[vtkusers] Picking bundles of streamlines

[Ralph Brecheisen]

Hi,

I have a vtkPolyData object containing a bundle of streamlines that are
colored according to some scalar property stored in each streamline point.
The coloring of the streamlines results in relatively smooth transitions
along the bundle. I would like to be able to pick a point somewhere on this
bundle and retrieve the scalar property of the streamlines at that point. In
principle, I could try to pick individual streamlines but since streamlines
in the immediate neighborhood of the picked point probably share the same
scalar property a different picking method might be suitable also.

Problem is, which method could I use? I tried the vtkPointPicker but this
one always returns a point ID = -1. I looked inside its IntersectWithLine()
method and printed the ray endpoint coordinates and they seem to be
somewhere complete different than where I clicked (if I mentally translate
my mouse screen position to a world position). I'm not sure therefore
whether these endpoints are in world coordinates. The alternative pickers,
such as vtkPropPicker or vtkRenderedAreaPicker also do not really fulfill my
purposes (I think) because they just give me the prop, which is the whole
streamline bundle, instead of the point ID(s) in the neighborhood of the
picked point.

Anybody have experience with picking streamlines? Or points on dense bundles
of streamlines?
Some advice would be most welcome!

Grtz!

Ralph

-- 
"The only Zen you find on the tops of mountains is the Zen you bring up
there."
- Robert M. Pirsig

-------------
Ir. Ralph Brecheisen
Biomedical Image Analysis (BMIA)
Biomedical Engineering @ Technical University of Eindhoven
Den Dolech 2, 5600 MB
Eindhoven, the Netherlands
Tel: +31-40-2475571
E-mail: r.brecheisen at tue.nl, ralph.brecheisen at gmail.com
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