Am 02.12.2010 13:17, schrieb Stephen Klebs:

> This makes the point very clearly. But in the particular example of the
> gradients that for me set this off was that I was trying to deal with a
> completely graphics issue: rgb 0.5 ambient 1. There is no light involved here.
> Ambient is not a real property, it is a completely artificial adjustment control
> that does not exist in the real world. Some of us are not always dealing
> necessarily with how much light is reflected off a piece of white paper in the
> real world. We just want to make a picture by telling POV give me rgb 128.

There /is/ an equivalent to "ambient" in the real world: Ambient light. 
Of course in real life it is not as uniform as in POV-Ray, but that's 
because the "ambient" mechanism was designed at a time where it was 
prohibitively time-consuming to compute ambient light from the scene 
geometry and materials (a process we call radiosity now), so the next 
best thing to do was to let the user decide how much ambient 
illumination looked convincing.

The fact that the ambient mechanism can also be used to create "non-3D 
scenes" like your gradients is just a side effect of it. It's not what 
it was originally designed for.

So yes, there /is/ light involved there. In the POV-Ray render engine, 
there is /nothing/ without light.

Post a reply to this message

clipka <ano### [at] anonymousorg> wrote:
> Am 02.12.2010 13:17, schrieb Stephen Klebs:
>
> > This makes the point very clearly. But in the particular example of the
> > gradients that for me set this off was that I was trying to deal with a
> > completely graphics issue: rgb 0.5 ambient 1. There is no light involved here.
> > Ambient is not a real property, it is a completely artificial adjustment control
> > that does not exist in the real world. Some of us are not always dealing
> > necessarily with how much light is reflected off a piece of white paper in the
> > real world. We just want to make a picture by telling POV give me rgb 128.
>
> There /is/ an equivalent to "ambient" in the real world: Ambient light.
> Of course in real life it is not as uniform as in POV-Ray, but that's
> because the "ambient" mechanism was designed at a time where it was
> prohibitively time-consuming to compute ambient light from the scene
> geometry and materials (a process we call radiosity now), so the next
> best thing to do was to let the user decide how much ambient
> illumination looked convincing.
>
> The fact that the ambient mechanism can also be used to create "non-3D
> scenes" like your gradients is just a side effect of it. It's not what
> it was originally designed for.
>
> So yes, there /is/ light involved there. In the POV-Ray render engine,
> there is /nothing/ without light.

Isn't ambient light still light? Like photons somewhere. Last time I checked
when I turned off the switch, I couldn't see anything.

Was ambient created out of convenience or out of necessity? You seem to imagine
that if we can get all our equations right for accurately describing the
behavior of light in the physical world, that somehow we will get the perfect
picture. Umph?

And what you call a "side effect". There are many ways of creating 3-D graphics.
Is POV now only for photo-realists? Csn't us fractalized unrealists play with it
too?

Post a reply to this message

> Was ambient created out of convenience or out of necessity?

It was needed to avoid shadowed parts of a 3D scene being completely black 
(which is not realistic in many real life situations).  When it was created 
hardware was not fast enough to do any more complex GI calculations, so 
adding a simple ambient term to every pixel gave a good improvement with 
little performance trade-off.

> You seem to imagine
> that if we can get all our equations right for accurately describing the
> behavior of light in the physical world, that somehow we will get the 
> perfect
> picture. Umph?

Yes, it should be perfectly identical to if you'd set up the identical scene 
in real life and taken a photo with a perfect camera.  This is the goal of 
POV.

> And what you call a "side effect". There are many ways of creating 3-D 
> graphics.
> Is POV now only for photo-realists? Csn't us fractalized unrealists play 
> with it
> too?

Sure, but don't expect the POV developers to sacrifice the core performance 
(on rendering realistically lit 3D scenes) to make it easier for various 
"side effect" to work easier.

