Get-Turtle
Turtle Graphics in PowerShell
Turtle Graphics in PowerShell. Draw any image with turtles in a powershell.
Turtle Graphics are pretty groovy.
They have been kicking it since 1966, and they are how computers first learned to draw.
They kicked off the first computer-aided design boom and inspired generations.
They are also incredibly easy to build.
A Turtle graphic is described with a series of moves.
Let's start with the core three moves:
Imagine you are a Turtle holding a pen.
- You can turn
rotate - You can move
forward - You can lift the pen
These are the three basic moves a turtle can make.
We can describe more complex moves by combining these steps.
As a PowerShell turtle, we can take any pipeline of objects and turn them into turtles.
Each argument can be the name of a method or property of the turtle object.
After a member name is encountered, subsequent arguments will be passed to the member as parameters.
We can write shapes as a series of steps. Let's start with a simple diagonal line
turtle rotate 45 forward 42
Let's draw an equilateral triangle
turtle forward 42 rotate 120 forward 42 rotate 120 forward 42
Typing that might get tedious. Instead, let's use a method. Polygon will draw an an N-sided polygon.
turtle polygon 10 5
There's also a method for squares
turtle square 42
If we rotate 45 degrees first, our square becomes a rhombus
turtle rotate 45 square 42
We can also draw a rectangle
turtle rectangle 42 4.2
If we only provide the first parameter, we get a golden rectangle
turtle rectangle 42
Circles
We can draw a circle
turtle circle 10
Or a pair of half-circles
turtle circle 10 0.5 rotate 90 circle 10 0.5
We can multiply arrays in PowerShell this can make composing complex shapes easier. Let's take the previous example and repeat it 8 times.
turtle @('circle',42,0.5,'rotate',90 * 8)
Let's make a triangle by multiplying steps
turtle ('forward', 10, 'rotate', 120 * 3)
We can also write this with a polygon
turtle polygon 10 3
Let's make a series of polygons, decreasing in size
turtle polygon 10 6 polygon 10 5 polygon 10 4
We can also use a loop to produce a series of steps Let's extend our previous example and make 9 polygons
turtle @(
foreach ($n in 12..3) {
'polygon'
42
$n
}
)
We can use the same trick to make successively larger polygons
turtle @(
$sideCount = 3..8 | Get-Random
foreach ($n in 1..5) {
'polygon'
$n * 10
$sideCount
}
)
We can reflect a shape by drawing it with a negative number
turtle polygon 42 3 polygon -42 3
We can change the angle of reflection by rotating first
turtle rotate 60 polygon 42 3 polygon -42 3
We can morph any N shapes with the same number of points.
turtle square 42 morph @(
turtle square 42
turtle rotate 45 square 42
turtle square 42
)
Reflections always have the same number of points.
Morphing a shape into its reflection will zoom out, flip, and zoom back in.
turtle polygon 42 6 morph @(
turtle polygon -42 6
turtle polygon 42 6
turtle polygon -42 6
)
If we want to morph a smaller shape into a bigger shape,
we can duplicate lines
turtle polygon 21 6 morph @(
turtle @('forward', 21,'backward', 21 * 3)
turtle polygon 21 6
turtle @('forward', 21,'backward', 21 * 3)
)
We can repeat steps by multiplying arrays. Lets repeat a hexagon three times with a rotation
turtle ('polygon', 23, 6, 'rotate', -120 * 3)
Let's change the angle a bit and see how they overlap
turtle ('polygon', 23, 6, 'rotate', -60 * 6)
Let's do the same thing, but with a smaller angle
turtle ('polygon', 23, 6, 'rotate', -40 * 9)
Flowers
A flower is a series of repeated polygons and rotations
turtle Flower
Flowers look pretty with any number of polygons
turtle Flower 50 10 (3..12 | Get-Random) 36
Flowers get less dense as we increase the angle and decrease the repetitions
turtle Flower 50 15 (3..12 | Get-Random) 24
Flowers get more dense as we decrease the angle and increase the repetitions.
turtle Flower 50 5 (3..12 | Get-Random) 72
Flowers look especially beautiful as they morph
$sideCount = (3..12 | Get-Random)
turtle Flower 50 15 $sideCount 36 morph @(
turtle Flower 50 10 $sideCount 72
turtle rotate (
Get-Random -Max 360 -Min -360
) Flower 50 5 $sideCount 72
turtle Flower 50 10 $sideCount 72
)
Petals and Flowers
We can draw a pair of arcs and turn back after each one.
