[vtkusers] about vtkStreamer

[Petru Pau]

Hi Jeff,

It seems that I forgot to mention the most important thing: Yes, thank
you, I would very much appreciate your guidance.

I modified the code of vtkStreamTracer, but it seems that the algorithm
always stops when it reaches the border of the first cell. On that cell,
constraining the stream line to the surface works OK.

I added some code that computes one more point, by intersecting the line 
generated
by the last two computed points with the boundary of the cell. After 
that, I switch the current
cell of the vtkInterpolatedVelocityField to the adjacent cell and give 
the control back
to the original code. Now it seems that this last point, computed by my 
code,
is not detected as belonging to an adjacent cell, and the first call to
vtkInterpolatedVelocityField's FunctionValues() returns 0.

I intend to add the computation of one extra point, which should be
in the interior of the adjacent cell (I reckon maybe the algorithm stops 
because
VTK does not really like points on edges), and only afterwards pass the 
control
back to original code. I am not really satisfied with this, but I don't 
know what else
to do to persuade the vtkInterpolatedVelocityField that the point on the 
edge
belongs to the cell.

Most probably there is a simpler way to do things: if so, I would be 
very grateful
for any help.

Petru