-- Zero out velocity in a particular direction.
stopAxis :: V3 Float -> Camera -> Camera
stopAxis axis (Camera r t v u) = flip (Camera r t) u $ 
                                 v ^-^ dot (rotate r axis) v *^ axis
stopAxis :: V3 Float -> Camera -> Camera
stopAxis axis (Camera r t v u) = flip (Camera r t) u $ 
                                 v ^-^ dot (rotate r axis) v *^ axis
stopAxis axis (Camera r t v u) = flip (Camera r t) u $ 
                                 v ^-^ dot (rotate r axis) v *^ axis