Moire contouring methods have been shown to be able to delineate the full surfaces of gently curved parts. One limitation of most interferometric based methods is that the resulting fringe pattern does not differentiate between positive and negative slope surfaces (peaks from valleys). Many dynamic analysis methods, such as phase shifting, do permit slope determination through the use of multiple images. This paper presents a method of moire fringe generation which discriminates peaks from valleys through the use of phase gratings. A phase grating creates a change in a static moire pattern whenever the sign of the surface slope changes. By selecting the sign of one slope on a continuous surface, the sign of any other region can be determined. The slopes are determined by the phase of the moire fringe pattern without moving the fringes. This method does not provide absolute slope determination, but only relative to any other slope on the same, continuous surface. We discuss the basic theory of moire fringe generation using phase gratings, and relate the fringe creation mechanism to an explanation of the slope effect. Finally, we present experimental results of some simple examples of practical applications of this method.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.