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Shaw Gillespie, Myron Braunstein, George Andersen; The perception of path curvature: Effects of projected velocity and projected size. Journal of Vision 2008;8(6):22. doi: 10.1167/8.6.22.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research (Todd, 1984) has shown that observers can judge 3-D surface curvature from the motion of texture elements in a 2-D projection. Our recent research (VSS, 2007) found that observers are sensitive to available velocity information when judging the trajectory of an object moving along a straight path in a 3-D scene. The present study examines the degree to which the projected velocity function and the projected size change function can be used to judge the sign of curvature of the motion trajectory of an object moving towards the observer. The displays simulated a ball moving towards the observer above the ground against a realistic scene background. The simulated motion path was either curved upward or downward relative to a level path, with one of two curvature magnitudes in each direction. The projected path was identical in all conditions. In one condition, the curvature of the simulated path was indicated by both the projected size change function and the projected velocity function. In a second condition, the curvature was indicated only by the size change function, with the velocity function corresponding to a level path. In the third condition, the velocity function indicated the curvature, with the size change function indicating a level path. Observers were able to judge the direction of curvature (upward or downward) from the velocity change function alone, but not from the size change function alone. This indicates that variations in projected velocity indicating path curvature are more important than variations in projected size in determining perceived curvature in a 3-D scene.
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