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From: Simon Adameit
Subject: pigment clouds
Date: 28 Jul 2002 20:24:53
Message: <3d448b55@news.povray.org>
Hi all,

I tried to do some clouds using only one sphere with a texture.
What do you think? Any ideas what I could improve?
If not than I'm going to try to animate them.


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From: Sir Charles W  Shults III
Subject: Re: pigment clouds
Date: 28 Jul 2002 20:27:46
Message: <3d448c02@news.povray.org>
It is a nice effect, but they do not recede properly with distance.  They
appear to be pasted on a wall and cut off with an index card.
    If they became much smaller toward your horizon, they would look pretty
good.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip


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From: Simon Adameit
Subject: Re: pigment clouds
Date: 28 Jul 2002 20:36:02
Message: <3d448df2@news.povray.org>
"Sir Charles W. Shults III" <aic### [at] cflrrcom> schrieb im Newsbeitrag
news:3d448c02@news.povray.org...
>     It is a nice effect, but they do not recede properly with distance.
They
> appear to be pasted on a wall and cut off with an index card.
>     If they became much smaller toward your horizon, they would look
pretty
> good.
>

The problem is that they need to be on a sphere for the shading to work
correct.
But I'll see if I can somehow fake perspective by transforming the texture.

Simon


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From: Peter Popov
Subject: Re: pigment clouds
Date: 29 Jul 2002 03:55:35
Message: <56t9kuo8mtfmnsqlhi5evfnmli0i12hct7@4ax.com>
On Mon, 29 Jul 2002 02:32:43 +0200, "Simon Adameit" <gom### [at] gmxde>
wrote:

>The problem is that they need to be on a sphere for the shading to work
>correct.
>But I'll see if I can somehow fake perspective by transforming the texture.

Maybe a black_hole warp with linear falloff placed in the vanishing
point? Just an idea, of course it might just look ugly.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg


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From: Slime
Subject: Re: pigment clouds
Date: 29 Jul 2002 05:10:24
Message: <3d450680@news.povray.org>
> I tried to do some clouds using only one sphere with a texture.
> What do you think? Any ideas what I could improve?
> If not than I'm going to try to animate them.

1. if you want a sky formed by a pigment on a sphere, look up the sky_sphere
keyword.

2. Use a plane, not a sphere,  so that the perspective is right near the
horizon.

 - Slime
[ http://www.slimeland.com/ ]


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From: Simon Adameit
Subject: Re: pigment clouds
Date: 29 Jul 2002 06:23:46
Message: <3d4517b2$1@news.povray.org>
"Slime" wrote:
> 1. if you want a sky formed by a pigment on a sphere, look up the
sky_sphere
> keyword.

I already know about sky_sphere but it would'nt be of any use in this case
because I need a texture wich is illuminated by the sun and not a pigment.

> 2. Use a plane, not a sphere,  so that the perspective is right near the
> horizon.
>

To get the perspective right I would have to use a sphere translated into
the bottom to make the clouds disappear behind the horizon like they do in
the real world. But neither this nor a plane would work in this case because
the sphere is needed to simulate the shading of the clouds.

Simon


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From: Simon Adameit
Subject: Re: pigment clouds
Date: 29 Jul 2002 06:30:04
Message: <3d45192c@news.povray.org>
"Peter Popov" wrote:
>
> Maybe a black_hole warp with linear falloff placed in the vanishing
> point? Just an idea, of course it might just look ugly.
>

Thanks. But I already found a solution using functions.


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From: Bill DeWitt
Subject: Re: pigment clouds
Date: 29 Jul 2002 08:22:42
Message: <3d453392$1@news.povray.org>
"Simon Adameit" <gom### [at] gmxde> wrote in message
news:3d448b55@news.povray.org...
> Hi all,
>
> I tried to do some clouds using only one sphere with a texture.
> What do you think? Any ideas what I could improve?
> If not than I'm going to try to animate them.

    Well, I kinda like them how they are. I see the problems you mention,
but I was watching some clouds the other day and I have come to the
conclusion that many natural cloud formations, if represented accurately in
povray, would not seem natural. One from the beach the other day was nothing
but a greenish grey line across the horizon with three bulbous areas with
rainbow colors. If I had taken a picture of it and edited it to make it look
like povray, no one here would have even thought I was posting clouds, it
looked more like a fractal.

    So from my point of view, your clouds look like clouds. They look a lot
like oil painted clouds.


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From: Samuel Benge
Subject: Re: pigment clouds
Date: 29 Jul 2002 14:13:03
Message: <3D4585A9.8070708@caltel.com>
Hello Simon. As mentioned by others, you may need to dimish the scale of 
the clouds as they recede into the distance. One way I've found to do 
this is by using functions. Here is a little piece of code that uses a 
sky_sphere (POV version 3.5):

#declare Pgm=function{pigment{granite}}
#declare Scale=2;
sky_sphere{
  pigment{
   function{Pgm(x/y/Scale,y/y/Scale,z/y/Scale).grey}
  }
}

It shouldn't be too hard to make this code work with your more complex 
pigment (texture?). This method can be used for a number of 
fast-rendering background effects. If you use this method, you might 
also want to use fog, as the pigment gets really jumbled near the horizon.

Simon Adameit wrote:

> Hi all,
> 
> I tried to do some clouds using only one sphere with a texture.
> What do you think? Any ideas what I could improve?
> If not than I'm going to try to animate them.
> 
> 
> 
> 
> 


-- 
Samuel Benge

sbe### [at] caltelcom


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From: Simon Adameit
Subject: Re: pigment clouds
Date: 29 Jul 2002 14:42:27
Message: <3d458c93@news.povray.org>
"Samuel Benge" wrote:
>  If you use this method, you might
> also want to use fog, as the pigment gets really jumbled near the horizon.
>
Thanks for your solution, but I already found it myself.
If you don't want the clouds to get infinity small at the horizon use
something like this:
function{Pgm(x/(y/Scale+.1),...

Simon


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