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Systematic distortions of shape from stereopsis
1University Laboratory of Physiology, Oxford, U.K.
Vision Research
|January 1, 1991
Summary
Perception of 3-D shape from stereograms is distorted by viewing distance. Horizontal disparity scaling with incorrect egocentric distance causes these shape illusions, affecting 3-D shape perception.
Area of Science:
- Visual perception
- Computational neuroscience
- Psychophysics
Background:
- Stereoscopic vision relies on horizontal disparities to perceive depth and shape.
- The perceived 3-D shape of objects can be influenced by viewing distance and egocentric distance estimations.
Purpose of the Study:
- To investigate how disparity information defines 3-D shape perception of curved surfaces.
- To determine the impact of viewing distance on the perceived shape of cylinders presented in stereograms.
Main Methods:
- Subjects judged the shape of cylindrical surfaces presented as random dot stereograms.
- Stimuli were viewed at close, intermediate, and far distances.
- Indirect measures of egocentric distance scaling were calculated from shape judgments.
Main Results:
- Cylinders appeared elongated at close distances and flattened at far distances.
- Perception was near veridical at intermediate viewing distances.
- Shape distortions correlated with viewing distance, suggesting egocentric distance miscalibrations.
Conclusions:
- The study indicates that perceived 3-D shape is susceptible to distortions based on viewing distance.
- Incorrect scaling of horizontal disparities with egocentric distance is a primary cause of these shape distortions.
- Findings highlight the complex interplay between disparity, distance perception, and 3-D shape representation in the visual system.