"Zoom" is a little tricky. For perspective cameras, zoom corresponds
to the field-of-view, which must be greater than 0 and less than 180
degrees. For orthographic cameras, zoom corresponds to changing the
width/height of the projection, which must be greater than zero and
less than infinity. Coming up with a UI that works for both finite (0
to 180) and infinite ranges is a little annoying.
If you implement stereo viewing, you need to do slightly different
things for ortho and perspective. Etc.
You're right, all of this isn't really that big a deal, and it seems
that enough people want orthographic cameras that the extra work is
> I suggest replacing the height-angle with a screen height & width.
What units are the screen height and width in? Pixels? (NOoooooo..)
World coordinates at the near clipping plane? Far clipping plane?
Inventor's model seems to work pretty well...