Visualisation question

[pahsieh at usgs.gov]

> 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.

Good luck



--------------------------------------------------------------------
This is the private VTK discussion list. Please keep messages on-topic.
Check the FAQ at: <http://public.kitware.com/cgi-bin/vtkfaq>
To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
<majordomo at public.kitware.com>. For help, send message body containing
"info vtkusers" to the same address.
--------------------------------------------------------------------