Local Image Features Resulting from 3-Dimensional Geometric Features, Illumination, and Movement: I

Abstract

We study images of smooth or piecewise smooth objects illuminated by a single light source, with only background illumination from other sources. The objects may have geometric features (F), namely surface markings, boundary edges, creases and corners; and shade features (S), namely shade curves and cast shadow curves. We determine the local stable interactions between these and apparent contours (C) for the various configurations of F, S, C, and we concisely summarize them using an "alphabet" of local curve configurations. We further determine the generic transitions for the configurations resulting from viewer movement. These classifications are obtained using the methods of singularity theory, which allows us to ensure that our lists are complete, in some cases correcting earlier attempts at similar classifications.