Post a reply to this message

clipka <ano### [at] anonymousorg> wrote:

>
> No, it's your eye playing tricks on you.
>
> Our eyes are highly calibratible optical measurement tools

Sorry, hope I'm not pushing this too far but this article on filters in
photography relates to programmable cameras like POV:

"The more you learn about photography the more you'll also learn that artificial
filters and manipulation are required to make a natural looking image. Ansel
Adams realized that human perception and the photographic processes are quite
different. Therefore one needs to use a lot of filtration, manipulation and
burning and dodging to compensate for the human eye and brain's image processing
to create an image on paper that looks natural. (You can read this in his
books.) This is why most snapshots don't look like the original scene.
Artificial processes and image manipulation are needed to make a photograph look
natural.

Armchair photographers like to play a stupid game that prohibits anything
creative and requires they just play forensic photographers blindly Xeroxing
nature without filters. I only judge people on the final image, not the process.
Sadly these folks get images that are both dull and unnatural."

How to Use Filters: http://www.kenrockwell.com/tech/filters.htm

Post a reply to this message

"scott" <sco### [at] scottcom> wrote:

> > You seem to imagine
> > that if we can get all our equations right for accurately describing the
> > behavior of light in the physical world, that somehow we will get the
> > perfect
> > picture. Umph?
>
> Yes, it should be perfectly identical to if you'd set up the identical scene
> in real life and taken a photo with a perfect camera.  This is the goal of
> POV.

Well, wake me up when you get there. I really want to see that. And even if you
do get there, I'm not sure you will like what you see. I suggest you check a
little article I read on how photographers like Ansel Adams had to use filers
that I posted somewhere here.

There was similar quest years back about using computers to imitate visual
perception, that is, computers that see. And in the end, with all the variables
that couldn't be computed, like size constancy and object recognition and such,
they gave up.

Post a reply to this message

"scott" <sco### [at] scottcom> wrote:

> > And what you call a "side effect". There are many ways of creating 3-D
> > graphics.
> > Is POV now only for photo-realists? Csn't us fractalized unrealists play
> > with it
> > too?
>
> Sure, but don't expect the POV developers to sacrifice the core performance
> (on rendering realistically lit 3D scenes) to make it easier for various
> "side effect" to work easier.

I remember way back to the early POV message boards on CIS when POV was called
the "stone soup group". There were fractint people and cartoon animation people
and weird but beautiful geometric sculptors  and map-makers and glow-light
people and whomever who loved POV not just as a way of photocopying "scenes" but
as a way of using that kind of simulation to create pictures of things they
imagined that could not otherwise ever be seen. If you take a limited view, you
can't see its limited possibility.

Post a reply to this message

On 02.12.2010 12:21, Stephen Klebs wrote:
>
> I did not intend to raise such a hornet's nest here (maybe I did).

Well, your first post does sound like carping to me and nothing more. 
You are aware that you are using a BETA where things like 
backwards-compatibility-mode might very well be broken but you are even 
aware of a workaround (adding gamma 2.2 to your color definitions) but 
you cry out load "what a pain!". Sorry, but with the help of Ctrl+V I 
really do not see the pain.
And you are not able to render a scene file from 1996 with the beta. 
Well this is really bad and you claim that this has to do with the 
changed gamma handling (while this can in fact easily be fixed). But it 
has mostly to do with the used noise-generator within global_settings 
where indeed something seems not to work as expected. But investigating 
on this and making a proper bug-report seems not to be your interest anyway.
And BTW rendering this scene with POV-Ray 3.62 works perfectly fine and 
takes less than a minute on my machine. So I fail to see the need for 
multiprocessor power here.
So yes, sounds just like carping to me.


> Those in the light lab and those in the art studio.
> The difference to me is that one is trying to reproduce the behavior of light as
> faithfully as possible, the other is trying to re-create an expressive picture
> of things so that this physical input can be transformed as experienced by the
> human eye.
>
I for one completely fail to see the two fractions you are talking 
about. You always seem to imply (and you did it again within your last 
response to Christoph) that there is this "light lab" fraction that is 
completely happy when they manage to render a photo-realistic image 
showing a glass of vine and then the "art studio" people trying to 
create expressive pictures that evoke emotions.

Have you actually looked at pictures created by Christoph and Jaime for 
example? And myself? Well, I'm not satisfied with just creating real 
looking images, even this "real" is not real important to me. I know 
that I do aim for more but I also know that I do quite frequently fail 
in achieving my goals. But I'm not failing because I'm part of a "light 
lab" fraction, I'm simply failing as an artist.

