On 10/29/06, William Henney <[EMAIL PROTECTED]> wrote:
> > Just a last one:
> > I really need to implement MetaPost-like Bézier curves, "z0..z1" draws a
> > Bézier curve from z0 to z1 without having to calculate the control
> > points. Is there something similar in PyX and if not, where to find any
> > reference ?
>
> As far as I know, there is nothing built in to PyX for doing this. It
> would be great if there were!
>
> If you want to implement this yourself, then the wikipedia article
> looks like a reasonable general introduction
> (http://en.wikipedia.org/wiki/B%C3%A9zier_curve). The way metapost
> does it seems to be reasonably well documented - see
> http://www.tlhiv.org/MetaPost/documentation/, particularly
> Metapost_Curves.pdf
>

I just found a better reference. This is John Hobby's original paper
from 1985 on the algorithm that got used in metapost:
ftp://db.stanford.edu/pub/cstr/reports/cs/tr/85/1047/CS-TR-85-1047.pdf

You also might want to look at how this is done in asymptote
(http://asymptote.sourceforge.net). They seem to have reimplemented
Hobby's algorithm and also have generalized it to be invariant under
3D transformations.

Cheers

Will

-- 

  Dr William Henney, Centro de Radioastronomía y Astrofísica,
  Universidad Nacional Autónoma de México, Campus Morelia

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