Sunday, February 03, 2008

Scratch: drawing polygons using variables

Information: the turning angle (external angle) for a polygon = 360 / (num of sides)

1) Draw a square

Initially setup so the cat draws a square of 50 steps, starting initially facing upwards

Point in direction 0 (up)

repeat 4
move 50 steps
turn 90 degrees

2) Create two variables: side and angle

Set the angle to 360 / side

Insert the side and angle variables into the polygon procedure as shown:

Use the repeat procedure to draw some different shapes (triangle is shown)

3) Use the Number, Variable and Control blocks to setup a repeat until, as shown:

Now insert the procedure inside the repeat until:

Now draw all the shapes at once, 3 to 8 sides:

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