POV-Ray : Newsgroups : povray.bugreports : Is sphere_sweep known to be troublesome? : Re: Is sphere_sweep known to be troublesome? Server Time
20 Apr 2024 10:33:03 EDT (-0400)
  Re: Is sphere_sweep known to be troublesome?  
From: Alain
Date: 13 Mar 2010 12:39:19
Message: <4b9bcdc7$1@news.povray.org>

> This pov file:
>
> ================
>
> #include "colors.inc"
> #include "metals.inc"
>
> light_source {<6, 9, -21>  color White }
> camera { location<0, 0, -3>  look_at<0, 0, 0>  }
>
> sphere_sweep {
>                  cubic_spline
>                  6
>                  <-2.0, 0, 0>  0.05
>
>                  <0.000,0,0>  0.2
>                  <0.025,0,0>  0.2
>                  <0.050,0,0>  0.2
>                  <0.075,0,0>  0.2
>
>                  <3.0,0,0>  0.2
>                  pigment { color White }
> }
>
> ================
>
> Produces two strange artifacts: A disk at the center of the sweep, and a faint
> "halo" or veil which shows as 4 faint hyperbolas centered around the origin.
>
> I have tried tweaking tolerance (for no other reason than I saw that someone
> else was tweaking it to solve a problem) but this does not seem to change
> things.
>
> For a look at MY result when I run this, view this image:
>
> http://riventree.com/archive/bugdata/povray/SphereSweepArtifacts.jpg
>
> (I can't post attachments to this newsgroup)
>
> -Jeff Evarts
>
>
You use very small dimentions that can cause calculations errors, but 
scaling everything up by 1000 just change the location of the disk, it 
make it move left.
Changing the scale don't change the stripes nor the artefacts on the 
right end.
The hyperbola like things are still there, and the ones on the right 
becomes more visible, and I get a parabola like thing on the left.
The "disk" receives and cast shadows. A rotation shows that it's not a 
disk, but a long plane.

It's still there with the latest version: 3.7 beta 35a.



Alain


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