Surface shapes are then deduced from the distortions of the patterns that are produced on Object's Surface. Knowing relevant camera and projector geometry, depth can be inferred by triangulation. Many methods have been developed using this approach. The essence of the method is that a grating is projected onto an object and an image is formed in the plane of some reference grating as shown in Fig. 6 . The image then interferes with the reference grating to form Moire fringe contour patterns which appear as dark and light stripes, as demonstrated by Fig. 7 .
Ambiguities arise in interrogating the fringe patterns.
It is not possible to determine whether adjacent contours are higher or lower in depth. Resolve by moving one of the gratings and taking multiple Moire images. Reference grating can also be omitted and its effect can be simulated in software. Methods are relatively computationally expensive. Shape from Shading Methods Methods based on shape from shading employ photometric stereo techniques to produce depth measurements.