POV-Ray : Newsgroups : povray.advanced-users : Looking for ideas Server Time
30 Jul 2024 02:22:50 EDT (-0400)
  Looking for ideas (Message 1 to 4 of 4)  
From: Geoff Wedig
Subject: Looking for ideas
Date: 1 Sep 2000 08:38:34
Message: <39afa34a@news.povray.org>
I've got a project that requires a couple of things that I haven't figured
out a good way to do yet, so I figured I'd ask for ideas.

The first thing is, How do you do substances that reflect light based on
thickness, like milk or ice?  When thin, these substances are
semitransparent, but as they get thicker, they turn some color.  Absorbing
media only goes to black, so that's no good.  Can Scattering media do this? 
I hate to think of the render times, which is why I haven't worked with
scattering previously.  Is there some other way?

Second problem.  I need a single feather, one of those poofy kinds with lots
of fronds.  I can do the quill, but doing the fronds has left me blank.  I
can write a macro akin to the hair/grass/whatever macros, I suppose, but I'm
uncertain how to go about it.  Thoughts?

Geoff


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From: Thomas Willhalm
Subject: Re: Looking for ideas
Date: 1 Sep 2000 09:16:28
Message: <qqmzolsgslv.fsf@schlatt.fmi.uni-konstanz.de>
Geoff Wedig <wed### [at] darwinepbicwruedu> writes:
> The first thing is, How do you do substances that reflect light based on
> thickness, like milk or ice?  When thin, these substances are
> semitransparent, but as they get thicker, they turn some color.  Absorbing
> media only goes to black, so that's no good.  Can Scattering media do this? 

According to my physics book, thin milk can be modelled with Mie scattering.
That's why I think that it might be worth trying media type 2 or 3.
I haven't tried this, but you wrote that you were looking for ideas...

> I hate to think of the render times, which is why I haven't worked with
> scattering previously.  Is there some other way?

You might try the sampling method 2 of the MegaPatch. Since milk is 
homogeneous, it shouldn't hurt.

Thomas

-- 
http://www.thomas.willhalm.de/ (includes pgp key)


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From: Warp
Subject: Re: Looking for ideas
Date: 1 Sep 2000 09:59:30
Message: <39afb642@news.povray.org>
Geoff Wedig <wed### [at] darwinepbicwruedu> wrote:
: The first thing is, How do you do substances that reflect light based on
: thickness, like milk or ice?  When thin, these substances are
: semitransparent, but as they get thicker, they turn some color.

  Use fade_distance, fade_power and (in megapov) fade_color.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/


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From: Warp
Subject: Re: Looking for ideas
Date: 1 Sep 2000 10:00:13
Message: <39afb66d@news.povray.org>
Warp <war### [at] tagpovrayorg> wrote:
:   Use fade_distance, fade_power and (in megapov) fade_color.

  In the interior{} of the object, that is.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/


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