Stephen <mcavoys_at@aoldotcom> wrote:
> Can anyone suggest how to create a Crescent Moon where the unlit part is
> not visible?

I've done this before. Put your moon and light source outside a semitransparent,
hollow, no_shadow sky sphere, with a black background. If using radiosity, make
sure the outer texture of the sphere is set to opaque black (unless you want the
shadowed side of the moon to be brightly earthlit!)

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Stephen wrote:

> Can anyone suggest how to create a Crescent Moon where the unlit part is 
> not visible?

Use no_radiosity and ambient 0 for the moon,
and fade_power 2 as well as a reasonable fade_distance
for all non-Sun light_sources. You probably want to
ignore Earthshine, otherwwise you require photons
(for crescent moon "Earthshine" is dominated by
light refracted in the atmosphere). During full
moon it's more reflected light (radiosity?) but you
could only notice it during a lunar eclipse anyway.

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> Can anyone suggest how to create a Crescent Moon where the unlit part is
> not visible?
>

Make your "sky" transparent.
Make sure to set ambient 0 for your moon.
Make sure that your moon is farther away than your sky.



Alain

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On Tue, 11 Jan 2011 17:21:09 +0200, Stephen <mcavoys_at@aoldotcom> wrote:

> Can anyone suggest how to create a Crescent Moon where the unlit part is  
> not visible?
>

I think simulation would be the most realistic way. Have a planet with  
atmosphere and an iso-surface moon and a sun.

You can play around with mediasky.pov from the sample scenes under  
advanced. Or you can download nx_planets from the object collection to  
make a planet with atmosphere.

You can also play around with
http://news.povray.org/povray.text.scene-files/thread/%3Cop.u61y64hyufxv4h%40xena%3E/

-- 
-Nekar Xenos-

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"Bill Pragnell" <bil### [at] hotmailcom> schreef in bericht 
news:web.4d2c7d03db8fc2836dd25f0b0@news.povray.org...
> I've done this before. Put your moon and light source outside a 
> semitransparent,
> hollow, no_shadow sky sphere, with a black background. If using radiosity, 
> make
> sure the outer texture of the sphere is set to opaque black (unless you 
> want the
> shadowed side of the moon to be brightly earthlit!)

...and that works perfectly!

I put a little example code in povray.text.scene-files

Thomas

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On 12/01/2011 8:13 AM, Thomas de Groot wrote:
> "Bill Pragnell"<bil### [at] hotmailcom>  schreef in bericht
> news:web.4d2c7d03db8fc2836dd25f0b0@news.povray.org...
>> I've done this before. Put your moon and light source outside a
>> semitransparent,
>> hollow, no_shadow sky sphere, with a black background. If using radiosity,
>> make
>> sure the outer texture of the sphere is set to opaque black (unless you
>> want the
>> shadowed side of the moon to be brightly earthlit!)
>
> ....and that works perfectly!
>
> I put a little example code in povray.text.scene-files
>

Thanks Thomas.
The only problem with this method is that the Moon is coloured by the 
Sphere of the Sky (we need a name for this as skysphere is something 
else). In your example the sky is too light, in my opinion. But it 

example, looked washed out.
For a darker blue sky I got slightly better results by using a small 
fade distance and a large colour value but I suspect that I would need 



is fine for a gibbous Moon. But when the Moon is a crescent you can see 

part away to get the best result.
It is a work-around but all art is artifice.
Thanks to all.


-- 
Regards
     Stephen

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"Stephen" <mcavoys_at@aoldotcom> schreef in bericht 
news:4d2dbd9a$1@news.povray.org...
> Thanks Thomas.
> The only problem with this method is that the Moon is coloured by the 
> Sphere of the Sky (we need a name for this as skysphere is something 
> else).

That is what happens also in RL...

Thomas

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On 12/01/2011 3:51 PM, Thomas de Groot wrote:
> "Stephen"<mcavoys_at@aoldotcom>  schreef in bericht
> news:4d2dbd9a$1@news.povray.org...
>> Thanks Thomas.
>> The only problem with this method is that the Moon is coloured by the
>> Sphere of the Sky (we need a name for this as skysphere is something
>> else).
>
> That is what happens also in RL...
>

notice it.
Must be a Gamma problem :-P


-- 
Regards
     Stephen

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Stephen <mcavoys_at@aoldotcom> wrote:
> On 12/01/2011 3:51 PM, Thomas de Groot wrote:
> > "Stephen"<mcavoys_at@aoldotcom>  schreef in bericht
> > news:4d2dbd9a$1@news.povray.org...
> >> Thanks Thomas.
> >> The only problem with this method is that the Moon is coloured by the
> >> Sphere of the Sky (we need a name for this as skysphere is something
> >> else).
> >
> > That is what happens also in RL...
> >

> notice it.
> Must be a Gamma problem :-P

Hmm, I notice it every time I see the moon in daylight... the lunar seas appear
more sky-coloured than the brighter areas, as do crater shadows if looking
through a telescope.

Or do you mean that even the brightly-lit areas are sky-coloured? You might need
to crank up your moon's diffuse value to ensure a decent white colour if that's
the case.

Bill

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On 12/01/2011 4:29 PM, Bill Pragnell wrote:
> Hmm, I notice it every time I see the moon in daylight... the lunar seas appear
> more sky-coloured than the brighter areas, as do crater shadows if looking
> through a telescope.
>

Right! The next clear day when the moon is out, I'll have a proper look. :-)

> Or do you mean that even the brightly-lit areas are sky-coloured? You might need
> to crank up your moon's diffuse value to ensure a decent white colour if that's
> the case.
>

That is it :-D
Diffuse and brilliance settings.

Thanks.

-- 
Regards
     Stephen

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