External zfp?
-DVTK_USE_EXTERNAL=ON
does not set -DVTK_MODULE_USE_EXTERNAL_VTK_zfp=ON
, which is not a recognized variable anyway. Even setting directly -DVTK_MODULE_USE_EXTERNAL_vtkzfp=ON
seems without any effect. I guess this is because https://gitlab.kitware.com/vtk/vtk/-/blob/master/ThirdParty/zfp/CMakeLists.txt has the _internal
suffix, but not sure why this is that way.