[vtkusers] How to get boundary points???

[Larry]

Thank you very much for you kind help!

The Graham Scan work fine, but still not exactly what I want, in the case of
following
*******************
*                                  *
*    ************      *
*    *                    *      *
****                    *****
I t will give the outter rectangle(following diagram) rather than the
acutally boundary above.
*******************
*                                  *
*                                  *
*                                  *
*******************

Do you have any idea about this?

Thanks Again!

Larry.

----- Original Message ----- 
From: "david e ignacio" <davidi at cs.uchicago.edu>
To: "Larry" <larry74 at 163.com>
Cc: <vtkusers at vtk.org>
Sent: Monday, February 23, 2004 7:09 PM
Subject: Re: [vtkusers] How to get boundary points???


> I don't know if there is a prebuilt class that does this.  If you want
> to implement this yourself, you can look up such things as "Graham's
> Scan" and also Jarvis's March.  They are fairly simple algorithms that
> run in O(nlogn) and O(nh) where h is the number of points in the hull.
> Let me know if you need more help than that.  If I ever get some free
> time from my schoolwork and this is still needed, I can put something
> together.
>
> Let me know
> Dave
>
> Larry wrote:
>
> > Hello, everyone!
> > I have a vtkPolyData, which is in my case actually a bunch of triangle
> > cells lie on the same plane, now I want to get the boundary that
> > enclose all
> > the triangles.
> > Simply to say, that I have some points, and I'd like to figure out the
> > boundary points.
> >
> > Is there any way in vtk to do that?
> >
> > Thanks!
> >
>
>
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