An apparatus determines a cursor position in an illumination field of a projector. An obstruction is detected in the illumination field. The cursor position is determined as the point on the obstruction furthest from where the obstruction crosses a border of the illumination field. A distance to the point on the obstruction is determined and compared to a distance to a point not on the obstruction. Gestures are recognized as a function of movement of the obstruction and the determined distances.