A numerical controller accepts an instruction for the cutting of pockets with perimeters of irregular shapes, the instruction defining the perimeter by a series of vertex points and a straight-line, circular, or some other interpolation to move between these vertices. The numerical controller cuts the perimeter of the pocket by reference to the vertex points and constructs a bit map indicating the cut and uncut material after completion of the perimeter. A rule-based path generator employs the bit map to complete the interior of the pocket without explicit programming of those interior tool motions. The bit map is constructed on a real-time basis by offsetting the tool motion coordinates to roll over in the bit map space regardless of the tool starting position.