Sorry, I forgot to mention that the code samle for the Worker class was inspired from here: http://www.comp.nus.edu.sg/~cs3249/lecture/multithreading.pdf <http://www.comp.nus.edu.sg/~cs3249/lecture/multithreading.pdf> -- Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html