Locomotion- plus additional reading (highlighted with an asterisk*)
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Course
Active Vision
Institution
Cardiff University (CF)
Book
Active Vision
This lecture summary was based on how we guide our own self-movement- what cues does one use to get to a target?
The lecture explores two hypotheses: optic flow and egocentric direction. The lecture explores the role of extra retinal signals, models of heading, and fascinating phenomenons such as ...
Lecture 6:
Locomotion:
*Lappe et al (1999)- accurate and efficient control of self-motion is an
important requirement for daily behaviour. Visual feedback about self-motion is
provided by optic flow. Optic flow can be used to estimate the direction of self-
motion (‘heading’) rapidly and efficiently.
Optic flow is the pattern of motion at the retina that specifies the direction of
locomotion (Warren, 2001).
What visual information do you use to guide walking to a target?
Gibson (1947)- how do we select the best
people to be pilots? Need to know how do
you fly a plane, if you know how to fly a
plane then you can test those specific skills.
Nobody knew back then, so Gibson started
thinking about that problem.
The cartoon representation of a pilot flying
a plane show that the plane is going to hit
the run way in the centre as the arrows that
indicate motion within in the image are
showing the focus of expansion. The focus
of expansion tells you where you are going
to go. “The centre of the flow pattern during forward movement of the animal is
the direction of movement...To aim locomotion at an object is to keep the centre
of flow of the optic array as close as possible to the form which the object
projects.” Can tell where you are going by looking at the focus of expansion, and if
you're not going where you want to be going you can change it.
Certain patterns of moton can be used to suggest which directon you're moving in.
There are three different types of movement; forward, moving sideways and moving
eye with things at different distances. Optc fow is the pattern of apparent moton of
objects, surfaces and edges in a visual scene caused by the relatve moton between
the observer and a scene (Burton & Radford, 1978).
Two hypotheses (Warren, 2001):
1. Optc fow: the observer moves so the cancel the error between the heading
perceived from optc fow and the goal, placing the FoE on the target. Subsequent
fow provides informaton about the adequacy of the steering adjustment.
2. Egocentric directon: the observer perceives the visual directon of the goal with
respect to the body, and walks in that directon. Can be accomplished by centering
the goal at the midline and moving forward.
Warren & Hannon (1988): If you use optc fow, you should be able to
judge where you're going only on the basis of optc fow. Used
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