We call this a 'petal'.
turtle rotate -30 Petal 42 60
We can construct a flower out of petals
turtle FlowerPetal
Adjusting the angle of the petal makes our petal wider or thinner
turtle FlowerPetal 42 15 (20..60 | Get-Random) 24
Flower Petals get more dense as we decrease the angle and increase repetitions
turtle FlowerPetal 42 10 (10..50 | Get-Random) 36
Flower Petals get less dense as we increase the angle and decrease repetitions
turtle FlowerPetal 50 20 (20..72 | Get-Random) 18
Flower Petals look amazing when morphed
$Radius = 23..42 | Get-Random
$flowerAngle = 30..60 | Get-Random
$AngleFactor = 2..6 | Get-Random
$StepCount = 36
$flowerPetals =
turtle rotate (
(Get-Random -Max 180) * -1
) flowerPetal $radius 10 $flowerAngle $stepCount
$flowerPetals2 =
turtle rotate (
(Get-Random -Max 180)
) flowerPetal $radius (
10 * $AngleFactor
) $flowerAngle $stepCount
turtle flowerPetal $radius 10 $flowerAngle $stepCount morph (
$flowerPetals,
$flowerPetals2,
$flowerPetals
)
Arcs and Suns
We can arc right or left
turtle arcRight 42 120
turtle arcLeft 42 120
We can arc right and then left to produce a ray or wave shape
turtle arcRight 42 120 arcLeft 42 120
We can rotate and repeat that rays to make a sun
$Length = 42
$Angle = 160
$RayAngle = 90
$StepCount = 9
turtle sun $Length $Angle $RayAngle $StepCount
If we reverse the ray angle and morph, the sun really shines!
turtle Sun 100 135 60 8 morph @(
turtle Sun 100 135 60 8
turtle Sun 100 135 -60 8
turtle Sun 100 135 60 8
)
We can add multiple fixed colors to make a gradient Then the sun is truly bright.
turtle Sun 100 135 60 8 fill 'yellow' 'goldenrod' stroke 'goldenrod' 'yellow' morph @(
turtle Sun 100 135 60 8
turtle Sun 100 135 -60 8
turtle Sun 100 135 60 8
)
Stars
We can create a Star with N points
turtle star 42 5
turtle star 42 6
turtle star 42 7
turtle star 42 8
Stars look spectacular when we rotate and repeat them
turtle @('star',42,5,'rotate',72 * 5)
turtle @('star',42,6,'rotate',60 * 6)
turtle @('star',42,7,'rotate',(360/7) * 7)
turtle @('star',42,8,'rotate',45 * 8)
Starflowers
When we do this, we call it a Star Flower
turtle StarFlower 42
turtle StarFlower 42 30 6 12
turtle StarFlower 42 (360/7) 7 7
turtle StarFlower 42 45 8 8
StarFlowers look spectacular when morphed
turtle StarFlower 42 45 8 24 morph @(
turtle StarFlower 42 45 8 24
turtle StarFlower 42 15 8 24
turtle StarFlower 42 45 8 24
)
We can rotate the points we morph into.
turtle StarFlower 42 45 8 24 morph @(
turtle StarFlower 42 45 8 24
turtle rotate (Get-Random -Max 360) StarFlower 42 15 8 24
turtle StarFlower 42 45 8 24
)
We can mix the number of points in a star flower morph
(as long as we're drawing the same number of points)
turtle StarFlower 42 12 5 30 morph @(
turtle StarFlower 42 12 5 30
turtle rotate (
Get-Random -Max 360 -Min -360
) StarFlower 42 14.4 6 25
turtle StarFlower 42 12 5 30
)
Scissors
We can construct a 'scissor' by drawing two lines at an angle
turtle Scissor 42 60
Drawing a scissor does not change the heading
We can create a zig-zag pattern by multiplying scissors
turtle @('Scissor',42,60 * 4)
Getting a bit more interesting, we can create a polygon out of scissors
We will continually rotate until we have turned a multiple of 360 degrees.
