← Notebooks/Turtles – showcase🏝️ 4/4 cells interactive

Turtle art!

This notebook recreates some famous works of art with simple turtle code — and every drawing is a WasmMakie.jl figure, so the interactive ones recompute right in your browser via WebAssembly.

using WasmMakie, PlutoUI

turtle_drawing_fast (generic function with 1 method)

"The Starry Night"

Vincent van Gogh (1889)

draw_star (generic function with 1 method)

function draw_star(turtle, points, size)
	for i in 1:points
		right!(turtle, 360 / points)
		forward!(turtle, size)
		backward!(turtle, size)
	end
end

"Tableau I"

Piet Mondriaan (1913)

draw_mondriaan (generic function with 1 method)

"Een Boom"

Luka van der Plas (2020)

# Built inline (a plain `let`, NOT a `do` closure): the L-system is written
# ITERATIVELY with an explicit work-stack of (x, y, heading, depth), so we never
# mutate-and-restore turtle fields across recursive calls — and we don't pass a
# bond-capturing closure that allocates a stack to `turtle_drawing_fast`, both of
# which WasmTarget can't yet compile. Same strokes + same render as the others.
fractal = let
	t = Turtle()
	penup!(t)
	backward!(t, 15)
	pendown!(t)
	stack = NTuple{4,Float64}[(t.pos[1], t.pos[2], t.heading, 0.0)]
	while !isempty(stack)
		st = pop!(stack)
		x = st[1]; y = st[2]; h = st[3]; depth = st[4]
		depth >= 10.0 && continue
		size = fractal_base * 0.5 ^ (depth * 0.5)
		t.pos = (x, y)
		t.heading = h
		color_hsl!(t, depth * 30.0, 0.8, 0.5)
		forward!(t, size * 8.0)
		nx = t.pos[1]; ny = t.pos[2]
		push!(stack, (nx, ny, h + fractal_tilt / 2.0, depth + 1.0))
		push!(stack, (nx, ny, h + fractal_tilt / 2.0 - fractal_angle, depth + 1.0))
	end
	# same figure render as `turtle_drawing` (white background → no backdrop span)
	fig = Figure(size = (320, 320))
	ax = Axis(fig[1, 1])
	hidedecorations!(ax)
	hidespines!(ax)
	ax.xmin = -15.0; ax.xmax = 15.0
	ax.ymin = -15.0; ax.ymax = 15.0
	for k in 1:length(t.xs)
		lines!(ax, t.xs[k], t.ys[k]; color = t.cols[k], linewidth = 1.5)
	end
	fig
end

lindenmayer (generic function with 1 method)

"Een coole spiraal"

fonsi (2020)

@bind angle Slider(0:90; default=20)

turtle_drawing() do t

	let i = 0.0
		while i <= 10.0
			right!(t, angle)
			forward!(t, i)
			i += 0.1
		end
	end

end

rand_choice! (generic function with 1 method)

# A tiny deterministic PRNG (xorshift64*) — pure Julia, so the random art
# recomputes identically inside the wasm islands. Seeded by the buttons.
begin
	mutable struct ArtRNG
		state::UInt64
	end
	ArtRNG(seed::Integer) = ArtRNG(UInt64(seed + 1) * 0x9e3779b97f4a7c15 + 0x2545f4914f6cdd1d)

	function nextfloat!(r::ArtRNG)
		s = r.state
		s ⊻= s << 13
		s ⊻= s >> 7
		s ⊻= s << 17
		r.state = s
		Float64(s >> 11) / 9.007199254740992e15   # [0, 1)
	end
	rand_between!(r::ArtRNG, lo, hi) = Float64(lo) + nextfloat!(r) * (Float64(hi) - Float64(lo))
	rand_choice!(r::ArtRNG, xs) = xs[1 + Int(floor(nextfloat!(r) * length(xs)))]
end