• Background
  • Instructions
  • Illustration
  • Quiz


Now imagine you are driving a car on a winding country road. The motion cues for depth are a combination of optic flow, relative movement coming directly at you, and motion parallax, relative movement at a 90° angle from you. Add in hills for up-and-down motion, and even more depth cues become available. The amazing thing about our visual system is that it computes all these relative distances and speeds fast enough for us to make sense of the world, even at 65 mph.

Use this activity to explore how optic flow works.


Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab

On the Illustration tab, you can start, stop and alter the motion of squares to experience optic flow.


Below is a list of the ways that you can alter the illustration. The settings include the following:

Move/Stop: Starts or stops demonstration.
Change Direction: Causes squares to change from moving out to moving in or vice versa.
Center: Returns the motion to centering on the animation area.
Speed : Changes the speed of animation.
Clicking or touching the animation area : The animation will move to the point you click or touch and will expand or shrink into this point.


Pressing this button restores the settings to their default values.