"Chris B" <nom### [at] nomailcom> wrote:
> "Jovian Ghost" <nomail@nomail> wrote in message
> news:web.4ad1312e6c73c7c683b0b960@news.povray.org...
> > Thanks for the replies everyone!
> >
> > I think that using spheres for corners and cylinders for edges is actually
> > a
> > good idea, and probably the easiest for me to do. I do believe I may be
> > overstepping my bounds a bit.
> >
> > But I also wanted to try my second idea (actually the link in my second
> > post)
> > which is making a spline, then putting spheres that follow that spline.
> > Then
> > drawing a cylinder from the top spline to the bottom.
> >
> > That will work, but unfortunately I can't get my cubic spline to look
> > right, and
> > for some crazy reason, POV-Ray only allows Bezier curves for prisms, and
> > not for
> > anything else???
> >
> > Is there an easier way I can model my cubic spline, rather than
> > trial-by-error?
> > I tried exporting a spline from Inkscape but unfortunately that only does
> > Bezier
> > curves.
> >
>
> There is an easy way: There are spline editors available that can directly
> generate cubic splines (e.g. Spilin, which is a small utily application for
> drawing POV-Ray and VRML splines. See
>
http://news.povray.org/povray.binaries.utilities/thread/%3C48cf4dea@news.povray.org%3E/).
>
>
> You can also do the job with Inkscape. It's a little more complex, but if
> you've already got the shape you want in Inkscape, you might want to give
> this a go:
>   o  Use the 'edit points' selector in Inkscape to select your shape
>   o  Ctrl-A to select all points
>   o  Add sufficient intermediary points to the curve so that it won't matter
> what form of spline you eventually use, it'll follow the same path anyway
>   o  Save as a POV-Ray prism object
>   o  Extract the locations of the points, ignoring the control points
>
> Inkscape writes out the bezier spline with 4 coordinates per line. The outer
> two points are the control points and the inner two points are points on the
> curve. Fortunately it aligns them nicely, making it mind-numbingly easy to
> select columns of data. If you open the file in an editor that supports
> columnar editing you can simply pick out the middle two columns to use, or
> pick out the outer two columns to delete.
>
> In the POV-Ray Windows editor you can use the mouse with Ctrl-Shift to
> select columns of data:
>   o  Select the first column of control points and hit delete.
>   o  Select that last column of control points and hit delete.
>   o  Delete the comma following the last point
>   o  Change the spline type to linear
>   o  Update the number of control points (halve it)
> Hey presto you've got a linear spline that follows your curve and that you
> can easily redefine as a spline function. You can achieve similar results
> using less points by using a cubic spline, but then you'll need to deploy a
> bit of mental effort to add the necessary control points at the start and
> end of the spline.
>
> Note that, when selecting large blocks of data in columns using POV-Ray you
> can click at the start point then use the mouse with the scroll bar to bring
> the end-point into view so that you can Ctrl-Shift-LeftMouseClick it. This
> method of scrolling avoids moving the current position of the caret in the
> text, whereas scrolling using the keyboard moves it, making the whole
> experience less satisfying  :-)
>
> Hope that helps,
>
> Regards,
> Chris B.

Thanks Chris B!
Unfortunately I'm running the Linux version of POV-Ray, so I can't use Spilin; a
quick Google reveals it's a Windows app.

In my understand is correct, your Inkscape method describes creating a curved
line with a lot of straight lines.
I would prefer to use curved splines if I can.

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