Motion parallax is a monocular depth cue arising from the relative velocities of objects moving across the retinae of a moving person. The term parallax refers to a change in position. Thus, motion parallax is a change in position caused by the movement of the viewer. Motion parallax arises from the motion of the observer in the environment. It is perhaps easier to think of what motion parallax is by imagining yourself as a passenger in a car looking out the side window. The car is moving very fast down the highway. The objects very close to the window, such as the small trees planted by the highway, seem to rush by. Beyond the small trees, you can see a distant farmhouse. The farmhouse appears to move more slowly relative to you in the car. You know that the trees and the farmhouse are standing still; you are the object that is moving. You can observe this phenomenon in the video below. This video shows clouds moving by a plane. The closer the cloud to the plane, the faster it appears to move.
In this activity, you can see how motion parallax arises. Object that are farther away move move slowly across the retina as we move by them. Use this activity to observe how this gemometric relationship leads to motion parallax.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
Below is a list of the ways that you can alter the illustration. The settings include the following:
Animate: Moves they eye from the top of the screen to the bottom, and repeats.
This creates the motion necessary to show how motion parallax occurs.
Object to Track: Chose to have they just look at the opposite side to stay fixated on one of the objects.
Eye Position: When the animation is not moving, you can move the eye up and down along the side at your own pace.
You can also move the eye by clicking and dragging on the screen with a mouse or by touching the screen.
Pressing this button restores the settings to their default values.