Visualisation question

[Gavin Tabor]

Will Schroeder wrote:
> 
> To add to Paul's comments: vtkDelaunay3D does a pretty good job of constrained Delaunay triangulation...it's a relatively new feature added within the last year or so.

Looking at the triangle.c program (or at least the web page) it 
seems to include a feature which prevents the trangulation going
outside the boundary defined by the initial specified points. I
assume that vtkDelaunay2D doesn't share this feature? I need to
mesh the inside of a contour which is not always convex, so this
seems to be what I need.

Gavin

> Will
> 
> At 08:04 AM 5/2/00 -0700, pahsieh at usgs.gov wrote:
> 
> > > There are various algorithms for contouring : you have data at
> > > specified grid locations, and you generate (in 2-d) a line which
> > > represents all points with a given value.
> > >
> > > Question : How would one go the other way? I have a contour line
> > > representing the boundary between two regions. How can I generate
> > > the data set on a set of regular points that would generate this
> > > contour line? (Is there even a unique solution?)
> >
> >I have done this by constrained Delaunay triangulation. Assuming
> >each contour is a polyline (defined by points connected by straight
> >line segments), a constrained Delaunay triangulation will create
> >triangles such that the contour line segments are triangle edges.
> >Then, for each grid point, find the triangle that contains the
> >point and estimate the value by interpolation.
> >
> >To perform constrained Delaunay triangulation, I use the
> >Jonathan Shewchuk's program triangle.c, which can be downloaded
> >from
> >
> >http://www.cs.cmu.edu/~quake/triangle.html
> >
> >I think vtkDelaunay2D performs only unconstrained triangulation.

-- 

Dr. Gavin Tabor
School of Engineering and Computer Science
Department of Engineering
University of Exeter
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