Turtle ScissorPoly 23 90 120
Turtle ScissorPoly 23 60 72
This can get very chaotic, if it takes a while to reach a multiple of 360
Let's build a dozen scissor polygons.
foreach ($n in 60..72) {
Turtle ScissorPoly 16 $n $n
}
Step Spirals
We can draw an outward spiral by growing a bit each step
turtle StepSpiral
turtle StepSpiral 42 120 4 18
Because Step Spirals are a fixed number of steps,
they are easy to morph.
turtle StepSpiral 42 120 4 18 morph @(
turtle StepSpiral 42 90 4 24
turtle StepSpiral 42 120 4 24
turtle StepSpiral 42 90 4 24
)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
Step spirals look lovely when morphed
(especially when reversing angles)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6) morph @(
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
turtle @('StepSpiral',6, -120, 'rotate',120 * 6)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
)
When we reverse the spiral angle, the step spiral curve flips
turtle @('StepSpiral',3, 90, 'rotate',90 * 4) morph @(
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
turtle @('StepSpiral',3, -90, 'rotate',90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
)
When we reverse the rotation, the step spiral curve slides
turtle @('StepSpiral',3, 90, 'rotate',90 * 4) morph @(
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',-90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
)
We we alternate, it looks amazing
turtle @('StepSpiral',3, 90, 'rotate',90 * 4) morph @(
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',-90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
turtle @('StepSpiral',3, -90, 'rotate',90 * 4)
turtle @('StepSpiral',3, 90, 'rotate',90 * 4)
)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6) morph @(
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
turtle @('StepSpiral',6, -120, 'rotate',120 * 6)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
turtle @('StepSpiral',6, 120, 'rotate',-120 * 6)
turtle @('StepSpiral',3, 120, 'rotate',60 * 6)
)
Spirolaterals
turtle spirolateral
turtle spirolateral 50 60 10
turtle spirolateral 50 120 6 @(1,3)
turtle spirolateral 23 144 8
turtle spirolateral 23 72 8
Bezier Curves
We can draw simple Bezier Curves. Imagine a string being tugged by a point
turtle bezierCurve 0 100 100 100
A morph can help us understand bezier curve movement
turtle bezierCurve 0 100 100 100 morph @(
turtle bezierCurve 0 100 100 100
turtle bezierCurve 100 0 100 100
turtle bezierCurve 0 100 100 100
)
Lets make it more exaggerated
turtle viewbox 150 bezierCurve 0 100 100 100 morph @(
turtle bezierCurve 0 200 100 100
turtle bezierCurve 200 0 100 100
turtle bezierCurve 0 200 100 100
)
We use the shorthand 's' for a simple bezier curve
turtle s 100 0 100 100
This helps make beautifully short moprhs
turtle s 100 0 100 100 morph @(
turtle s 100 0 100 100
turtle s 0 100 100 100
turtle s 100 0 100 100
)
We can also draw quadratic bezier curves
turtle quadraticbezierCurve 0 100 100 100
We can use the alias q, and morph them, too.
turtle q 0 100 100 100 morph @(
turtle q 100 0 100 100
turtle q 0 100 100 100
turtle q 100 0 100 100
)
We can also draw cubic bezier curves For these, imaging a string being pulled by two other strings.
