From: "scam" <sca### [at] mailusyd.-sans.spam.-edu.au>
Date: Tue, 30 May 2006 09:00:54 EDT

Note to moderator: This was posted in povray.general, and was
confirmed by
two seperate people:
http://news.povray.org/povray.general/thread/%3Cweb.44779e5a358a67bc5c947f990%40news.povray.org%3E/

Rendering scenes containing sphere sweep objects which are either very
large or very small leads to large artifacts. Different artifacts are
seen depending on the size of the object, and the type of spline used
(linear, cubic etc). A simple test scene is reproduced below.

The problem has been confirmed to exist in the windows 3.6.1b and the
3.7 beta 13 versions and the official linux 3.6 binaries. It is not,
however, present in the official linux and windows 3.5 binaries.

The parameter 'myscale' scales the object and the cameras position
proportionally. For values of 'myscale' less then 0.01, and greater
then 10, various artifacts are seen. The artifacts cannot be removed
by varying the value of 'tolerance'.

#include "colors.inc"

#declare num_phi1=10;
#declare myscale=0.01;

sphere_sweep {
    cubic_spline
    num_phi1+1,
    #declare _phi1 = 0;
    #while (_phi1<=6)
         #declare p1 =<sin(_phi1),-cos(_phi1),0>*myscale;
         p1,0.1*myscale
         #declare _phi1 = _phi1 + 6/num_phi1;
    #end
    tolerance 0.01
    pigment {Red}
}

background{White}

camera {
    location <0.0, 0, -1>*3*myscale
    look_at <0,0,0>
}

light_source { <0, 0, 0> color White }

Post a reply to this message