arcs in 3d?

["Jeffrey A. Edlund" <jaedlund@glaxonlabs.com>]

Hi, 

I'm drawing a figure using epix using arrows in 3d.

arrow(lisa1center,lisa1center-1*lisa1normal); // representing the normal to a triangle in 3d

arrow(lisa1center,lisa1center-(1.0/sqrt(lisa1center|lisa1center))*lisa1center); // arrow pointing towards the origin

I'd like to draw an arc between the 2 arrows an then place a label next
to the arc to indicate the angle.  Is this possible when neither arrow
is in the (x1,x2) plane?

Another simple question:  If I have a P point, how to I access the members of the triple?  i.e. something like point.x point.y point.z?

Thanks, 

Jeffrey