POV-Ray : Newsgroups : povray.general : problem: repeating rand patterns using seed in animation : Re: problem: repeating rand patterns using seed in animation Server Time
30 Jul 2024 18:10:45 EDT (-0400)
  Re: problem: repeating rand patterns using seed in animation  
From: Kenneth
Date: 25 Jan 2009 03:45:00
Message: <web.497c25c4b528db0df50167bc0@news.povray.org>
Alain <ele### [at] netscapenet> wrote:

> You can try moving some large, non-constant, distance between your seed values.
> Something like:
>
> seed(pow(31*pi*clock,frame_number)}
>

I had to think about this one for a little while; but rather than over-strain my
brain, I decided to simply run it, to see what would happen.  The result is very
odd: In my 100-frame test animation (pulling only one rand() value per frame),
my moving sphere STOPS moving at about frame 10. I'll try and dissect the
problem here.

Let's see: Since the clock is going 0 to 1, that would put the clock at .10
Then pow(31*pi*.10,10) = 4.2844 X 10^23

(I had to #debug the scene to find that.)

A whoppingly high value, probably over the limit of what seed (or even POV) can
process. The same thing happened during my own trial-and-error phase as well,
several times. Some seed equations just make POV go bonkers.

KW


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