Technical Reports

The ICICS/CS Reading Room

UBC CS TR-90-29 Summary

Surface Curvature from Photometric Stereo, October 1990 R. J. Woodham

A method is described to compute the curvature at each point on a visible surface. The idea is to use the intensity values recorded from multiple images obtained from the same viewpoint but under different conditions of illumination. This is the idea of photometric stereo. Previously, photometric stereo has been used to obtain local estimates of surface orientation. Here, an extension to photometric stereo is described in which the spatial derivatives of the intensity values are used to determine the principal curvatures, and associated directions, at each point on a visible surface. The result shows that it is possible to obtain reliable local estimates of both surface orientation and surface curvature without making global smoothness assumptions or requiring prior image segmentation. \n The method is demonstrated using images of several pottery vases. No prior assumption is made about the reflectance characteristics of the objects to be analyzed. Instead, one object of known shape, a solid of revolution, is used for calibration purposes.

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