Effectively, having 2 vtkSphereSource with vtkPolyDataMapper and vtkActor with transparency appears correctly. But obviously I need to have a vtkAbstractWidget (with transparency, obviously too…).
In reality, I don’t use vtkSphereWidget2 and vtkWidgetRepresentation, but my own widget and representation, inherit from vtkAbstractWidget and vtkSphereRepresentation. Is there a way to workaround this issue?