Showing papers by "J. Farley Norman published in 1995"

Systematic distortion of perceived three-dimensional structure from motion and binocular stereopsis.

Abstract: The geometric relation between physical and perceived space as specified by binocular stereopsis and structure from motion was investigated. Four experimental tasks were used, each of which required a different aspect of three-dimensional (3-D) structure to be performed accurately. To examine whether the transformation between physical and perceptual space preserved the 3-D structural properties required to perform each of our tasks, the constancy of judged shape over changes in a depicted object's viewing distance or orientation was examined. Our results reveal that observers' judgments of 3-D shape from binocular stereopsis and motion contained systematic distortions: Perceived 3-D shape from motion was not invariant over orientation change and perceived 3-D structure from stereo, and motion and stereo in combination was not invariant over changes in viewing distance.

The perception of surface orientation from multiple sources of optical information

Abstract: One of the fundamental issues in the study of human perception concerns how the shapes of objects in the environment are visually specified from the measurable properties of optical stimulation. There are many different aspects of optical structure that are known to provide perceptually salient information about an object’s threedimensional form. Some of these properties—the socalled pictorial depth cues—are available within individual static images. These include texture gradients, linear perspective, and patterns of shading. Others are defined by the systematic transformations among a sequence of multiple images, and include the disparity between each eye’s view in binocular vision, and the optical deformations that occur when objects are observed in motion. In the theoretical analysis of motion or binocular disparity, two distinct classes of optical phenomena need to be considered. One involves the optical transformations of identifiable image features, such as surface texture or the vertices of a polyhedron, for which it is possible to establish a point-to-point correspondence over multiple views. The ability to match corresponding features in different images is a necessary condition for most existing computational models for the analysis of 3-D shape from motion or stereo, but there are other types of optical transformations that occur frequently in natural vision, for which this condition cannot be satisfied. These include the optical deformations of occlusion contours and smooth gradients of image shading. Patterns of shading in an image arise because of systematic changes in local surface orientation. Patches that are oriented perpendicularly to the prevailing direction of illumination reflect the greatest amount of light, while those that are parallel to the direction of illumination re

The perception of 3-D structure from contradictory optical patterns

Abstract: Two experiments investigated observers’ perceptions of 3-D structure when optical sources of information were contradictory. When motion and stereoscopic disparities specified different surfaces, the perceptual outcome depended strongly on the direction of curvature present within each modality. Previous research has shown that the perception of surface slant and curvature is anisotropic for both motion and stereo and that it depends on the direction in which it takes place. In the present experiments, the modality with the “effective” direction of curvature tended to dominate or suppress the perception of surfaces in the other modality with less effective curvatures. The results have implications for models which attempt to combine 3-D data from different optical sources.