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18 Nov 2024 07:16:58 EST (-0500)
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From: ascscr
Subject: Artifacts on colormap experiments
Date: 18 Sep 2002 16:35:04
Message: <web.3d88e285cb77a6ae7dc403f50@news.povray.org>
Hi,

I did a very simple (although somehow brain damaged) thing:

A simple scene, haveing a box. which has the following pigment:

      pigment {
        wood
        frequency 5
        colour_map {
            [0, red 1 green 1 blue 1 transmit 1.0]
            [0.5, red 0 green 0 blue 0 transmit 1.0]
         }
      }
This resulted in an invisible box (no surprise) and a light blue
spot at the ground - which was a surprise.

Anybody knows why this looks like it looks?

Thanks

Alexander


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From: Christopher James Huff
Subject: Re: Artifacts on colormap experiments
Date: 18 Sep 2002 17:38:00
Message: <chrishuff-8B99CB.17360818092002@netplex.aussie.org>
In article <web.3d88e285cb77a6ae7dc403f50@news.povray.org>,
 "ascscr" <asc### [at] gmxde> wrote:

> This resulted in an invisible box (no surprise) and a light blue
> spot at the ground - which was a surprise.
> 
> Anybody knows why this looks like it looks?

You had the box sitting on a ground plane? Did you make sure the bottom 
of the box wasn't coincident with the plane? I'm betting you had a nice 
blue sky background?

This is my guess as to what happened:
The camera ray went through the side of the box, and the first thing it 
hit on the circle area was the bottom of the box. When POV continued 
from that point, the plane intersection was rejected because it was too 
close to the beginning of the ray (it does this so transparency and 
reflection work right), so it went on to your sky. Outside the circle, 
the opaque ground was hit first (precision error) and the ray just 
stopped there.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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