POV-Ray : Newsgroups : povray.advanced-users : Color maps : Re: Color maps Server Time
21 May 2022 15:45:07 EDT (-0400)
  Re: Color maps  
From: William F Pokorny
Date: 22 Mar 2021 07:27:30
Message: <60587f22$1@news.povray.org>
On 3/21/21 9:56 AM, Bald Eagle wrote:
> So, I have been working with functions and patterns for a while now, and 
> aside from not having vector functions to easily create color values 
> with, I have run into an issue with the way POV-Ray maps things - 
> colors, pigments, textures.
> 
> Since I haven't experimented extensively with these mapping mechanisms 
> or gone through the source code to see exactly how they are handled, I 
> as far as I know, they only handle values in the range from zero to one.
> 
> I'm interested in knowing if anyone has done any work that contradicts 
> this notion, or to hear how I might use negative numbers, large numbers, 
> or ways to get around the auto-wrapping-around of the color map.  I'd 
> like to subtract part of one color channel from the overall result of an 
> average {} pigment using a negative value, or saturate the color (to 
> white) by allowing large values.
> 
> Any data would be helpful.
> 
> Thanks!

The short answer if you are using v3.7 or v3.8 more or less stock, is 
you can use the 0-1 map range only(1).

(1) - And even with this there are some general issues/bugs.

For more information look at the series of postings working backward 
from to the first few starting here:

http://news.povray.org/povray.beta-test.binaries/thread/%3C5fdfc14f%40news.povray.org%3E/

Bill P.


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