POV-Ray : Newsgroups : povray.bugreports : Is sphere_sweep known to be troublesome? : Re: Is sphere_sweep known to be troublesome? Server Time
12 Jun 2024 12:05:29 EDT (-0400)
  Re: Is sphere_sweep known to be troublesome?  
From: Kenneth
Date: 18 Mar 2010 11:30:00
Message: <web.4ba246a52e5cb7c265f302820@news.povray.org>
Warp <war### [at] tagpovrayorg> wrote:
> Kenneth <kdw### [at] earthlinknet> wrote:
> > [When using a cubic_spline] the ENTIRE scene renders slower--every pixel.
> > Moving the camera way back--so that the sphere_sweep is barely visible in the
> > scene--doesn't change this; in fact, the scene renders even *slower*, which
> > is completely counter-intuitive.
>
>   Manually specifying a bounding box for the sphere sweep object should fix
> that problem.

Did a test, and that does indeed work; the OP's object renders MUCH faster, and
the artifacts are confined to the bounding shape. (Remove_Bounds=on needs to be
in the INI file, though; I don't know how that might affect 'bigger' scenes.
With it off--the default--POV issues a non-fatal warning, "Unnecessary bounding
object removed" and eliminates the bounding object.)

Something else: With Remove_Bounds=off, but by changing Bounding_Threshold to
zero (the default in v3.6.1 is 3), it also significantly speeds up the render.
Seems that there *is* a bounding object around the sphere_sweep in this
case...perhaps a 1-unit box, I can't tell. It doesn't eliminate *all* of the
hyperbolas and 'plane', but cuts off most of them.

My tests/results in v3.6.1 may not be the same as in 3.6.2 or the later betas;
the bounding algorithm was changed/improved, IIRC.

The nice thing about the OP's sphere_sweep is that it's a simple 'linear' one.
With a snaking, sinuous sphere_sweep, these bounding tricks would have a hard
time containing the artifacts.

Ken


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