Programmable Filter: if else statment

[mwestphal (Mathieu Westphal (Kitware))]

Operations on multi-block dataset with Programmable Filter

Ah, indeed. The usual numpy functions do not work for VTKCompositeDataArrays that are available from multiblock datasets, but the numpy-like algorithms provided by vtk.numpy_interface.algorithms do. However, the where function provided in vtk.numpy_interface.algorithms is only the single-argument version, not the three-argument version I suggested, so merging the blocks is the only way to use this numpy expression currently.