Specular Stereo

Abstract

A glossy highlight, viewed stereoscopically, can provide inforrnation about surface shape. For exarnple, highlights appear to lie behind convex surfaces but in front of concave ones . A highlight is a distorted, reflected image of a light source. A ray equation is developed to predict the stereo disparilies generated when a point source of light is reflected in a srnooth, curved surface. This equation can be inverted to infer surface curvature properlies from observed stereo disparilies of the highlighl. To obtain full information about surface curvature in the neighbourhood of the highlight, stereo with two different baselines - or stereo with rnotion parallax - is required. The same ray equation can also be used to predict the monocular appearance of a distributed source. A circular source, for instance, may produce an elliptical specular patch in an image, and the dimensions of the ellipse help to determine surface shape.