1. A method comprising: observing, by a projection-vision system implemented by one or more processors configured with executable instructions, a finger shadow by a projection-vision system, as the finger shadow appears on an interactive surface; computing at least one shadow image by the projection-vision system based on the observing the finger shadow; and determining, by the projection-vision system, whether the at least one finger is touching or hovering over the interactive surface based on an analysis of the at least one shadow image.