Invisible wrote:
> scott wrote:
>> The one I remember has a bronze vase, and repeatedly compares the 
>> different algorithms to a photo.  It's surprising how tiny changes in 
>> the highlight can make you believe it's really bronze or plastic or 
>> some unrealistic material.
> 
> Right. So we're talking about something so subtle that I'm unlikely to 
> notice any difference...

That's not what he said, but yeah, you probably won't notice anything.
Normal people will.

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Jim Henderson wrote:
> On Thu, 21 Feb 2008 09:44:11 -0300, nemesis wrote:
> 
>> Invisible wrote:
>>> nemesis wrote:
>>>> I want povray to evolve.  Being provocative is a way to do that.
>>> No - being provocative to the point of trolling is a way to get
>>> everybody to completely ignore you. ;-)
>> eventually, that kind of attitude will lead to everybody ignoring
>> povray, except for the geekiest of geeks...
> 
> Andy's right - being "provocative" (interesting use of the word) just 
> pisses people off.  Pissed off people don't listen.
> 
> After all, in the religion discussion, I was being provocative and you 
> ran off.  More or less proves the point, don't you think?

yes, it pisses people off and they'll ignore you, for a time.  But the 
damn thing will echo in their heads and eventually they'll do something 
about it. ;)

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Invisible <voi### [at] devnull> wrote:
> Does anybody, anywhere, have any details of how the algorithm actually 
> works? As in, how is this different to a normal ray tracer?

  A BRDF is a function between incoming light (from all possible directions)
and outcoming light (to all possible directions).

  In other words (in an ideal case), at each point light coming from all
possible directions are taken into account, and this light can be reflected
to all possible directions, with a factor given by the BRDF function.

  Naturally in order to calculate this you would have to shoot an infinite
number of rays from each point, and when those rays intersect other surfaces,
again an infinite amount of rays would have to be sent from those points,
ad infinitum.

  In practice this is, of course, impossible. However, brute force renderers
try to approximate this by simply sending rays at random directions, lots
and lots of them. The more rays are sent, the more the final results
approaches the optimal. This results in a very grainy image at first,
because the amount of samples is not even nearly enough. However, as more
and more rays are traced, the result starts slowly approaching the ideal.

  When the BRDFs are properly designed to simulate the behavior of
real-world materials, the results can be quite realistic.

  Or this is how I have understood it.

  POV-Ray's stochastic global illumination resembles this, although it's
quite limited (and doesn't use BRDFs).

-- 
                                                          - Warp

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On Thu, 21 Feb 2008 14:40:25 -0300, nemesis wrote:

>>> As an aside is a black and white photograph, photorealistic, or a
>>> sepia one? Are the Pre-Raphaelites or chocolate box paintings?
>> 
>> You read my mind, Stephen. :-)
> 
> yes, they are all actual light (photo) captures, just lacking enough
> resolution or colors.

But a binary diff would be different against those.

So it is subjective after all....

Jim

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On Thu, 21 Feb 2008 14:58:09 -0300, nemesis wrote:

> Jim Henderson wrote:
>> On Thu, 21 Feb 2008 09:44:11 -0300, nemesis wrote:
>> 
>>> Invisible wrote:
>>>> nemesis wrote:
>>>>> I want povray to evolve.  Being provocative is a way to do that.
>>>> No - being provocative to the point of trolling is a way to get
>>>> everybody to completely ignore you. ;-)
>>> eventually, that kind of attitude will lead to everybody ignoring
>>> povray, except for the geekiest of geeks...
>> 
>> Andy's right - being "provocative" (interesting use of the word) just
>> pisses people off.  Pissed off people don't listen.
>> 
>> After all, in the religion discussion, I was being provocative and you
>> ran off.  More or less proves the point, don't you think?
> 
> yes, it pisses people off and they'll ignore you, for a time.  But the
> damn thing will echo in their heads and eventually they'll do something
> about it. ;)

Ah, so you've decided Darren and I were right after all, then? ;-)

Jim

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Jim Henderson wrote:
> Ah, so you've decided Darren and I were right after all, then? ;-)

I've come to the conclusion that I would be terribly disappointed if the 
universe and/or life actually were designed by an intelligence. All the 
awe and wonder would just turn into "oh, he meant it that way."

Kind of like watching an amazing speed-run, only to find out they did it 
on God mode or something.  What would be the point of living in such a 
place?

-- 
   Darren New / San Diego, CA, USA (PST)
     On what day did God create the body thetans?

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On Thu, 21 Feb 2008 11:17:00 -0800, Darren New wrote:

> Jim Henderson wrote:
>> Ah, so you've decided Darren and I were right after all, then? ;-)
> 
> I've come to the conclusion that I would be terribly disappointed if the
> universe and/or life actually were designed by an intelligence. All the
> awe and wonder would just turn into "oh, he meant it that way."
> 
> Kind of like watching an amazing speed-run, only to find out they did it
> on God mode or something.  What would be the point of living in such a
> place?

:-)

Jim

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Invisible wrote:

>> Now have a look at the images below for some state-of-the-art rendering.
>> http://thirdseventh.cgsociety.org/gallery/573528/
> 
> Sorry - due to my extremely lame monitor at work, most of these come out 
> nearly black... :-(

OK, now I can view these on a decent monitor... Mmm, yes, that's pretty 
damn impressive. I'm not too keen on the slightly fuzzy "I'm using a 
real camera lense" effect. But other than a few dark areas which seem a 
tad noisy, these all look pretty damn real to me...

[Oh, and the bark on that tree.]

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Darren New wrote:

> I've come to the conclusion that I would be terribly disappointed if the 
> universe and/or life actually were designed by an intelligence. All the 
> awe and wonder would just turn into "oh, he meant it that way."
> 
> Kind of like watching an amazing speed-run, only to find out they did it 
> on God mode or something.  What would be the point of living in such a 
> place?

Mmm. I'll have to remember that one...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Warp wrote:

>   A BRDF is a function between incoming light (from all possible directions)
> and outcoming light (to all possible directions).
> 
>   In other words (in an ideal case), at each point light coming from all
> possible directions are taken into account, and this light can be reflected
> to all possible directions, with a factor given by the BRDF function.
> 
>   Naturally in order to calculate this you would have to shoot an infinite
> number of rays from each point, and when those rays intersect other surfaces,
> again an infinite amount of rays would have to be sent from those points,
> ad infinitum.
> 
>   In practice this is, of course, impossible. However, brute force renderers
> try to approximate this by simply sending rays at random directions, lots
> and lots of them. The more rays are sent, the more the final results
> approaches the optimal. This results in a very grainy image at first,
> because the amount of samples is not even nearly enough. However, as more
> and more rays are traced, the result starts slowly approaching the ideal.
> 
>   When the BRDFs are properly designed to simulate the behavior of
> real-world materials, the results can be quite realistic.
> 
>   Or this is how I have understood it.

OK. Thanks.

>   POV-Ray's stochastic global illumination resembles this, although it's
> quite limited (and doesn't use BRDFs).

Also doesn't recompute irridescence at each point, but reuses samples 
from nearby points [in an effort to reduce the insane number of ray 
intesection tests required]. Hence all that parameter-fiddling business.

As best I can tell, the algorithm described just sounds like POV-Ray's 
radiosity with an infinitely low error_bound. (I.e., always resample.) 
But applied to *all* terms, not just diffuse illumination...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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