Scared animals instinctively know to stay perfectly still, especially those species that wear camouflage on their skin or fur. Think of an arctic hare hiding in the snow from wolves or polar bears. Its white fur allows it to blend in perfectly with the winter snow. However, keeping still is also critical to an animal or a person attempting to hide via camouflage. Once prey is in motion, predators can detect the motion, despite the camouflage. Indeed, we demonstrate in this section that we are often able to detect form directly from the perception of motion when motion cues are the only cues to what an object is.
In this activity, the camouflage will be extrene, a random pattern of black and white dots against a background of random black and white dots. By making the dots move, the small square is easily seen. You can also alter how the dots in either the background or the small square can be updated as the square moves.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
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:
Dot Update: What dots change if any during the motion of the square.
The options are:
Static: None of the dots change during motion.
Square Dynamic: The dots of the small square change randomly during motion.
All Dynamic: All dots change during motion.
Background Dynamic: The dots of the background change randomly during motion.
Move: Start and stop the motion of the small square.
Size of Dots: Make the dots bigger and larger. The dots are always double size if the background is changing (All Dynamic or Background Dynamic).
Center: Redraw the small square in the center of the screen.
Pressing this button restores the settings to their default values.