POV-Ray : Newsgroups : povray.advanced-users : isosurface: Does the order of multiple functions matter? : Re: isosurface: Does the order of multiple functions matter? Server Time
26 Mar 2023 21:45:50 EDT (-0400)
  Re: isosurface: Does the order of multiple functions matter?  
From: Alain Martel
Date: 28 Jan 2023 12:27:51
Message: <63d55b17$1@news.povray.org>
Le 2023-01-28 à 05:25, Kenneth a écrit :
> I have an isosuface made from multiple functions that is working quite nicely--
> but I want to rearrange the order of the functions to see the different(?)
> results. The code is complex, so I'll leave out the ugly function details and
> syntax. The following is just pseudo code.
> Right now, it is like this (very simplified):
> isosurface{
> function{A + B + C + D}
> ....
> }
> Only four, thankfully! :-)
> Does the order of the functions matter when POV-ray evaluates them? Or are they
> evaluated 'all at once' regardless of the order?
> If the ordering does matter, what would be the most efficient way to set up
> 'switches' at the beginning of the scene to easily change the order of A,B,C and
> D? Possibilities that occur to me would be some kind of combination of
> #switch/#case, or #if blocks, or select(?), or maybe an array; but I want the
> top-of-code selection process to be relatively easy-- something like
>                #declare FUNCTION_ORDER= <C,A,D,B>;
> .... and without having to make multiple copies of the functions for all of the
> different permutations.
> Any ideas?
> (BTW: #if and #switch/#case do work well in the body of the isosurface, within
> the main function, to at least eliminate certain parts. Probably not good code
> practice, but it causes no problems AFAIK.)

The order should have no effect in this case. As long as you have all 
additions or all multiplications, shuffling the terms won't change the 
end result.
BUT, remember that A-B is different from B-A and A/B is also different 
from B/A.

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