with
photon mapping, except incredibly optimized.  Perhaps those speckles in the
video have simply something to do with the GPU calculating an insane amount of
rays and rendering pixels out of order?

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On Sun, 23 Aug 2009 21:22:17 -0400, nemesis wrote:

> clipka <ano### [at] anonymousorg> wrote:
>> nemesis schrieb:
>> > Completely mindblowing, specially the later scenes! o_O That's why
>> > V-Ray is top today, without even resorting to unbiased algorithms.
>>
>> Sure it's unbiased? Looks like a monte-carlo approach to me.
> 
> At least until very recently V-Ray used regular biased backwards
> raytracing with photon mapping, except incredibly optimized.  Perhaps
> those speckles in the video have simply something to do with the GPU
> calculating an insane amount of rays and rendering pixels out of order?

IIRC, the ray depth was only set to 5 in those videos, wasn't it?

Jim

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clipka wrote:
> ... and that space where /something/ was before.

Oh yeah. I guess I was thinking too much of the static scenes they showed 
and not enough about actual, you know, video games. :-)

Hey! Myst!  ;-)

-- 
   Darren New, San Diego CA, USA (PST)
   Understanding the structure of the universe
    via religion is like understanding the
     structure of computers via Tron.

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Jim Henderson <nos### [at] nospamcom> wrote:
> On Sun, 23 Aug 2009 21:22:17 -0400, nemesis wrote:
>
> > clipka <ano### [at] anonymousorg> wrote:
> >> nemesis schrieb:
> >> > Completely mindblowing, specially the later scenes! o_O That's why
> >> > V-Ray is top today, without even resorting to unbiased algorithms.
> >>
> >> Sure it's unbiased? Looks like a monte-carlo approach to me.
> >
> > At least until very recently V-Ray used regular biased backwards
> > raytracing with photon mapping, except incredibly optimized.  Perhaps
> > those speckles in the video have simply something to do with the GPU
> > calculating an insane amount of rays and rendering pixels out of order?
>
> IIRC, the ray depth was only set to 5 in those videos, wasn't it?

hmm, but they appear even when there's no glass around. ;)

It cleans up pretty quickly anyway.  Ok, not yet there for games, but for
real-time architectural visualization, this is nuts.  Can only wonder some GPU
iterations ahead... XD

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On Sun, 23 Aug 2009 22:23:07 -0400, nemesis wrote:

>> IIRC, the ray depth was only set to 5 in those videos, wasn't it?
> 
> hmm, but they appear even when there's no glass around. ;)

Yeah, true....

> It cleans up pretty quickly anyway.  Ok, not yet there for games, but
> for real-time architectural visualization, this is nuts.  Can only
> wonder some GPU iterations ahead... XD

Well, and one thing from the demo was that the card in use was described 
as "not the high-end option" (words to that effect).

Jim

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nemesis schrieb:
> At least until very recently V-Ray used regular biased backwards raytracing with
> photon mapping, except incredibly optimized.  Perhaps those speckles in the
> video have simply something to do with the GPU calculating an insane amount of
> rays and rendering pixels out of order?

Well, maybe they're artifacts of the photon mapping; that would appear 
to be quite fitting.

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Jim Henderson schrieb:
> Well, and one thing from the demo was that the card in use was described 
> as "not the high-end option" (words to that effect).

I actually happen to have that same GPU (GeForce 285) in my machine. I 
went for that particular graphics card /because/ I didn't intend to get 
the heaviest weapon out there, rather just some decent graphics power 
for a decent price (something to do some fluent Wings3D or Poser work 
with) - so I guess there's heavier artillery /already/ in both the 
gamers' and CG professionals' arsenals.

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clipka wrote:
> nemesis schrieb:
>> At least until very recently V-Ray used regular biased backwards 
>> raytracing with
>> photon mapping, except incredibly optimized.  Perhaps those speckles 
>> in the
>> video have simply something to do with the GPU calculating an insane 
>> amount of
>> rays and rendering pixels out of order?
> 
> Well, maybe they're artifacts of the photon mapping; that would appear 
> to be quite fitting.

They're artifacts of forward based monte-carlo GI.

The idea is something along the lines of, every time you need to take a 
light sample, you just shoot one randomly (rather than POV's method of 
using many surrounding samples) and deal with it.  Thus, the speckles.

The next step is to re-render the scene, and average the results with 
the previous.  For this reason, images rendered in this manner show a 
full scene quite quickly but with horrible quality, while the longer you 
leave them running the more they resolve into high quality images.

You can see this in the video as things get really crappy when they move 
the camera, and resolve into higher quality when they don't.

...Chambers

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> Let's use the GPU to speed up POV-Ray!
>
> http://www.cgarchitect.com/news/SIGGRAPH-2009-CHAOS-GROUP-GPU.shtml

If that's MCPov quality output (it's hard to tell from that video alone) 
then it's pretty awesome speed.  The models used in the video there are 
pretty huge in terms of triangle-count, it seems they have a pretty 
efficient GPU GI renderer there :-)

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> They're artifacts of forward based monte-carlo GI.
> 
> The idea is something along the lines of, every time you need to take a 
> light sample, you just shoot one randomly (rather than POV's method of 
> using many surrounding samples) and deal with it.  Thus, the speckles.
> 
> The next step is to re-render the scene, and average the results with 
> the previous.  For this reason, images rendered in this manner show a 
> full scene quite quickly but with horrible quality, while the longer you 
> leave them running the more they resolve into high quality images.
> 
> You can see this in the video as things get really crappy when they move 
> the camera, and resolve into higher quality when they don't.

Maybe now we'll start seeing games with a "night vision mode" that 
actually works the same way as real night vision? (I.e., not just a 
normal render pass with a noise filter applied afterwards.)

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