turtle cubicBezierCurve 0 100 100 0 100 100
We can shorten this to c, and morph it in beautiful ways
turtle width 200 height 200 morph @(
turtle c 0 0 0 0 200 200
turtle c 0 200 200 0 200 200
turtle c 0 0 0 0 200 200
turtle c 200 0 0 200 200 200
turtle c 0 0 0 0 200 200
)
turtle width 200 height 200 start 200 200 morph @(
turtle c 0 0 0 0 -200 200
turtle c 0 200 -200 0 -200 200
turtle c 0 0 0 0 -200 200
turtle c -200 0 0 200 -200 200
turtle c 0 0 0 0 -200 200
)
We can start at a given location, and morph along an axis.
turtle width 200 height 200 morph @(
turtle start 100 0 c 0 0 0 0 0 200
turtle start 100 0 c -100 0 100 200 0 200
turtle start 100 0 c 0 0 0 0 0 200
)
turtle width 200 height 200 morph @(
turtle start 0 100 c 0 0 0 0 200 0
turtle start 0 100 c 0 -100 200 100 200 0
turtle start 0 100 c 0 0 0 0 200 0
)
Bar Graphs
Lets get practical. Turtle can easily make a bar graph.
turtle BarGraph 200 300 (1..10)
Want a vertical bar graph? Rotate first.
turtle rotate 90 BarGraph 200 300 (1..10)
Let's provide more random points:
turtle rotate 90 BarGraph 200 300 (1..20 | Get-Random -Count 20)
We can draw pretty pictures by connecting and rotating graphs
turtle @(
'BarGraph', 200, 300, (1..10),
'BarGraph', 200, 300, (10..1),
'rotate',180 * 2
)
Pie Graphs
Want a Piece of Pie?
Turtle Pie 100 4
Turtle Pie 100 6
Turtle Pie 100 8
Want a quarter?
Turtle Pie 100 (1/4)
How about a range of slices?
Turtle Pie 100 (1..10)
What about some colorful slices?
Turtle Pie 100 @(
foreach ($color in 'red', 'green', 'blue') {
@{
Value = 1
PathClass = "$color-fill foreground-stroke"
Fill = $color
Title = $color
}
}
)
What about some random colorful slices?
Turtle Pie 100 @(
foreach ($color in 'red', 'green', 'blue', 'yellow', 'magenta','cyan') {
@{
Value = (Get-Random -Max 100)
PathClass = "$color-fill foreground-stroke"
Fill = $color
Title = $color
}
}
)
Circle Arcs
Pie graphs are made out of circle arcs
Turtle id Quadrants @(
'CircleArc',42, 90,
'Rotate', 90 * 4
)
Turtle id Sextants @(
'CircleArc',42, 60,
'Rotate', 60 * 6
)
Turtle id Octants @(
'CircleArc',42, 45,
'Rotate', 45 * 8
)
We can alternate rotations and arcs to create radial stripes
Turtle 'Rotate', -22.5 @(
'Rotate', 15,
'CircleArc',42, 15,
'Rotate', 15 * 24
)
Turtle 'Rotate', -15 @(
'Rotate', 30,
'CircleArc',42, 30,
'Rotate', 30 * 12
)
Turtle @(
'Rotate', 60,
'CircleArc',42, 60,
'Rotate', 60 * 6
)
We can draw negative circle arcs
Turtle CircleArc 42 -90
Negative quadrants
Turtle @(
'CircleArc',42, -90,
'Rotate', 90 * 4
)
Negative sextants
Turtle @(
'CircleArc',42, -60,
'Rotate', 60 * 6
)
Negative octants
Turtle @(
'CircleArc',42, -45,
'Rotate', 45 * 8
)
We can combine arcs and movement to make a pinwheel
turtle @(
'circlearc', 42, 60,
'rotate',60,
'forward',42 * 6
)
Lets morph positive quadrants into negative quadrants
$quadrants = Turtle @(
'CircleArc',42, 90,
'Rotate', 90 * 4
)
$quadrants | turtle morph @(
$quadrants
Turtle @(
'CircleArc',42, -90,
'Rotate', 90 * 4
)
$quadrants
)
Lets morph positive sextants into negative sextants
$sextants = Turtle id Sextants @(
'CircleArc',42, 60,
