clipka <ano### [at] anonymousorg> wrote:
> Am 26.07.2012 16:02, schrieb Chaanakya:
> > "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?
>
> What you're seeing is just a perspective effect; change the camera
> location to e.g. <10,3,0> and light source position to e.g. <100,100,0>
> to better see what's goung on.

Ah I understand.  Thank you!  Is there any way to now cut that object in half
(without ending up with a plane "capping" it)?

- Chaanakya

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