[vtk-developers] vtkPicker, vtkCellPicker, vtkPointPicker and vtkCompositePolyDataMapper

[Andreas Buykx]

Hi all,

I have pipelines that process vtkMultiBlockDataSet and I want to map those using vtkCompositePolyDataMapper. This works fine, except that picking the rendered composite data set causes a crash. This is because vtkPicker, vtkCellPicker and vtkPointPicker assume that vtkMapper always maps a vtkDataSet which is not true in this case. Specifically vtkCellPicker::IntersectActorWithLine and vtkPointPicker::IntersectWithLine will crash, and since vtkPicker::DataSet may get set to 0, any callers fo vtkPicker::GetDataSet that expect a non-null data set will run into problems as well. AFAIK there is no picker implementation that works well with composite data sets, is there?

This issue is a blocker for me to integrate vtkCompositePolyDataMapper, so I am going to fix this either by patching our own VTK build or contributing a change to VTK. To do this the right way (I prefer to contribute), I would like some advice/steer on how to fix this issue.

A minimally invasive approach would be to add members to vtkPicker to store a vtkDataObject and a flat index of the picked dataset, and set those in case the mapper contains a composite dataset. The IntersectWithLine methods would have to be refactored to allow iterating over the blocks of a vtkDataObject.

Kind regards,
Andreas



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