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  rendering glass (Message 1 to 3 of 3)  
From: syngola
Subject: rendering glass
Date: 12 Sep 2008 12:35:00
Message: <web.48ca99aedffcddb159f4be7e0@news.povray.org>
Hi everyone,

i played a little with cutting nested spheres with another one. would like to
know what to improve on the texture. i am quite unsure if the lower region of
the outer sphere isn't too bright.

regards, peter


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From: Alain
Subject: Re: rendering glass
Date: 12 Sep 2008 22:49:09
Message: <48cb2a25@news.povray.org>
syngola nous illumina en ce 2008-09-12 12:32 -->
> Hi everyone,
> 
> i played a little with cutting nested spheres with another one. would like to
> know what to improve on the texture. i am quite unsure if the lower region of
> the outer sphere isn't too bright.
> 
> regards, peter
> 
> 
> ------------------------------------------------------------------------
> 
Nice.
You should note that the hot spot under your hollow nested spheres should NOT be 
there. They are effectively acting as divergent lences. Apparently, you used the 
caustics keyword, remove it and use photons to get a realistic effect.
Set your spheres in an union, and give it the following:
photons{target refraction on reflection on}

and add the followint to your global_settings:
photons{spacing 0.1}//minimal basic photons block

About the finish:
How much ambient do you have? It looks like it's set to high. It may be better 
with ambient 0, a low difuse, like difuse 0.5 or maybe less. Usualy, glass rely 
on it's interior more than on it's surface for it's colouration and aspect.

Glass, and almost every transparent substances have variable reflection. Low 
value (about 0.1 for glass) when viewed perpendicaly, almost 1 for tangent rays. 
Also set fresnel on.
Don't forget to set conserve_energy in your finish.
The pigment can be close to rgbt 1.
For the interior:
Rely more on fade_color, fade_distance and fade_power to get your colouration. 
In your case, you'll need a small fade_distance, about 1/2 the thickness of your 
shell. Reduce that value for the inner shells, as well as making the fade_color 
darker.
Realistic value for the fade_power of tranparent substances are 1 or 1001.
It look like your glass contains some media. If it does, and it's emissive 
media, change it to scatthering media. Your glass is not supposed to emit light.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when your wife's raytraced image you 
made to flatter her is the only one you see of her anymore.
Ken Tyler


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From: syngola
Subject: Re: rendering glass
Date: 14 Sep 2008 14:00:00
Message: <web.48cd4ff6e70960fe579c94120@news.povray.org>
Hi,

thank you for your really detailed answer. most of the things you mentioned
where already in my code, but you couldn't know of course.

I tried several things, but i must say that controlling the color with fade
color is extraordinarily difficult for me and i didn't get any reasonable
results. also fresnel reflection doesn't give me the feel i wanted although it
might be more in realistic in the physical manner.

i removed the caustics statement from the interior too, and now this dumb spot
has also vanished ;)

again thank you for your efforts :)

regards, peter


Alain <ele### [at] netscapenet> wrote:
> syngola nous illumina en ce 2008-09-12 12:32 -->
> > Hi everyone,
> >
> > i played a little with cutting nested spheres with another one. would like to
> > know what to improve on the texture. i am quite unsure if the lower region of
> > the outer sphere isn't too bright.
> >
> > regards, peter
> >
> >
> > ------------------------------------------------------------------------
> >
> Nice.
> You should note that the hot spot under your hollow nested spheres should NOT be
> there. They are effectively acting as divergent lences. Apparently, you used the
> caustics keyword, remove it and use photons to get a realistic effect.
> Set your spheres in an union, and give it the following:
> photons{target refraction on reflection on}
>
> and add the followint to your global_settings:
> photons{spacing 0.1}//minimal basic photons block
>
> About the finish:
> How much ambient do you have? It looks like it's set to high. It may be better
> with ambient 0, a low difuse, like difuse 0.5 or maybe less. Usualy, glass rely
> on it's interior more than on it's surface for it's colouration and aspect.
>
> Glass, and almost every transparent substances have variable reflection. Low
> value (about 0.1 for glass) when viewed perpendicaly, almost 1 for tangent rays.
> Also set fresnel on.
> Don't forget to set conserve_energy in your finish.
> The pigment can be close to rgbt 1.
> For the interior:
> Rely more on fade_color, fade_distance and fade_power to get your colouration.
> In your case, you'll need a small fade_distance, about 1/2 the thickness of your
> shell. Reduce that value for the inner shells, as well as making the fade_color
> darker.
> Realistic value for the fade_power of tranparent substances are 1 or 1001.
> It look like your glass contains some media. If it does, and it's emissive
> media, change it to scatthering media. Your glass is not supposed to emit light.
>
> --
> Alain
> -------------------------------------------------
> You know you've been raytracing too long when your wife's raytraced image you
> made to flatter her is the only one you see of her anymore.
> Ken Tyler


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