"Chaanakya" <nomail@nomail> wrote:
> Warp <war### [at] tagpovrayorg> wrote:
> > Chaanakya <nomail@nomail> wrote:
> > > I was trying to create half of a hollow cylinder (both ends open).  I tried
> > > using CSG with an intersection, and that gave me a half a hollow cylinder, but
> > > I'd like to not have a plane on the end.  That is, I'd like essentially a curved
> > > plane (the side of the cylinder without the endcaps).  Is there some
> > > transformation I could use on, for example, a box to achieve this?
> >
> > Just make a difference of the cylinder and another cylinder with a slightly
> > smaller radius and which is a bit longer ther the first cylinder.
>
> Thanks!  That lets me control the thickness of the resulting object.  How would
> I cut it in half?
>
> - Chaanakya

This is a bit weird....the shell seems way too thick when I render this:

#version 3.6;
#include "colors.inc"

global_settings {
  max_trace_level 256
  ambient_light White
  assumed_gamma 1.0
}

camera {
  location <10,0,0>
  look_at <0,0,0>
  //rotate <0,0,-clock*90>
}

light_source {
  <0,100,0>
  color White
}

plane {
  y, -10
  pigment { hexagon Green, White, Blue }
}

difference {
  cylinder { <-1,0,0>,<1,0,0>,1}
  cylinder { <-1.00003,0,0>,<1.00003,0,0>,0.99999999}
  pigment { color Red }
}

The shell should be barely visible, but it's quite thick.  Why?  Is it floating
point error?

- Chaanakya

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