[vtkusers] streamlines: behavior at edges

[Petru Pau]

I have studied the streamline generation implementations, both vtkStreamer
and vtkStreamTracer. Here's a question for the experts:

As the streamline goes closer to the edge of the cell, the influence of the
distant vertices of the cell diminishes, until only the endpoints of the
touched edge contribute with their vectors. Is this strategy correct?

I doubt the correctness of this strategy from a very simple reason: If one
has a quad, one can use it as is or one can triangulate it. The two 
situation
generate completely different streamlines. Intuitively this should not 
happen,
because the vector field and points geometry have not been altered.

Petru