INTEGRATION OF SHADING AND TEXTURE CUES - TESTING THE LINEAR-MODEL

One of the first attempts to develop a formal model of depth cue integ ration is to be found in Maloney and Landy's [(1989) Proceedings of th e SPIE: Visual communications and image processing, Part 2 (pp. 1154-1 163)] ''human depth combination rule''. They advocate that the combina tion of depth cues by the visual system is best described by a weighte d linear model. The present experiments tested whether the linear comb ination rule applies to the integration of texture and shading. As wou ld be predicted by a linear combination rule, the weight assigned to t he shading cue did not vary as a function of its curvature value. Howe ver, the weight assigned to the texture cue varied systematically as a function of the curvature values of both cues. Here we describe a non -linear model which provides a better fit to the data. Redescribing th e stimuli in terms of depth rather than curvature reduced the goodness of fit for all models tested. These results support the hypothesis th at the locus of cue integration is a curvature map, rather than a dept h map. We conclude that the linear combination rule does not generaliz e to the integration of shading and texture, and that for these cues i t is likely that integration occurs after the recovery of surface curv ature.