Dan Connelly wrote:

> I am having difficulty with the linear spline prism
> with a conic sweep.  But before I issue a bug report,
> I would appreciate it if someone could give this
> test script a quick run to make sure I'm not doing
> something stupid.....
>
> This is supposed to be a closed truncated pyramid,
> but instead I get an open truncated pyramid and a misplaced
> face.  But please, check for yourself.
>
> I am running 3.1r1 W95..... but I suspect this is a
> core renderer problem (platform independent).
>
> Dan
>
> ========================================
>
> #declare V0 = <0, -3, 0>;
> #declare V1 = V0 + <-5, 9, -8>;
>
> camera {  location V1  look_at V0}
>
> light_source {  V1  color rgb 0.5}
> light_source {  V1 * <-1, 1, 1>  color rgb 0.5}
>
> prism {  linear_spline  conic_sweep
>   -4, -2,  4,
>   <1, 1>, <-1, 1>, <-1, -1>, <1, -1>
>   //open
>   pigment { color rgb 1 }  finish { diffuse 0.5 ambient 0.5 }}
>
> ---
> http://www.flash.net/~djconnel/

  I can verify your problem but cannot explain it. If you change

prism {  linear_spline  conic_sweep
  -4, -2,  4,

to

prism {  linear_spline  conic_sweep
  -4, -1,  4,

it begins to appear as you want it to but the height
of the opening is higher and smaller  than you seem
to want.

The amount greater than -1 you use the more prevelent
the defect.

Ken Tyler

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