NetLogo Models Library:
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Optical Illusions

Run Optical Illusions in your browser uses NetLogo 5.0.1 requires Java 5 or higher (system requirements) Note: If you download the NetLogo application, every model in the Models Library (besides the Community Models) is included. If you have trouble running this model in your browser, you may wish to download the application instead.

## WHAT IS IT?

This model presents six optical illusions.

## HOW IT WORKS

The optical illusions are constructed using a combination of NetLogo turtles and patches.

### Illusion #1

White circles on a gray background produce an illusion of the circles changing colors between black and white, depending on where you focus your eyes.

### Illusion #2

Diagonals moving away from the center create an illusion of depth, which makes the parallel horizontal lines seem to bend in the center.

### Illusion #3

The perpendicular lines that do not match row to row create an illusion of the lines between them being not parallel.

### Illusion #4

Relative sizes of other circles skew the perception of the middle circles, creating an illusion of difference in size.

### Illusion #5

Circles of diamonds seem to rotate as you focus your eyes on their center.

### Illusion #6

Intensely saturated colors create an illusion of rippling waves of motion.

## HOW TO USE IT

Press a button to choose an illusion, and it will be presented in the NetLogo view.

Some explanatory text will appear in the monitor below the view.

## EXTENDING THE MODEL

Add more illusions.

## NETLOGO FEATURES

Many of the illusions in the model, such as illusions 2, 4 and 5, involve turtles positioned in a circle around a middle point. This shows how to use `forward` and `heading` to position objects in a pattern.

## RELATED MODELS

Other models that were created "for fun" include Frogger, Lunar Lander and other games included in the Games section of the Models Library.

## CREDITS AND REFERENCES

Illusion #6 is based on the cover of the album "Merriweather Post Pavilion" by Animal Collective, which in turn is based on an illusion by Akiyoshi Kitaoka.

## HOW TO CITE

If you mention this model in a publication, we ask that you include these citations for the model itself and for the NetLogo software:
- Wilensky, U. (2005). NetLogo Optical Illusions model. http://ccl.northwestern.edu/netlogo/models/OpticalIllusions. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
- Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

## COPYRIGHT AND LICENSE

Copyright 2005 Uri Wilensky.


This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.

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