'Rotate', 60 * 6
)
$sextants | turtle morph @(
$sextants
Turtle @(
'CircleArc',42, -60,
'Rotate', 60 * 6
)
$sextants
)
Lets morph positive octants into negative octants
$octants = Turtle id Octants @(
'CircleArc',42, 45,
'Rotate', 45 * 8
)
$octants | turtle morph @(
$octants
Turtle @(
'CircleArc',42, -45,
'Rotate', 45 * 8
)
$octants
)
We can overlap pinwheels to make even more exotic shapes
turtle @(
@(
'circlearc', 21, -60,
'rotate',60,
'forward',42 * 6
'rotate', 30
) * 12
)
We can morph and spin these exotic shapes to create hypnotic animations
$exoticShape = turtle (
@(
'circlearc', 21, -60,
'rotate',60,
'forward',42 * 6
'rotate', 30
) * 12
)
$exoticShape |
turtle morph @(
$exoticShape
turtle (
@(
'circlearc', 21, 60,
'rotate',60,
'forward',42 * 6
'rotate', 30
) * 12
)
$exoticShape
) pathAnimation @{
type = 'rotate'
values = 0, 360
repeatCount = 'indefinite'
}
Turtles all the way down
Turtles can contain turtles. Let's make a circle inscribed into a square
turtle viewbox 42 turtles ([Ordered]@{
'square' = turtle square 42
'circle' = turtle circle 21
})
Each turtle can have a distinct color or CSS class
turtle viewbox 42 turtles ([Ordered]@{
'square' = turtle square 42 pathclass 'blue-fill foreground-stroke'
'circle' = turtle circle 21 pathclass 'cyan-fill foreground-stroke'
})
Lets make some colorful boxes
turtle viewbox 42 turtles @([Ordered]@{
'q1' = turtle start 0 0 square 21 pathclass 'red-fill foreground-stroke'
'q2' = turtle start 21 0 square 21 pathclass 'green-fill foreground-stroke'
'q3' = turtle start 21 21 square 21 pathclass 'yellow-fill foreground-stroke'
'q4' = turtle start 0 21 square 21 pathclass 'blue-fill foreground-stroke'
})
Nested turtles can morph! Let's move these squares around.
turtle viewbox 42 turtles @([Ordered]@{
'q1' = turtle viewbox 21 fill red pathclass 'red-fill foreground-stroke' morph @(
turtle start 0 0 square 21
turtle start 21 0 square 21
turtle start 21 21 square 21
turtle start 0 21 square 21
turtle start 0 0 square 21
)
'q2' = turtle viewbox 21 fill green pathclass 'green-fill foreground-stroke' morph @(
turtle start 21 0 square 21
turtle start 21 21 square 21
turtle start 0 21 square 21
turtle start 0 0 square 21
turtle start 21 0 square 21
)
'q3' = turtle viewbox 21 fill yellow pathclass 'yellow-fill foreground-stroke' morph @(
turtle start 21 21 square 21
turtle start 0 21 square 21
turtle start 0 0 square 21
turtle start 21 0 square 21
turtle start 21 21 square 21
)
'q4' = turtle viewbox 21 fill blue pathclass 'blue-fill foreground-stroke' morph @(
turtle start 0 21 square 21
turtle start 0 0 square 21
turtle start 21 0 square 21
turtle start 21 21 square 21
turtle start 0 21 square 21
)
})
Let's make a colorful cubic morph
$Colors = @('fill', '#4488ff','stroke','#224488','pathclass', 'brightBlue-fill','blue-stroke')
turtle width 200 height 200 turtles @(
turtle morph @(
turtle c 0 0 0 0 200 200
turtle c 0 200 200 0 200 200
turtle c 0 0 0 0 200 200
turtle c 200 0 0 200 200 200
turtle c 0 0 0 0 200 200
) @colors
turtle morph @(
turtle c 0 0 0 0 -200 200
