Abstract
We reported previously (VSS, 2007) that the perceived layout of objects and the relation between the judged size and judged distance of objects in a 3-D scene depends on the position of the objects relative to the perceptual horizon. We found that the perceptual horizon was determined by a weighted combination of the implied vanishing point and the termination of the visible surface texture. The present study examined the effect of the location of the perceptual horizon on the perception of an object's motion trajectory. Observers viewed scenes in which an elliptical object moved against a linear perspective background. The location of the perceptual horizon was varied by changing the height of the implied vanishing point and the height of the texture boundary. The object moved with a constant projected speed to a constant height along one of three linear motion paths: diagonal from lower left to upper right, diagonal from lower right to upper left or vertical from bottom to top. Observers were asked to judge whether the object had changed its motion path in 3D or traveled along a straight path. We found that the level of the implied vanishing point had a significant effect on the perception of a change in the motion path whereas the height of the visible surface texture did not have a significant main effect on observers' judgments. However, the height of the texture boundary interacted with the level of the implied vanishing point in determining observers' perception of the motion trajectories. These results suggest that the perceived trajectories of objects in a scene depend on the location of the perceptual horizon which is affected both by the implied vanishing point and by the height at which the ground surface terminates.
Supported by NIH grant EY18334.