POV-Ray : Newsgroups : povray.beta-test : bug in sphere_sweep for removing parts of an object : Re: bug in sphere_sweep for removing parts of an object Server Time
29 Mar 2024 03:23:01 EDT (-0400)
  Re: bug in sphere_sweep for removing parts of an object  
From: Mike Williams
Date: 15 Dec 2001 09:15:31
Message: <WeTy4NAfp1G8EwLx@econym.demon.co.uk>
Wasn't it Andrel C. Linnenbank who wrote:
>> 
>> >Second point is that I used a parameterization for the sizes
>> >of the spheres that depended on the clock to generate an animation.
>> >It was a rather complex formula. I now use a different method where
>> >I generate an different include file for every frame. The reason
>> >is that this seems to be much faster. Apparently the formula
>> >is computed for every pixel in stead of ones per frame. I
>> >think some caching may improve the speed of rendering.
>> 
>> I can't reproduce that with simple formulae that use the clock.
>> You're not using functions by any chance are you?
>
>I meant that I used things like 
>
>sphere_sweep {
> catmull_rom_spline
> 11,
> <-0.785398,0.000000,0.000000>,1-(exp(-(2-sin((clock)*2*pi))*4)*25),
>.
>.
>.
>
>(or worse) does that count as using functions?

No. All that stuff gets evaluated at parse time. It doesn't affect the
speed of the rendering. 

The various frames take different amounts of time to render, but only
because the object varies in size. In particular, on my machine, the
time to render a frame with clock=0 containing lots of things like
  <-0.785398,0.000000,0.000000>,1-(exp(-(2-sin((clock)*2*pi))*4)*25),

renders in exactly the same time as one containing things like 
  <-0.785398,0.000000,0>,0.991613,

-- 
Mike Williams
Gentleman of Leisure


Post a reply to this message

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.