On Sun, 18 May 2003 03:24:54 -0500, Marc Jacquier wrote:


> But pov  uses a left hand coordinate system: x-right, y-up, z -ahead
>
>

You're right, of course (as are other replies to my post, thanks!), but
the radial coordinates should be independent of the cartesian ones. That
is, theta is defined as the angle from the positive vertical axis whether
you name that axis "y" or "z" or "Jean-Pierre".

However, it is the function f_ph which returns this value.  I was just
curious why it was defined that way, and thought that perhaps the
definitions of phi and theta were not exactly universal--much like the
question of y-up v. z-up or right-handed v. left-handed  cartesian coordinate
systems.  (Again, I could call it "phi" or "theta" or "Franz" and it
woudld be the same thing...)

Anyway, it's not really important so long as you know what's coming out of
the functions.  Thanks, everyone, for your replies.

	-Ed

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