Chris Huff <chr### [at] maccom> wrote:
> Why use the macro when splines are available as a built-in feature? Are
> there some special features it has?

In a word, Yes.  I knew spline functions were available in POV patches when
I was working on my Spline macro file, and I expected that these would find
their way into a future official version of POV-Ray.  Because of this, I
didn't want to spend my time creating something that would very quickly
become obsolete (after all, I already had a spline include file that seemed
to serve people quite well).

As a result, simply calculating splines positions given a list of points is
the very least the file does.  Firstly, it offers the ability to create all
the cubic interpolating splines, from Catmull-Rom to cardinal right through
to Kochanek-Bartels (TCB) splines, as well as hermite and Bezier splines.
This gives much more control over the shape of the spline, and allows you to
explore all sorts of curves that may pass through a single set of points
(see the first page of the Spline Macro tutorial at
http://www.geocities.com/ccolefax/spline).

Also, as Warp mentioned, it includes a full set of sampling functions so you
can find the length of splines, create splines tensioned to fit a specified
length, and returns points evenly spaced along a spline.  It also includes a
caching function to speed up the usage of sampled splines.

On top of that, the system includes a set of macros that fully automate the
use of splines for animation and object creation, which can be customised
partly or completely.  Alan has used various features (the Bezier spline,
tensioning, sampling, custom object creation macros), and while it's true
similar results could have been achieved using the internal spline function,
to have things like the evenly distributed glows would entail recreating
much of what my macro file already does!

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