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Blue Herring wrote:
> Really great! If you hadn't told me, I would have thought it was real.
Hey, thanks!
Sam
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"stbenge" <stb### [at] hotmail com> schreef in bericht
news:48599751$1@news.povray.org...
>
> Nebulae are one of the most visually striking celestial bodies out there.
> Just imagine living on a planet close to one! Of course, you'd probably be
> bombarded with intense radiation. Extrasolar organisms (if they exist)
> living under those conditions probably have a high tolerance to excessive
> radiation, though.
>
One thing I wonder at: Most photographs of nebulae we are shown by NASA, are
in false colour? So, what is the real aspect? I suppose just a cloud of
fairly monochromatic light?
Thomas
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"Thomas de Groot" <t.d### [at] inter nlDOTnet> wrote:
> "stbenge" <stb### [at] hotmail com> schreef in bericht
> news:48599751$1@news.povray.org...
> >
> > Nebulae are one of the most visually striking celestial bodies out there.
> > Just imagine living on a planet close to one! Of course, you'd probably be
> > bombarded with intense radiation. Extrasolar organisms (if they exist)
> > living under those conditions probably have a high tolerance to excessive
> > radiation, though.
> >
>
> One thing I wonder at: Most photographs of nebulae we are shown by NASA, are
> in false colour? So, what is the real aspect? I suppose just a cloud of
> fairly monochromatic light?
>
> Thomas
Not much to see in the visible spectrum
Detail in the visible wavelength is not as good as others so they take pictures
in the other wavelengths. The new detail gets a color, which could only be
"false" by default.
Your EMS:
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
aQ
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Attachments:
Download 'emsurface.jpg' (95 KB)
Preview of image 'emsurface.jpg'
![emsurface.jpg](/povray.binaries.images/attachment/%3Cweb.485a8f9e9ed14b541e1c79870%40news.povray.org%3E/emsurface.jpg?preview=1)
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stbenge wrote:
> Considering the amount of light attenuation in a nebula, I'd have to say
> that they are even less dense than our own atmosphere on Earth.
Hah, that's a good one - it's called high-density nebulae
when it has about 10,000 atoms per cubic centimeter, which
is also called ultra high quality vacuum in earth labs ;)
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Christian Froeschlin wrote:
> stbenge wrote:
>
>> Considering the amount of light attenuation in a nebula, I'd have to
>> say that they are even less dense than our own atmosphere on Earth.
>
> Hah, that's a good one - it's called high-density nebulae
> when it has about 10,000 atoms per cubic centimeter, which
> is also called ultra high quality vacuum in earth labs ;)
Lol, I guess it's much worse than I imagined!
Sam
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Thomas de Groot wrote:
> "stbenge" <stb### [at] hotmail com> schreef in bericht
> news:48599751$1@news.povray.org...
>> Nebulae are one of the most visually striking celestial bodies out there.
>> Just imagine living on a planet close to one! Of course, you'd probably be
>> bombarded with intense radiation. Extrasolar organisms (if they exist)
>> living under those conditions probably have a high tolerance to excessive
>> radiation, though.
>
> One thing I wonder at: Most photographs of nebulae we are shown by NASA, are
> in false colour? So, what is the real aspect? I suppose just a cloud of
> fairly monochromatic light?
>
> Thomas
Surely there must be *something* to see, even it is a bit of silver lining.
Sam
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alphaQuad wrote:
> "Thomas de Groot" <t.d### [at] inter nlDOTnet> wrote:
>> One thing I wonder at: Most photographs of nebulae we are shown by NASA, are
>> in false colour? So, what is the real aspect? I suppose just a cloud of
>> fairly monochromatic light?
>>
>> Thomas
>
> Not much to see in the visible spectrum
>
> Detail in the visible wavelength is not as good as others so they take pictures
> in the other wavelengths. The new detail gets a color, which could only be
> "false" by default.
Yeah, the visible spectrum is a sliver compared to everything else.
Nebulae *are* lit by stars, aren't they? Surely there must be something
to see, using *really* sensitive film. Night vision probably wouldn't
capture the real colors, so some other method would have to be used.
