Examples of current projects
How the perceptual
horizon affects 3D motion perception
The perceived layout of objects and
the relation between the judged size and judged distance of objects in a 3D scene
depends on the position of the objects relative to the perceptual horizon. The location of the perceptual horizon is
determined by both the implied vanishing point in a scene and the location at
which the visible surface terminates. We
are currently studying the effect of the location of the perceptual horizon on
the perceived trajectory of moving objects.
Observers view scenes in which an object moves against a linear
perspective line drawing background or a real scene background. The location of perceptual horizon is varied
by changing the height of the implied vanishing point and the height at which
the visible ground surface terminates.
An object moves 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 are asked to judge
whether object has changed its motion path in 3D or traveled along a straight
path. The level of the implied vanishing
point has a significant effect on the perception of a change in the motion
path, whereas the height at which the surface terminates does not. However, the height at which the surface
terminates interacts 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. (Ozkan & Braunstein, 2008
Vision Sciences Society Meeting)
Judging the path of an object moving
in a 3D scene
Observers have been shown to be
sensitive to available velocity information when judging the trajectory of an
object moving along a straight path in a 3D scene. Our current research
examines the degree to which the projected velocity function and the projected
size change function can be used to judge the curvature of the motion path of
an object moving towards the observer. The displays simulate a ball moving
towards the observer above the ground against a realistic scene background. The
simulated motion path is either curved upward or downward relative to a level
path, with one of two curvature magnitudes in each direction. The projected path is identical in all
conditions. In one condition, the
curvature of the simulated path is indicated by both the projected size change
function and the projected velocity function. In a second condition, the
curvature is indicated only by the size change function, with the velocity
function corresponding to a level path.
In the third condition, the velocity function indicates the curvature,
with the size change function indicating a level path. Observers are 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 3D scene. (Gillespie, Braunstein & Andersen, 2008 Vision Sciences Society Meeting)
Research supported by NIH grant EY18334 to George J. Andersen, University of California, Riverside
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