turtle c 0 200 -200 0 -200 200
turtle c 0 0 0 0 -200 200
turtle c -200 0 0 200 -200 200
turtle c 0 0 0 0 -200 200
) @colors
turtle morph @(
turtle teleport 100 0 c 0 0 0 0 0 200
turtle teleport 100 0 c -100 0 100 200 0 200
turtle teleport 100 0 c 0 0 0 0 0 200
) @colors
turtle morph @(
turtle teleport 0 100 c 0 0 0 0 200 0
turtle teleport 0 100 c 0 -100 200 100 200 0
turtle teleport 0 100 c 0 0 0 0 200 0
) @colors
)
Webs
Turtle can draw webs
Turtle Spiderweb
Turtle can draw spiderwebs with any number of spokes and rings
Turtle Spiderweb 7 13
Turtle Spiderweb 7 13
We can draw random webs
$spokes = Get-Random -Min 3 -Max 13
$rings = Get-Random -Min 3 -Max (13 * 3)
turtle web 42 $spokes $rings morph @(
turtle web 42 $spokes $rings
turtle rotate (
Get-Random -Max 360
) web 42 $spokes $rings
turtle web 42 $spokes $rings
) stroke 'goldenrod' pathclass 'yellow-stroke'
We can draw a web with color and class
Turtle Spiderweb 7 13 stroke goldenrod pathclass 'yellow-stroke'
We can draw a random web with color and class
$spokes = Get-Random -Min 5 -Max 13
$rings = Get-Random -Min 3 -Max (13 * 3)
turtle web 42 $spokes $rings morph @(
turtle web 42 $spokes $rings
turtle rotate (
Get-Random -Min 90 -Max 360
) web 42 $spokes $rings
turtle web 42 $spokes $rings
) stroke goldenrod pathclass 'yellow-stroke'
L-Systems
Turtle can draw a number of fractals
turtle BoxFractal 42 4
We can make a Board Fractal
turtle BoardFractal 42 4
We can make a Crystal Fractal
turtle CrystalFractal 42 4
We can make ring fractals
turtle RingFractal 42 4
We can make a Pentaplexity
turtle Pentaplexity 42 3
We can make a Triplexity
turtle Triplexity 42 4
We can draw the Koch Island
turtle KochIsland 42 4
Or we can draw the Koch Curve
turtle KochCurve 42
We can make a Koch Snowflake
turtle KochSnowflake 42
We can draw the Levy Curve
turtle LevyCurve 42 6
We can use a Hilbert Curve to fill a space
Turtle HilbertCurve 42 4
We can use a Moore Curve to fill a space with a bit more density.
turtle MooreCurve 42 4
We can rotate and repeat moore curves, giving us even Moore.
turtle @('MooreCurve', 42, 4, 'Rotate', 90 * 4)
We can show a binary tree
turtle BinaryTree 42 4
We can make fractal plants
turtle FractalPlant 42 4
We can also make fractal shrubs
turtle FractalShrub 42 4
The SierpinskiArrowHead Curve is pretty
turtle SierpinskiArrowheadCurve 42 4
The SierpinskiTriangle is a Fractal classic
turtle SierpinskiTriangle 42 4
We can morph with no parameters to try to draw step by step
This will result in large files, and may not work in all browsers
For best results, adjust the precision
turtle SierpinskiTriangle 42 3 morph
Let's draw two reflected Sierpinski Triangles
turtle @(
'rotate', 60
'SierpinskiTriangle', 42, 4
'SierpinskiTriangle', -42, 4
)
Now let's draw a dozen reflected Sierpinski Triangles
turtle @(
'rotate', 60,
'SierpinskiTriangle', 42, 4,
'SierpinskiTriangle', -42, 4,
'rotate', 30 *
12
)
We can draw a 'Sierpinski Snowflake' with multiple Sierpinski Triangles.
turtle @('rotate', 30, 'SierpinskiTriangle',42,4 * 12)
turtle @('rotate', 45, 'SierpinskiTriangle',42,4 * 24)