[metapost] Re: new is_clockwise routine
Laurence Finston
lfinsto1 at gwdg.de
Sun Nov 27 13:32:29 CET 2005
On Sun, 27 Nov 2005, Werner LEMBERG wrote:
> I thought that the idea of my code is quite obvious, but apparently it
> isn't. Here's the used algorithm.
I don't usually find reading other people's code enjoyable. Thank you for
the explanation in plain English.
>
> 1. Find a point P on the path which has a non-zero direction.
[...]
> This method completely avoids any problems with the geometry of Bézier
> curves.
It seems like a roundabout way of doing it, which is the impression I had
before. You asked for comments, so I explained how I plan to go about
it, if and when I reach this point. If it's not helpful to you, please
disregard it. I don't see any problems with the geometry of Bezier
curves. One can convert the representation using control points into a
polynomial and manipulate the latter using straightforward and
well-documented methods.
> > A more serious problem is determining whether the curve loops or
> > changes direction between two values of 't'.
>
> As mentioned in my last mail, I assume that the curve doesn't
> intersect itself. It's not needed for my particular problem, and it
> makes life much simpler.
I try to find general solutions without losing touch with reality.
Laurence
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