index array or boolean array from vtkSelection

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Hello, I would like to get a numpy array of integer indices or a numpy boolean mask from a vtkSelection object in Python :

def get_visible_vertices(plotter, pv_mesh):
    # perfrom the automatic picking
    selector = vtk.vtkOpenGLHardwareSelector()
    selector.SetFieldAssociation(vtk.vtkDataObject.FIELD_ASSOCIATION_POINTS)
    selector.SetRenderer(plotter.renderer)
    selector.SetArea(0,0,plotter.window_size[0],plotter.window_size[1])
    selection = selector.Select()
    # mask = selection.ExtractBooleanMask() <- How to do this ?
    # vertex_indices = selection.ExtractVertexIndices() <- or this ?

plotter is a an object from Pyvista which is a wrapper around vtk render as far as I understand. pv_mesh is a PolyData from Pyvista which should be a wrapper around vtk’s PolyData

The c++ documentation seems overwhelming to me I do not know where to start, sorry.

Thanks

PS : I know that the vtkSelection I get is “correct” because I can plot it with the following code :

    extractor = vtk.vtkExtractSelection()
    extractor.SetInputData(0, pv_mesh)
    extractor.SetInputData(1, selection)
    extractor.Update()
    pv.wrap(extractor.GetOutput()).plot()

And i get this plot which is coherent (the red drawings represents the camera when selecting the visible vertices):
image
image

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