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I thought a nice experiment would be to create a telescope to apply to the
Niagara images. When I did, the reults were surprising. I do not understand
Media enough to know why the media cirrus clods change the light in the
lense. Can anybody help? The only thing changed between renderings is the
cirrus clouds.
Here is the lens code:
#declare R = .00007 ;
#declare Lens =
union{
intersection{
sphere{<0,0,0>, R translate<0,0,-R/1.0071>}
sphere{<0,0,0>, R translate<0,0,R/1.0071>}
cylinder{<0,0,.005>,<0,0,-.005>,0.00002}
texture{pigment{rgbt<1,1,1,1>} }
interior{
ior 1.52
}
}
difference{
cylinder{<0,0,.0000005>,<0,0,-.0000005>,0.0000083}
cylinder{<0,0,.0000006>,<0,0,-.0000006>,0.00000785}
texture{T_Brass_3B}
}
}
Here is the cirrus cloud code straight out of Jamies Tierra inc file.
/*
Persistence of Vision Ray Tracer Scene Description File
Tierra v1.0 - Cirrus shell include
--
Jaime Vives Piqueres, Apr-May-Jun 2004.
*/
#if (use_cirrus)
// basic cloud pigment maped spherically
#declare d_base=
density{
Cirrus_Density
color_map{
[0.00 rgb 0]
[(1-Cirrus_Level) rgb 0]
[(1-Cirrus_Level)+Cirrus_Border rgb 1]
[1.00 rgb 1]
}
warp{spherical}
// changing default orientation to match scene orientation
rotate 90*x
rotate 360*rand(r_clouds)*z
}
// density with a tiny layer of clouds
#declare d_clouds=
density{
spherical
density_map{
[0.0 d_base]
[Cirrus_Flatness d_base]
[Cirrus_Flatness rgb 0]
[1.0 rgb 0]
}
}
// shell sphere with media cirrus
difference{
sphere{0,1}
sphere{0,1-Cirrus_Flatness}
hollow
texture{pigment{rgbt 1}}
interior{
media{
intervals Clouds_Intervals
absorption .04*5
scattering{1,.04}
density{d_clouds}
}
}
// scale somewhat like earth in km
scale 6800
translate (-6800+Cirrus_Height)*y
}
#end
Thanks for your help,
Tim
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Attachments:
Download 'without-clouds.jpg' (125 KB)
Preview of image 'without-clouds.jpg'
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Your lens is very thin. After a ray hits a transparent surface, I believe it
travels a slight distance ahead before it resumes testing for surfaces, to
avoid reintersecting the same surface. It's possible that this little jump
is longer than the depth of the lens, causing the ray to think it's still
inside the lens. This could mess up media. I also notice that your sky looks
different within the lens even in the first image. I'm not sure why this
would cause the lens in the second image to appear *darker*, but this may be
to blame in some non-obvious way. (This problem, if it is a problem, would
also cause your lens refractions to be incorrect.)
Try making your lens much larger and just moving it farther away to
compensate.
- Slime
[ http://www.slimeland.com/ ]
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