Le Sat, 16 Aug 2008 21:01:43 +0200, Smellenbergh a modifié des petits
morceaux de l'univers pour nous faire lire :

> When using at least *two* light sources together with at least *three*
> isosurfaces, the surface clipped by a spherical container becomes
> transparent and dotted.

This scene can be reduced to 1 light source and 1 isosurface when 
reducing the bounding threshold.  (Rendered and comfirmed on beta25, 
linux amd64... no source yet for beta28 :-( )

Seems to be tied to bounding activation and containment by sphere.
(here, the container is also truncating the function, but that is 
allowed, right ?)


Bogus:
povray -Ibug.pov -W640 -H480 +A0.001 +MB1

Correct (at least less noisy sphere):
povray -Ibug.pov -W640 -H480 +A0.001 +MB4

//start scene
#version 3.7;

camera {location  <0,0,-18> look_at <0,0,0> angle 55}

background {rgb <.8,0,0>}

light_source {<-30, 100, -30> color rgb 0.6}

#declare f_sphere = function { internal(61) }
#declare f_rounded_box = function { internal(60) }
isosurface {
  function { f_rounded_box(x, y, z, 0.3, 0.8, 1, 0.8)  }
//  contained_by{box{<-0.85, -1.4,-0.25>,<0.85, 1.4, 0.85>}}
  contained_by{sphere{0,0.9}}
  pigment {rgb 1}
  scale 3
  translate x*4
}

//end scene

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