The spiral is rotating around the z-axis, which is pointing out from the screen. Change the angles beta and gamma to tilt the other two axes. Change the parameter 'a' to get different versions of the spiral!
A ship that maintains a constant compass direction, will sail along a loxodrome. Pedro Nunes, Mercator and Escher http://cvc.instituto-camoes.pt/ciencia_eng/e6.html Wolfram Mathworld - Spherical Spiral: http://mathworld.wolfram.com/SphericalSpiral.html
