47bd77a2$1@news.povray.org...

> But then, as you know, most of my renders are pretty trivial. For example, 
> the image attached to the first post in this thread. I have no idea how 
> the hell it's possible to model something that complicated. Surely 
> something like that must take many months of modelling?

More likely a few hours. We're not in the early 90s anymore. Modelling apps 
have come a long way.
Now have a look at the images below for some state-of-the-art rendering.
http://thirdseventh.cgsociety.org/gallery/573528/
Note that this is done with VRay, which is not an unbiased renderer, but a 
"traditional" raytracer with GI and *** lots *** of improvements. 
http://www.cgarchitect.com/news/Reviews/Review007_1.asp

G.

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- POV-Ray and Poser computer images
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>> But then, as you know, most of my renders are pretty trivial. For example, 
>> the image attached to the first post in this thread. I have no idea how 
>> the hell it's possible to model something that complicated. Surely 
>> something like that must take many months of modelling?
> 
> More likely a few hours. We're not in the early 90s anymore. Modelling apps 
> have come a long way.

People have moddeling apps now? Damn, I just type everything in as text...

[Only kidding!]

> 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... :-(

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

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> Right. So trace rays, let them bounce off diffuse surfaces at
> semi-random angles, and gradually total up the results for all rays?

Basically yes. Although there are many ways to reduce the amount of rays needed
to achieve certain noise level without affecting "unbiasness". The point is
that the rays keep on going without stopping them artificially.

> Presumably that won't work with point-lights though? (You'd never hit any!)

There are no point light sources in real life. They always have some volume.
Even a small one. But as mentioned, there are methods to allow them and also
speed up rendering. Like bidirectional path tracing.

For the same reason path tracing works well for outdoor scenes. See image
section for an example.

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Severi Salminen wrote:
>> Right. So trace rays, let them bounce off diffuse surfaces at
>> semi-random angles, and gradually total up the results for all rays?
> 
> Basically yes. Although there are many ways to reduce the amount of rays needed
> to achieve certain noise level without affecting "unbiasness". The point is
> that the rays keep on going without stopping them artificially.

Right. Well presumably there must be *some* limit on the maximum 
recursion depth though?

>> Presumably that won't work with point-lights though? (You'd never hit any!)
> 
> There are no point light sources in real life. They always have some volume.

Yes indeed...

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

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On Thu, 21 Feb 2008 11:53:40 +0000, Stephen wrote:

> On 20 Feb 2008 15:09:52 -0500, Jim Henderson <nos### [at] nospamcom> wrote:
> 
> 
>>I've seen photos that don't look photorealistic to me.  It most
>>certainly is a matter of opinion.
> 
> 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. :-)

Jim

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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?

Jim

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Warp escribió:
> John VanSickle <evi### [at] hotmailcom> wrote:
>> How long do you have to wait before the graininess has reliably become 
>> unnoticeable?
> 
>   I wonder if an automatic measurement and then a threshold couldn't be
> developed. For example, if a given pixel hasn't changed color for the
> last n rays which have affected that pixel, then that pixel is done.
> When all the pixels fulfill this requirement, the image is done.
> 

http://www.winosi.onlinehome.de/FAQ.htm

> Is there any stop criteria for the render process in the current
> release?
 >
> No. When the image is pretty enough in your opinion, you have to stop
> manually by selecting Render/Stop from the pulldown-menu.
 >
> I am experimenting with the local contrast as a stop criteria. It
> starts with a high value because of the noise, and if the image gets
> smoother and the noise reduces with each iteration, the local
> contrast converges to a certain end-value. Unfortunately this value
> is not known until the image is finished. So I let the renderer
> calculate the difference between the current local contrast and the
> one from the iteration before. This difference value goes to zero
> when the image has reached its final contrast after an infinite
> number of iterations. I thought to stop the renderer when it reaches
> a certain small difference value, but in practice the difference
> function is very noisy too, giving zero or even negative values very
> early. You can trace these two values during rendering in the
> File/Info-Dialog (bottom right).

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Gilles Tran wrote:
> http://thirdseventh.cgsociety.org/gallery/573528/

that is friggin' amazing.  I actually thought it was another 
render+photo montage.  well, perhaps a few parts are.

I also love the renders by artist Giraffe...


all using biased renderers.  shame there's no rendertimes...

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Jim Henderson wrote:
> On Thu, 21 Feb 2008 11:53:40 +0000, Stephen wrote:
> 
>> On 20 Feb 2008 15:09:52 -0500, Jim Henderson <nos### [at] nospamcom> wrote:
>>
>>
>>> I've seen photos that don't look photorealistic to me.  It most
>>> certainly is a matter of opinion.
>> 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.

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Invisible wrote:
> scott wrote:
> 
>> The lighting model implemented in POV is about the simplest available, 
>> what was first used on 3D cards 10 years ago.  Today there are far 
>> more accurate models used, you must have heard names like 
>> Cook-Torrence, Blinn etc, if you've never looked outside of POV you 
>> wouldn't know they existed.
> 
> That would explain how... I didn't know they existed. :-D

time to hang on forums like that of luxrender and meet yet another facet 
of reality... ;)

> (BTW, POV-Ray offers several kinds of scattering media, but I can never 
> seem to tell the difference between them. Is that normal?)

you probably haven't played with them enough, different light angles etc...

>> They start to model the microfacets on a surface and produce lighting 
>> results based on the geometry and physics of the microfacets (eg 
>> occlusion, self-shadowing etc).
> 
> So how does that affect the end visual result? Are we talking about a 
> big difference or a subtle one?

how about a practical one?

> Does it add more triangles to the areas of greatest curvature and fewer 
> to the flat areas?

you know those Pixar movies?  The renderer used, Renderman, is basically 
a scanline that breaks all geometry down to micropolygons measuring less 
than a pixel on the fly.  You only see smooth curves as the final result...

> I often look at a game like HL and wonder how it's even possible. I 
> mean, you walk through the map for, like, 20 minutes before you get to 
> the other end. The total polygon count must be spine-tinglingly huge. 
> And yet, even on a machine with only a few MB of RAM, it works.

machines evolve.  The amount of polygons going around in PS3 games or 
Crysis certainly wasn't possible just a few years ago.

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