[vtkusers] vtkSelection

[Bryn Lloyd]

Hi David,

Thanks a lot for your reply.

> 
> You might not need to use AreaPicker. It's job is to pick entire
> Props, you seem more interested in cells and points on a particular
> prop. VisibleCellSelector can determine props on its own if you want
> it to, and the FrustumExtractor could be reapplied to all the props in
> the scene if you don't end up using AreaPicker to narrow down the
> list.
> 
> The InteractorStyle is useful for giving the user a rubber band to
> draw on the screen with, so you might as well use that part.
> Converting that 2D rectangle into a 3D rectangle is only needed if you
> are selecting through. The AreaPicker can help with that if you need
> it.

I need to select through (i.e. non-visible). So I could use the 
AreaPicker to calculate the Frustum and pass it to the 
vtkExtractSelectedFrustum object in order to select the points or cells?

So vtkExtractSelectedFrustum knows the Frustum, how do I setup the 
vtkSelection object?

My guess is:

   selection->SetContentType(vtkSelection::FRUSTUM);
   if(mode==POINTS)
     selection->SetFieldType(vtkSelection::POINT);
   else
     selection->SetFieldType(vtkSelection::CELL);

But what about the SetSelectionList? Is this where I need to set the 
parameters of the Frustum (again)?, or will vtkExtractSelectedFrustum 
ignore this list, since it already knows the Frustum?



> Take a look at TestExtraction first to investigate what Selections and
> Extraction are and how to use them,
> 
> Then take a look at TestAreaSelections to see how to use them to grab
> things that the user identifies behind the rubber band.

I have looked at these tests, and the java example 
Examples/Infovis/Java/Focus.java.

There are, however, many different combinations of 
vtkSelection::SetContentType, vtkSelection::SetFieldType and it is not 
clear how the SelectionList must be created for each situation, or if it 
must be set at all.


Thanks,

Bryn