And BTW have you ever considered that a great deal of well known artists 
are also known for their interest in the laws of nature?


> All these complaints, of course, are completely unfair to those in the light lab
> trying to compute the refraction of photons off a wine glass or the scattering
> of the setting sun through a cloud.

Aah, well, we "light lab" people are completely happy when we manage it 
to create an absolute photo-realistic chrome sphere hovering above a 
checkered plane. Yes.


> We seem to be seeing opposite sides of the
> picture. One side assumes that by just reproducing how light is projected from
> objects onto the screen that that is enough, since past that point the eye is a
> mere recording device.

Says who? I would never say that. Seems more like you need this claim 
for your famous "two-fractions-theory".


> The other that that display is just a pattern of points
> of color that has to be perceived, re-seen, if you will, by the human eye to
> give it coherence, meaning, and going further. artistic expression.

Well, agreed, but I would also say that this point is of absolute no 
relevance within this discussion. This human "image-post-processing" and 
even this "giving it meaning" within my brain (or wherever) happens all 
the time anyway, everywhere. When I walk through the city, when I look 
outside the window when I'm in an art gallery and look at some painting 
or when I look at some CG image on my monitor.

I really do not think that there is anybody among us who thinks that 
human vision works like a camera lens and nothing more.

-Ive

Post a reply to this message

Am 02.12.2010 16:42, schrieb Stephen Klebs:
> "scott"<sco### [at] scottcom>  wrote:
>
>> Yes, it should be perfectly identical to if you'd set up the identical scene
>> in real life and taken a photo with a perfect camera.  This is the goal of
>> POV.
>
> Well, wake me up when you get there. I really want to see that. And even if you
> do get there, I'm not sure you will like what you see. I suggest you check a
> little article I read on how photographers like Ansel Adams had to use filers
> that I posted somewhere here.

That may well be, but a realistical simulation of the real world still 
allows you to place such fill lights, like a photographer would, for 
artistic purposes.

I guess in the long run POV-Ray may also end up supporting simulation of 
different photographic paper and such.


As an aside:

> There was similar quest years back about using computers to imitate visual
> perception, that is, computers that see. And in the end, with all the variables
> that couldn't be computed, like size constancy and object recognition and such,
> they gave up.

Ever read about RoboCup, a convention where robot builders from all the 
world come together to have their machines play soccer against one 
another? Or the US military's contest of computer-driven cars (whatever 
it was called)?

Forget about those people who gave up 10 years ago. Other people didn't, 
and are getting quite far by now.

Post a reply to this message

clipka <ano### [at] anonymousorg> wrote:
> As an aside:
>
> > There was similar quest years back about using computers to imitate visual
> > perception, that is, computers that see. And in the end, with all the variables
> > that couldn't be computed, like size constancy and object recognition and such,
> > they gave up.
>
> Ever read about RoboCup, a convention where robot builders from all the
> world come together to have their machines play soccer against one
> another? Or the US military's contest of computer-driven cars (whatever
> it was called)?
>
> Forget about those people who gave up 10 years ago. Other people didn't,
> and are getting quite far by now.

It would be infinitely cool if they did it but it also makes one appreciate how
amazing is the human brain. Even computers, the latest model of how it works,
can still not even come close.

Post a reply to this message

"Stephen Klebs" <skl### [at] gmailcom> wrote:
> I did not intend to raise such a hornet's nest here (maybe I did).
> But the debate is fascinated and it was great to see such life in the forum.

Yes indeed! Fascinating and informative. Your own arguments have been
well-thought-out and presented, and likewise the rebuttals.

In my experience, *whenever* the gamma issue has been raised, it's been a
hornet's nest!! ;-) Yet it's actually quite useful (IMO) to see the topic
discussed again like this, in depth. (I might even say it's the *state of the
art* on the subject.) I think this discussion has cleared up a lot of mystery,
among many of us here. In future, when I see a newsgroup poster asking about
gamma (yet again!), I think I'll refer him to your two posts. Much food for
thought, clearly presented.

CHEERS!
Ken

Post a reply to this message