Hello, We are trying to fit an helix along the Z axis. Are there any libraries that already exist to detect the axis of the helix and to rotate the entire system ? Thanks -- Ph.D. Student Jonathan KHAO LISM-IBSM-CNRS 31 Chemin Joseph Aiguier 13402 Marseille Cedex 20 France jkhao at ibsm.cnrs-mrs.fr tel : 0616738391