Oops, don't ask why I put it in a difference, I was doing a more complicated
example before. Now that part can be deleted.

"clum" <nomail@nomail> wrote:
> I've been doing various things with conic-swept prisms, and I've been
> getting some very unexpected results. I tried reducing my problem to a
> simpler scene file, and though it did not come up with exactly the same
> unexpected results as before, it's still not working as I expected. Here is
> a simple example. With a normal perspective camera, it is a nice square
> pyramid. With a directly overhead orthogonal view, however, the whole thing
> appears green. Though I am not sure, from my previous experimentation I
> believe that only the base is appearing, and not the walls of the pyramid,
> similar to results one receives when using back-face culling with reversed
> normals.
>
> //camera {location <5, 7, 2> look_at <1,0,0>}
> camera {orthographic location <0, 10, 0> look_at <0, 0, 0> up x*3 right z*4}
> light_source {<5,5,5> rgb 1}
>
> difference {
>     prism {
>         conic_sweep
>         linear_spline
>         0, 1, 5,
>         <-1, 1>, <1, 1>, <1, -1>, <-1, -1>, <-1, 1>
>         scale <1, -1, 1>
>         translate y*1
>     }
>
>     pigment {
>         gradient y
>
>         color_map {
>         [0.0 color <0, 1, 0> ]
>         [1 color <0, 0, 1> ]
>         }
>         scale y*.2
>     }
>     finish {ambient .5}
> }

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