Dan Connelly wrote:
> 

> 
> 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.
> 
> [some code].......

bug or feature?, that is here the question (freely by W. Shakespeare)

fact is, that in case of conic_sweep, you have by no way the freedom in
definition of the corner points of your prism, the docs want to make
believe you.
This all has to be done in a way, that at y = 1 your corner points ought
to have uv coordinates in a range between <-0.5, 0.5> and <0.5, 0.5>,
otherwise the inside of your prism apparently will be turned out and you
will get the open truncated pyramide and the misplaced face, you have
observed.
You should scale your prism afterwards.

Try out this, it works:

//pov code:

prism {linear_spline conic_sweep 1, 0.7, 5
       <-0.5, -0.5>, <0.5, -0.5>, <0.5, 0.5>, <-0.5, 0.5>, <-0.5, -0.5>
       pigment {Blue}
       translate <0, -0.85, 0>
       scale <5, 2, 3>
       rotate <0, 0, 180>
       }

//end of pov code


ReVerSi

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