[Paraview] selected points change when clip plane changes

[Zenker, Dr. Matthias]

> > thank you for the hint, but it doesn't seem to do what I want.
> > My workflow was:
> > 1. Display 3D geometry, color by temperature
> > 2. Apply clip filter
> > 3. Select some points
> > 4. Apply extract selection filter
>
> This should copy your selected points into a new object.
> Nothing with you do with the clip filter should alter it.

Well, for me it doesn't work this way. When I move the clip plane and hit Apply, the selected points have changed positions also in the Extract Selection view. I use ParaView 3.12.0-RC2 under Windows XP. 3.14.1 behaves the same way, but doesn't allow me to add points to a selection by holding the ctrl key, and crashes more often than 3.12.0-RC2.

> > 5. Change position of plane of clip filter
> > Result: After step 5, the points are at totally different locations.
> > Does ParaView renumber the points when the clip filter is applied? IMHO it
> shouldn't...
> >
>
> Yes every vtk filter creates a new object when the filter's parameters
> change. Especially when the topology changes (consider the extreme
> case of clipping away everything), there is no guarantee of
> correspondence between indexes in the old and new result. That is why
> the active surface selection, which picks out individual cells/points
> by index, will change.

Hmmm, IMHO this is counter-intuitive for the user, and would be worth improving...

Matthias


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