[vtkusers] vertex add function // constrained decimation

[John Biddiscombe]

>>>
1. Is there a vertex add function available in vtk ?

I want to use it after delaunay and decimation, in order
to add some constraints to the mesh.

2. Is there a way to constrain decimation using:

    2.1 vtkDecimatePro ?

    2.2 vtkClustering ?

By constraints, I mean force the decimation to keep
some exact points, which could be a isoline, a polygon
contour, etc...
<<<

Not really, no. You can constrain the triangulation with a polyline etc, but
the decimation will possibly remove it.
If you examine the decimate code quite carefully, you will see that a
priority queue is used to store each vertex which has been considered for
removal, in principle it'd be possible to rework the code to allow a
pointdata array to be assigned to the mesh where the values at each point
were a "desirablilty" value (say 0->1) where 0 meant allowed to remove and 1
forbidden. This would permit regions to be decimated more or less brutally
depending upon uer requirements.
It'd be a lot of work, I expect.

JB