[vtkusers] tracing a single point

[tom fogal]

Hi all, I'd like to trace a single point through a vector field, and
find out its location after a specified amount of time.

It may sound like I want a stream line, but thats not exactly what I'm
looking for. I have multiple vector fields affecting a dataset, and I
would like to use one to trace streamlines, and another to affect the
seed point of the stream lines.

I'm not sure if vtkStreamTracer will do this for me. It seems like it
might be conceivable to:

   activate the 'seed point moving' vector field
	set a short length of time for stream line termination
	trace a streamline beginning at "seed"
	"seed" = end of aforementioned stream line
	(somehow?) erase streamline
	activate vector field for 'stream line' tracing
	draw a stream line beginning at "seed"

However I'm not sure I would be able to find the location of the
endpoint for the stream line. 'Erasing' the streamline would probably
entail destroying the renderer and creating a new one, meaning I would
have to do this before all other drawing, but if someone has a better
way or just doubts that approach I'd be glad to hear it.
Finally, determining how long I should let the particle propagate
through the vector field might be difficult, but I think this is a
problem for me and not the VTK list =).

Does anyone have any ideas or comments on how I might want to go about
this?

Thanks in advance for your advice!

-tom