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From: Pepi
Subject: One problem with photons
Date: 19 Sep 2003 18:30:01
Message: <web.3f6b82c01cbffe2d6e58dd1c0@news.povray.org>
I made scene with glass letters and three lights! I use photons to get
refraction of light:and all is ok, but letters give me shadows!
If I use shadoless in the light optins I also loose refraction of white
light in glass letters: so any advice will be very helpfull
Thanks


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From: Tim Nikias v2 0
Subject: Re: One problem with photons
Date: 19 Sep 2003 18:42:00
Message: <3f6b8638@news.povray.org>
That's proper functioning.
What photons do is simple: transparent
objects cast shadows like any other
solid object, and the actual light passing
through is calculated with photons. So,
unless you want to stick with realism,
you should place another lightsource
whereever the photons are coming from,
but apply a "projected_through" to it,
using the glass letters as object.

Example:
#declare Letters=union{ [3 Glass Letters] }
//Place Letters
object{Letters}
//Light-Position
#declare Light_Position=<50,50,-200>;
//Lightsource for refraction
light_source{ Light_Position rgb 1
 photons{reflection on refraction on}
}
//Lightsource for shadows
light_source{ Light_Position rgb 1
 photons{reflection off refraction off}
 projected_through{Letters}
}

The code above is untested, but should convey
the idea. I'm not sure if the photons-settings
for the shadow-light are functional like this, you
might have to look that up.

Regards,
Tim

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: no_lights (@) digitaltwilight.de

> I made scene with glass letters and three lights! I use photons to get
> refraction of light:and all is ok, but letters give me shadows!
> If I use shadoless in the light optins I also loose refraction of white
> light in glass letters: so any advice will be very helpfull
> Thanks
>


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From: Pepi
Subject: Re: One problem with photons
Date: 19 Sep 2003 19:25:01
Message: <web.3f6b8f858e0861336e58dd1c0@news.povray.org>
Hey thanks for quick answer! I made some birthday card and have letters for
name made in glass: you know how beatifull is dispersion in "diamond" like
objects made with photons and POV-Ray. So mine idea is to make "dimond
like" letters. Those letters will produce dispersion of white like : and
everything is good except shadow from letters (you are right in this piece
- I dont need realism/shadow for this part!
Now you are have clearer picture of mine problem!
Thanks one more time.
Pepi


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From: Tim Nikias v2 0
Subject: Re: One problem with photons
Date: 19 Sep 2003 19:36:37
Message: <3f6b9305$1@news.povray.org>
Well, then "projected_through" is the way to go.
Here's a small sample scene. The Glass-Sphere's
shadow is red, because it originates from the
red lightsource projecting through the sphere. I've
also made it less powerful. Note that the red light
will only cast through the sphere, so thats only where
the original shadow would be. Hence placing the
two lightsources at the same position: the first
casts a shadow, the second fills the shaded area
with light. It might be good to make the second
light a little weaker, so that at least a little shadow
is left.


global_settings{
 assumed_gamma 1
 photons{spacing .05 autostop .1}
 }
camera{location <0,2,-4> look_at <0,.5,0>}
#declare Glass_Ball=sphere{y,1
 pigment{rgbt <1,1,1,.99>}
 finish{
  specular .9 roughness .01
  reflection{0,.9 fresnel}
  }
 interior{ior 1.56}
 photons{refraction on target}
 }

object{Glass_Ball}
light_source{<20,30,40> rgb 1 photons{refraction on}}
light_source{<20,30,40> rgb x*.5 photons{refraction off reflection off}
projected_through{Glass_Ball}}
plane{y,0 pigment{rgb .5}}


Regards,
Tim

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: no_lights (@) digitaltwilight.de


> Hey thanks for quick answer! I made some birthday card and have letters
for
> name made in glass: you know how beatifull is dispersion in "diamond" like
> objects made with photons and POV-Ray. So mine idea is to make "dimond
> like" letters. Those letters will produce dispersion of white like : and
> everything is good except shadow from letters (you are right in this piece
> - I dont need realism/shadow for this part!
> Now you are have clearer picture of mine problem!
> Thanks one more time.
> Pepi
>


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From: Pepi
Subject: Re: One problem with photons
Date: 19 Sep 2003 20:15:01
Message: <web.3f6b9b9f8e086133d9bde8a90@news.povray.org>
Problem solved with projected throught option!
Your first example scene worked job in first place :)
Just now picture are in render process!
Really big thanks!
Pepi


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From: Warp
Subject: Re: One problem with photons
Date: 20 Sep 2003 06:29:28
Message: <3f6c2c08@news.povray.org>
Pepi <pal### [at] yahoocom> wrote:
> I made scene with glass letters and three lights! I use photons to get
> refraction of light:and all is ok, but letters give me shadows!

  Well, that is to be expected, isn't it? If light is refracted and
focused, it means that there are areas where less light will hit, thus
giving a shadow. That's only realistic with photons.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -


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