This link seems to have very helpful information:

http://www.heavens-above.com/constellation.aspx?lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT

A script to plot Right ascention and Declination, and even spot size for magnitude, translating from Ra, Dec, with spherical coordinates,
to x,y,z might help?

- Brian

Source of above information, and more: http://www.astronomyforum.net/amateur-astronomy-forum/32911-drawing-constellations.html

(http://www.rtgui.com/ links to Cartes du Ciel)