"F. Hydrant" <dpe### [at] scphyskyoto-uacjp> wrote:
> Subtracting two isosurfaces to create a shell, portions of the shell where the
> inner (subtracted) surface should be visible are completely transparent.  Some
> shadows are cast by the invisible shell.  Other shapes I've tried do not do
> this.
>
> I've tried this on Linux (Kubuntu 9.10 fully patched, POV-ray 3.6.1 as compiled
> by Debian) and Windows Vista (32-bit fully patched, POV-ray 3.6.2 and
> 3.7.beta.35a) on a P4 dual core 3GHz, 3GB RAM computer, and on WinXP Home
> (POV-ray 3.6.2 and 3.7.beta.35a, Core 2 Duo 2.33GHz, 1GB RAM, Japanese).
>
> Sample code:
>
>
> background { color <0,0.1,0.2> }
>
> camera {
>   orthographic
>   location <2, 6, -20>
>   right <8, 0, 0>
>   up <0, 6, 0>
>   look_at <0, 0, 0>
> }
>
> light_source { <50, 50, -20> colour <1,1,1> }
> light_source { <-20, -5, -10> colour <1,1,1> }
> light_source { <-2, 5, -10> colour <1,1,1> }
>
> difference{
> isosurface{
>     function{ pow(x,2) + pow(y,2) + pow(z,2) - pow(2.5,2) }
>     contained_by { sphere { <0,0,0>, 2.51 } }
>     max_gradient 5.1
>     pigment{color <1,1,0>}
>            }
> isosurface{
>     function{ pow(x,2) + pow(y,2) + pow(z,2) - pow(2.4,2) }
>     contained_by { sphere { <0,0,0>, 2.51 } }
>     max_gradient 5.1
>     pigment{color <1,1,0>}
>            }
>   box { <0, -5, 0>, <5, 5, -5>
>     rotate <0, 45, 0>
>     pigment{ color <1,1,0> }
>        }
> }
>
> // I found the following helpful in demonstrating the issue
>
> difference{
>  torus{ 1, 0.2
>       pigment{ color <1,0,0> }
>       translate <0,-2.35,0>
>        }
>   box { <0, -5, 0>, <5, 5, -5>
>     rotate <0, 45, 0>
>     pigment{ color <1,0,0> }
>        }
> }

tanx...
its amazing information

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