Sam
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stbenge napsal(a):
> Christian Froeschlin wrote:
>> stbenge wrote:
>>
>>> Considering the amount of light attenuation in a nebula, I'd have to
>>> say that they are even less dense than our own atmosphere on Earth.
>>
>> Hah, that's a good one - it's called high-density nebulae
>> when it has about 10,000 atoms per cubic centimeter, which
>> is also called ultra high quality vacuum in earth labs ;)
>
> Lol, I guess it's much worse than I imagined!
>
> Sam
they are also ultra-huge :-)
--
You know you've been raytracing too long when...
you ever saw a beautiful scenery and regretted not to take your 6"
reflective ball and a digital camera, thinking "this would have been a
perfect light probe"
-Johnny D
Johnny D
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Roman Reiner wrote:
> Oops, my bad! Actually i wanted to know how you created the nebula itself. That
> would be step 2 then?
>
> I'm asking because i have some experience with making nebulas in Photoshop and i
> have no problems doing starfields, grain and bloom, but the nebulas itself
> although handpainted never looked as good as in your image. Assuming that you
> made the nebula with produrals too this is quite impressive.
>
> I hope you can give me some info on this, and sorry again for asking for the
> wrong thing ;)
>
> Regards Roman
Hi Roman,
Here is the code for the nebula and a few stars. This was rendered over
an image of a star field, the code for which I have left out. Making a
star field yourself isn't too hard (though it requires some tweaking to
look right), and you can place the resulting image behind the nebula
scene with Rune's illusion.inc file. The density pattern is kept simple
to reduce render times. Adding turbulence and/or density maps to it can
make the render times skyrocket. Also, notice how I kept the whole scene
very small, unit-wise. Media at larger sizes tends to have strange
artifacts for some reason.
#declare R=seed(005);
camera{
right x*4/3 up y*1
location<0,0,-20>
look_at 0
angle 10
}
// a macro star object
#macro bright_star(bsrgb)
disc{0,z,1
pigment{
pigment_pattern{
cylindrical rotate x*90
poly_wave 32
}
pigment_map{
[0 rgb 0 transmit 1]
[1 rgb bsrgb*2]
}
scale 2
}
finish{ambient 1 diffuse 0}
scale .03
hollow
}
#end
// a few stars placed behind and in front of the nebula
#declare V=0;
#while(V<100)
object{
bright_star(<rand(R),rand(R),rand(R)>+1) scale .2+rand(R)*5
translate<-4+rand(R)*8,-2+rand(R)*4,1.01+rand(R)*2>
}
#if(rand(R)>.75)
object{
bright_star(<rand(R),rand(R),rand(R)>+1) scale .2+rand(R)*5
translate<-4+rand(R)*8,-2+rand(R)*4,-1.01-rand(R)*2>
}
#end
#declare V=V+1;
#end
// a light illuminating the nebula
light_source{<2,2.8,0>,10 fade_power 2 fade_distance 1}
// the nebula
box{
<-3,-2,-1>,<3,2,1>
pigment{rgbt 1}
interior{
media{
// the overall media density
#declare thick=40;
scattering{5,<1,.7,.3>*thick}
absorption thick-<1,.7,.3>*thick/4
// change intervals to 1 for testing purposes
intervals 5
density{
granite
poly_wave 1.5
translate z*23
scale 8
color_map{
[0 rgb 1]
[.05 rgb .025]
[.125 rgb .0025]
[.5 rgb 0]
}
}
}
}
hollow
}
Sam
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"stbenge" <stb### [at] hotmail com> schreef in bericht
news:485ad90c@news.povray.org...
> alphaQuad wrote:
>>
>> Not much to see in the visible spectrum
>>
>> Detail in the visible wavelength is not as good as others so they take
>> pictures
>> in the other wavelengths. The new detail gets a color, which could only
>> be
>> "false" by default.
>
> Yeah, the visible spectrum is a sliver compared to everything else.
> Nebulae *are* lit by stars, aren't they? Surely there must be something to
> see, using *really* sensitive film. Night vision probably wouldn't capture
> the real colors, so some other method would have to be used.
>
Indeed.
My point is that we are so used to see the false colour pictures that we
*think* that is really how we would see the nebulae, from a spaceship for
instance... Oh well, just nitpicking :-) Those false colour images are
gorgeous anyway! ...and they are real too!
Thomas
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