Hi Amibt,
do not know if you already made it or are any longer interested in a 3Dpointer. I'm stuck at the very same point than you seem to be.
With the vec_for_screen function I get the x coordinate mapped alright (moving the mouse my model-entity moves from right to left border of the view). Moving the mouse up and down moves the entity forwards and backwards - but not to the borders of the view (it stops before reaching the end or goes beyond it).
The z-axis (up and down movement of the entity) I do with two keys. Will do it with the mouse-wheel in a while. All that works fine except for the up down movement of the mouse.
So if someone has some ideas about that I would be thankful.

Moreover, has anybody got some clarifying drawings of how the axis are arranged (coordinate-system) in A5. Would be nice to show them somewhere because that would greatly improve the imagination of what happens with all that vector stuff...

Ok bye for now.