For a number of years, observations have been made of contour-like patterns created by the moiré interference of a grid with its shadow cast onto a surface. The conditions under which these patterns correspond to planar contours are derived, and systems to generate these contours are suggested. It is shown that moiré contour patterns provide a useful and flexible means of contouring surfaces. Experimental results are presented.
D. M. Meadows, W.O Johnson, and J. B. Allen, "Generation of Surface Contours by Moiré Patterns," Appl. Opt. 9, 942-947 (1970)