trialex: When you hold a cup in front of you, aren't you able to pour on two axis, i.e. left and right or towards and away from you?
I guess so! I tried picking up my cup, and yeah I guess you can pour forward/back left/right, but when I went to do it pratically I poured in any place by moving my whole arm then twisting my wrist inwards. Twiting it outwards felt un-natural and I think you wouldn't have the same strength in that direction.
Anyways that probably doesn't help you if you are trying to determine where someone is puring based on the puring action alone. Sounds like an interesting project though - good luck!