"Chris B" <nom### [at] nomailcom> wrote:
> "HarryK" <hko### [at] t-onlinede> wrote in message
> news:web.47c5c35db1099ea68e94e7980@news.povray.org...
> > Hi folks
> >
> > I want to map a prism with n vertices, height_1=0 and height_2=0.001 onto
> > the
> > surface of a sphere. Then I want to create the intersection of the sphere
> > and
> > the mapped prism so that only the prism is visible. Can anybody help me?
> >
> > Thanks in advance
> >
> >
> >      HarryK
> >
>
> Hi Harry,
>
> I'm wondering whether a prism defined using a conic_sweep would do what you
> want.
> You could use it to make a prism that's 0.001 units higher than the radius
> of the sphere you wish to map the prism onto. Then use two spheres to slice
> a 0.001 unit thick spherical layer out of the prism.
>
> For example:
>
> light_source {<2,7.5,-15>, rgb 1}
> camera {location <0,1.4,-1> look_at <0,1,0>}
>
> difference {
>   intersection {
>     prism {
>       cubic_spline  conic_sweep
>       0, 1.001, 14,
>       // Outer Rim
>       <-0.4,-0.4>, <-0.3,-0.3>, <0.3,-0.3>,
>       <0.3,0.5>, <-0.3,0.5>, <-0.3,-0.3>,
>       <-0.4,-0.2>
>       // Inner Cutout
>       <-0.1,-0.3>, <-0.2,-0.2>, <0.2,-0.2>,
>       <0.2,0.4>, <-0.2,0.4>, <-0.2,-0.2>,
>       <-0.3,-0.1>
>     }
>     sphere {0,1.001}
>   }
>   sphere {0,1}
>   pigment {rgb <1,1,0>}
> }


Hi Chris,

your proposal works quite well, when the prism is appriximate
symmetric to the origin. Unfortenately my prism looks like a leaf and is not
symmetric. But I found a solution to map the outline of the prism onto
a sphere and get it as an object. I tried intersection and difference,

helps me?


Thanks in advance
                      HarryK

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