1. A process for controlling positioning of an implement relative to a workpiece, which comprises: projecting a light pattern including an array of light elements, each having a known shape and spacing relative to one another, on the workpiece, sensing the array of light elements as reflected from the workpiece, clustering the sensed light elements into groups based on at least one common characteristic resulting from workpiece geometry of the light elements as reflected, defining a plurality of surfaces of the workpiece geometry by fitting a mathematical surface to at least some of the clustered groups of sensed light elements, defining the workpiece geometry from at least some of the defined surfaces, and controlling the positioning of the implement and the workpiece relative to one another based on the so-defined workpiece geometry.