Wasn't it Tyler Eaves who wrote:

>5. Lathe/prism hybrid. 
>    It would be super handy to have an object that could be shaped 
>    both in the x-z plane and have an 'edge shape'. I'm thinking of an
>    implementation like this. First the object is built as a prism,
>    then the edge shape is build at each point along the outside, 
>    pointing along the surface normal. This would be really useful
>    for all sorts of archetectural things, such as moldings, tabletops,
>    etc, and I'm sure many organic things as well...

While you're waiting for this to be implemented as a POV primitive, you
can use a parametric isosurface (or, for speed, closely approximated
with Ingo Janssen's param.inc). See my "Prismatic Lathe" example at
<http://www.econym.demon.co.uk/isotut/splines.htm#plathe>

Or you could use my sweepspline.inc to approximate this with a mesh2.
It's at the bottom of  <http://www.econym.demon.co.uk/isotut/more.htm>
It uses three splines to specify the shape - one for the 2d curve that's
used as a cross section, one for the 3d spline that the shape is swept
along, and a 1d spline that describes how the scale varies along the
length of the sweep.
For a lathe/prism hybrid, the 3d spline would be a straight line.

>7. Spline curves
>    What I mean by this is taking a 2d curve, as used in a prism, etc,
>    and drawing it 'along' a spline. Useful for making troughs, gutters,
>    many organic things, etc, especially if a start scale and end 
>    scale could be specified.

While you're waiting for this to be implemented as a POV primitive, you
can use my sweepspline.inc (see above).

If you only want to linearly interpolate between a start scale and end
scale, then use a simple linear spline for the 1d "Waist" spline rather
than a more complicated spline.

-- 
Mike Williams
Gentleman of Leisure

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