Optical Illusion Project

    Imagine two images rolled into one! Consider lines that look curved but are straight, or appear to be different lengths, but are equal. Should you ride the escalator or take the steps that appear to climb and descend at the same time? These are just some examples of optical illusions, images that can be created on a computer screen or artists pallet, that can dazzle the eye, deceive, and often require a second glance.

    Fifth grade Computer Studies students should take some time to explore Internet links (below) and become familiar with examples of optical illusions. The project requires using Logo to re-create an illusion found on the Internet, or create one that is student made. To get credit for the project, students must create a new page in their portfolio called: (initials)optical.htm. Click here to see an example of a completed optical illusion project.

    Make a link from your computer.htm to the Optical Illusion Project. On your optical.htm page, you will need the following:
 

Proper header with title 10 points
Logo illusion 40 points
Procedure text 20 points
Written description 30 points
Total 100 points

    After exploring the Internet examples below, scroll further down this page to learn how to use variables and recursion in Logo.
 

NRICH Logo Archive

This page has some great Logo examples and procedures. Check them out!

The Mathematical Art of M.C. Escher
http://www.mathacademy.com/pr/minitext/escher/

Tessellations, polyhedra, shapes and the logic of space!

Logo Variables and Recursion

    Variables are letters that can take the place of numbers, thus making the value changeable, or variable. Try this procedure:

To Sq  :X                                            Press Enter
Repeat 4[fd :X rt 90]                        use F2 to define

Draw         sq 50          sq 100

    Recursion happens when a procedure repeats itself over and over again. The best optical illusions are often achieved by regulating the recursion so that it does not over-run the graphics screen. The example below uses the term "IF", also known as a conditional:

To Sq  :X
Repeat 4[fd  :x  rt   90]
IF  :X   >  130  [STOP]
Sq  :X  +  10


    To the eye, this image looks like a tunnel, a cone, a pyramid, steps going up or down, or just 13 squares, one on top of the other.

    Using recursion, try substituting the numbers below in the REPEAT statement to work with circles and triangles:
 
 

To CIR  :X
Repeat 36[fd  :X   rt   10]
If  :X  > 10   [STOP]
CIR  :X  + 1		 To TRI  :X
Repeat 3[fd  :X   rt   120]
If   :x   >   120   [STOP]
TRI  :X  +  10

Example of completed project.
 
 
 
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