Shape perception in different settings

How an object appears depends on geometrical and physical properties of its surface. Moreover, objects occur in an environment and the context in which objects are embedded affects the perception of their shapes. In this paper the influences of scene geometry and viewing conditions on shape perception are investigated in a systematic way. Stimuli are actual 3D scenes. The objects in the scenes are triaxial ellipsoids placed on a turntable, in a controlled lightfield, and against a distant backdrop. The ellipsoids approximate Lambertian diffuse reflection (finished matte white). Visual shape is measured by probing local surface attitude: a 'gauge figure' has to be adjusted such that it appears as a circle painted upon the surface of the objects. Form and orientation of this gauge figure can be translated into slant and tilt values at the sampled locations. Scene geometry is varied parametrically. Detailed quantitative results of the effects of scene geometry have been gathered by manipulating size, distance and orientation of the objects relative to the observer. Depending on context overestimation of relief by a factor of 2 - 4 occurs. Slant overestimations are less for larger objects and more distant objects.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.