I want to create something like picture on the entrance page of
www.planetside.co.uk
I want to create a moon (or two moons, or giant planet, whatever) over the
landscape, behind the clouds. This is effect that you can see if the moon is
visible during the daylight. You can see white halfmoon, with craters and
stuff, and the other half in the color of sky.
Is it possible without cheating (I mean no discs, Boolean objects and stuff
like this)? I am aware that this effect is result of atmosphere's
influence on light (the reason why the sky is blue). Can it be simulated in
POV?

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On Tue, 2 Nov 1999 08:55:47 +0100, "Trole" <tro### [at] pttyu> wrote:

>I want to create something like picture on the entrance page of
>www.planetside.co.uk
>I want to create a moon (or two moons, or giant planet, whatever) over the
>landscape, behind the clouds. This is effect that you can see if the moon is
>visible during the daylight. You can see white halfmoon, with craters and
>stuff, and the other half in the color of sky.
>Is it possible without cheating (I mean no discs, Boolean objects and stuff
>like this)? I am aware that this effect is result of atmosphere's
>influence on light (the reason why the sky is blue). Can it be simulated in
>POV?

Make the moon the color of the sky, give it a high ambient and make
the craters with a bump map. This way you won't see any bumps in the
shadow but you'll see the craters in the lit area. Hope this works



Peter Popov
ICQ: 15002700

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> I want to create something like picture on the entrance page of
> www.planetside.co.uk
> I want to create a moon (or two moons, or giant planet, whatever) over the
> landscape, behind the clouds. This is effect that you can see if the moon
is
> visible during the daylight. You can see white halfmoon, with craters and
> stuff, and the other half in the color of sky.
> Is it possible without cheating (I mean no discs, Boolean objects and
> stuff like this)? I am aware that this effect is result of atmosphere's
> influence on light (the reason why the sky is blue). Can it be simulated
> in POV?

Here's an untested idea you can try. Keeping your background to the default
black, create your moon(s)/planet(s) as you normally would, with ambient 0,
so the unlit parts look black. Now create a large sphere and make it
semi-transparent. Make it's large enough that it doesn't get in the way of
anything you have in your sky, but also make sure the moon(s)/planet(s) are
outside the sphere. This sphere will act as your atmosphere and shade
everything to whatever colour you give your it.

Hope that helps,
Darcy

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>Make the moon the color of the sky, give it a high ambient and make
>the craters with a bump map. This way you won't see any bumps in the
>shadow but you'll see the craters in the lit area. Hope this works

>
>
>Peter Popov
>ICQ: 15002700

It works. Thank you, Peter. Only problem is that I can not use gradient
colors for sky, but, you can't get everything. A layers of fogs and clouds
will fix it...

Trole

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Hello Trole. I have a method that works well for me. The concept is to make the
moon white, but give it an ambient that is the same as the background color.
With a texture_map you can have a variance in the pigment's surface value. Here
is some code:

light_source{<100000,200000,0>,<1,1,.8>}

background{rgb<.3 .5 1>}

sphere{<0,20000,100000>,20000
 texture{bumps scale 3000 turbulence .75
  texture_map{
   [0 pigment{rgb 1}finish{diffuse .3 ambient<.3 .5 1>}]
   [1 pigment{rgb 1}finish{diffuse .5 ambient<.3 .5 1>}]
  }
 }
}

Trole wrote:

> I want to create something like picture on the entrance page of
> www.planetside.co.uk
> I want to create a moon (or two moons, or giant planet, whatever) over the
> landscape, behind the clouds. This is effect that you can see if the moon is
> visible during the daylight. You can see white halfmoon, with craters and
> stuff, and the other half in the color of sky.
> Is it possible without cheating (I mean no discs, Boolean objects and stuff
> like this)? I am aware that this effect is result of atmosphere's
> influence on light (the reason why the sky is blue). Can it be simulated in
> POV?

--
Samuel Benge

STB### [at] aolcom

"And you can fly
 High as a kite if you want to
 Faster than light if you want to
 Speeding through the universe
 Thinking is the best way to travel"

          -The Best Way to Travel, The Moody Blues

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On Thu, 4 Nov 1999 01:06:34 +0100, "Branimir Troshic" <tro### [at] pttyu>
wrote:

>It works. Thank you, Peter. Only problem is that I can not use gradient
>colors for sky, but, you can't get everything. A layers of fogs and clouds
>will fix it...
>
>Trole

Lo and behold, it worked :) I am no less surprised than you are


Here goes another shot in the dark (or more like daylight :) ). OK, so
your gradient sky problem is that the moon's plain color shows. Two
approaches come to mind:

1. Put the moon in a part of the sky where the latter's colour is
constant. And yeah, that's chickening out.

2. This one requires some heavy math. You'll need to know how the
gradient of the sky will look when perspective-mapped on the Moon with
respect to the viewpoint. Let me clarify a bit more on this:
  a) calclulate a ray from the camera to the lower edge of the moon
and see where it will intersect the sky. Of course, you will need to
use a sky sphere instead of a sky_sphere to do that :) Then use the y
coordinate of the intersection point to calculate the position in the
color_map and hence the color of the point in question
  b) do the same for the upper edge of the moon
  c) replace the solid color of the moon with a gradient

You can use the trace funtion of the SuperPatch or plain POV (but the
math is not easy). I think someone made an "evaluate pigment" patch
which could also be handy but again, it can be done with more trig
etc.

3. Another idea that just came to me is that you can give the Moon a
gradient pigment_map with a somewhat sharp transition from clear to
its normal color/image map, with the gradient vector pointing at the
Sun. Beware, though! The gradient pattern 'flips' at the origin, i.e.
changes direction.

I realise this post is somewhat late but I just found it in my outbox,
half-written and saved. And I opened the outbox by chance. Anyway, I
hope it helps in your endeavors.


Peter Popov
ICQ: 15002700

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