1. In mission editor, place any soldier unit as player.
2. In player units init line:
foo = [] spawn {while {true} do {sleep 1; hintSilent format ["player vectorUp\n%1", vectorUp player]}}
3. Preview mission.
4. Move around, find a cross sloped surface to deploy on.
5. Go prone.
6. Align view across the slope (left of screen is directly downhill, right is directly uphill or other way around).
7. Deploy weapon. Rotate view left or right (uphill or downhill) to the limit. Undeploy weapon.
8. Repeat steps 6 and 8, notice vectorUp gets further from vertical each time.