- optical illusions
Set of 3 illusions using radiating or concentric lines to distort a shape or figure.
Orbinson Illusion:
To
New
# set default screen, pen and turtle values
ResetAll SetScreenSize [400 400] HideTurtle
SetSC Black SetPC Green SetPS 1 PenUp
End
To
Square
:
Side
# square (side x side) drawn from centre (tp)
Back
:
Side
/2 Right 90 Back
:
Side
/2 PenDown
Repeat 4 [
Forward
:
Side
Left 90]
PenUp Forward
:
Side
/2 Left 90 Forward
:
Side
/2
# r2c
End
To
Go
New
SetPC Red SetPW 3
SetPos [0 -70]
Square
200
SetPos [0 275] SetH 204 SetPW 1 SetPC Yellow PenDown
Repeat 17 [Forward 510 Back 510 Left 3]
End
Hering Figure:
To
New
# set default screen, pen and turtle values
ResetAll SetScreenSize [400 400] HideTurtle
SetSC Black SetPC Green SetPS 1 PenUp
End
To
Go
New
SetPC Yellow PenDown
Repeat 2 [
Left 20 Repeat 29 [Forward 300 Back 300 Left 5]
Left 15]
SetPC Red SetPW 3
PenUp SetPos [-60 -200] PenDown Forward 400
PenUp SetPos [60 -200] PenDown Forward 400
End
Ehrenstein Illusion:
To
New
# set default screen, pen and turtle values
ResetAll SetScreenSize [400 400] HideTurtle
SetSC Black SetPC Green SetPS 1 PenUp
End
To
Square
:
Side
# square (side x side) drawn from centre (tp)
Back
:
Side
/2 Right 90 Back
:
Side
/2 PenDown
Repeat 4 [
Forward
:
Side
Left 90]
PenUp Forward
:
Side
/2 Left 90 Forward
:
Side
/2
# r2c
End
To
Go
New
SetPC Yellow
For [Radius 55 190 15] [
Circle
:
Radius
]
SetPW 3 SetPC Red Right 45
Square
240
End