Not only is the angle of importance, but also the direction from which
you view the angle.
I'd venture to say the keyword is "projection", as what the OP is
looking for is a projection of an angle in 3d to a 2d plane.
These are my personal views and not those of Fujitsu Siemens Computers!
Josef Mlers (Pinguinpfleger bei FSC)
If failure had no penalty success would not be a prize (T. Pratchett)
Company Details: http://www.yqcomputer.com/