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

Post a reply to this message

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).

Post a reply to this message

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...

Post a reply to this message

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.

Post a reply to this message

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.

Post a reply to this message

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.

Post a reply to this message

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. ;)

Post a reply to this message

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

Post a reply to this message

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

Post a reply to this message

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

Post a reply to this message