I've been trying too figure out if PovRay renders glass correctly or not.

If you have a glass sphere that is slightly green (like normal window
glass). With most ray tracers and renderers they just map a colour too the
surface of the glass resulting in an even distribution of transparent green
when rendered(like a balloon), with of course refraction added. In real life
the centre of the sphere is actually darker because the light travels a
longer distance through the middle of the sphere than near the edge.

If PovRay doesn't do this, I think it should be easy too make something to
do this: the longer the distance that the light travels through the object,
the more light is absorbed. But I know nothing about programming or
scripting(yet). I don't want to use it only in spheres but in other shapes
as well.

Is there someone that can help me with this?

Thanks

Nekar Xenos
_____________

'E xapis meta sou.

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On Tue, 9 Jan 2001 08:34:39 +0200, "J-Print News" <vir### [at] iconcoza>
wrote:

>I've been trying too figure out if PovRay renders glass correctly or not.

To an extent :)

>If you have a glass sphere that is slightly green (like normal window
>glass). With most ray tracers and renderers they just map a colour too the
>surface of the glass resulting in an even distribution of transparent green
>when rendered(like a balloon), with of course refraction added. In real life
>the centre of the sphere is actually darker because the light travels a
>longer distance through the middle of the sphere than near the edge.

In real life glass is green because it absorbs some blue and red. To
achieve the same effect, make your sphere clear white and add a
magenta absorbing media. It behaves in the exact same way as you are
asking. The surface does not need to have a color as it is infinitely
thin (in POV's way of thinking); think of it as coating. You can give
it a finish with reflection and specular highlights, of course.

>If PovRay doesn't do this, I think it should be easy too make something to
>do this: the longer the distance that the light travels through the object,
>the more light is absorbed. 

This is exactly what absorbing media does. 

You can also use light attenuation which is faster. In official POV it
is not very accurate, I think, but MegaPOV offers an alternative
formula which is real-life based.

Note: I may be thining of light fading here but I don't have Mega
installed yet to check out (did a full reinstall just yesterday).


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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Thanks

Is MegaPov free? Where can I get it?

Nekar
Peter Popov <pet### [at] vipbg> wrote in message
news:c7el5tc1ci9jj2lg2mtj4gsn4qk3q81o6c@4ax.com...
> On Tue, 9 Jan 2001 08:34:39 +0200, "J-Print News" <vir### [at] iconcoza>
> wrote:
>
> >I've been trying too figure out if PovRay renders glass correctly or not.
>
> To an extent :)
>
> >If you have a glass sphere that is slightly green (like normal window
> >glass). With most ray tracers and renderers they just map a colour too
the
> >surface of the glass resulting in an even distribution of transparent
green
> >when rendered(like a balloon), with of course refraction added. In real
life
> >the centre of the sphere is actually darker because the light travels a
> >longer distance through the middle of the sphere than near the edge.
>
> In real life glass is green because it absorbs some blue and red. To
> achieve the same effect, make your sphere clear white and add
> it a finish with reflection and specular highlights, of course.
>
> >If PovRay doesn't do this, I think it should be easy too make something
to
> >do this: the longer the distance that the light travels through the
object,
> >the more light is absorbed.
>
> This is exactly what absorbing media does.
>
> You can also use light attenuation which is faster. In official POV it
> is not very accurate, I think, but MegaPOV offers an alternative
> formula which is real-life based.
>
> Note: I may be thining of light fading here but I don't have Mega
> installed yet to check out (did a full reinstall just yesterday).
>
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] vipbg
> TAG      e-mail : pet### [at] tagpovrayorg

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J-Print News wrote:
> Is MegaPov free? Where can I get it?

Yes, and right here:
http://nathan.kopp.com/patched.htm

--
Lance.

http://come.to/the.zone

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In article <c7el5tc1ci9jj2lg2mtj4gsn4qk3q81o6c@4ax.com>, Peter Popov 
<pet### [at] vipbg> wrote:

> Note: I may be thining of light fading here but I don't have Mega
> installed yet to check out (did a full reinstall just yesterday).

It sounds like you mean the fade_color addition...it lets you specify 
the color that light passing through the object attenuates to, and adds 
an attenuation calculation that is supposed to be more realistic. And it 
has nothing to do with light source fading, it is more of a solid-color 
media-like effect.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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J-Print News wrote:

> I've been trying too figure out if PovRay renders glass correctly or not.

Yes and no. That answer your question? ;)
(looks like Peter's explained it already)

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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interior
{ fade_distance ...
  fade_power ...
}

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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In article <3a5c3edb@news.povray.org>, Warp <war### [at] tagpovrayorg> 
wrote:

> interior
> { fade_distance ...
>   fade_power ...
> }

And don't forget the fade_color available in MegaPOV.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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I just thought of something else. Glass reflects not only on the outside but
on the inside as well. If you look carefully at a window pane at night
you'll notice there is actually a double reflection.

Can this be done in Pov?

Thanks

Nekar

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On Tue, 09 Jan 2001 12:09:44 -0500, Chris Huff <chr### [at] maccom>
wrote:

>It sounds like you mean the fade_color addition...it lets you specify 
>the color that light passing through the object attenuates to, and adds 
>an attenuation calculation that is supposed to be more realistic. And it 
>has nothing to do with light source fading, it is more of a solid-color 
>media-like effect.

I actually mean this:

>:: 7.2. Realistic attenuation
>:: If you set fade_power in the interior of an object at 1000 or above, 
>:: MegaPov will use a realistic exponential attenuation function:
>:: 
>:: Attenuation = exp(-depth/fade_dist)
>:: 
>:: Colored attenuation does work with this exponential attenuation also.

Sorry abouit not being precise before but I just finished installing.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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