shithub: graphical-algorithms

ref: f5f4fb16ed24308c78ba1fdc5e84cbcaba53c51c
dir: /marching-squares/

#!/bin/slug

-- Implementation of the marching squares algorithm
-- see https://en.wikipedia.org/wiki/Marching_squares

ROWS = 100
COLS = 100
mt = {}

function b(a, b, c, d)
	return a*8 + b*4 + c*2 + d
end

function setup()
	size(1000, 1000)
	background(235)
	stroke(0)
	strokeWeight(1)
	for y = 1, ROWS+1 do
		mt[y] = {}
		for x = 1, COLS+1 do
			v = 0
			if math.random() >= 0.5 then v = 1 end
			mt[y][x] = v
		end
	end

	cx = width / ROWS
	cy = height / COLS
	for y = 0, ROWS-1 do
		for x = 0, COLS-1 do
			n = b(mt[y+1][x+1], mt[y+1][x+2], mt[y+2][x+2], mt[y+2][x+1])
			if n == 1 then
				line(x*cx, (y+0.5)*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 2 then
				line((x+1)*cx, (y+0.5)*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 3 then
				line(x*cx, (y+0.5)*cy, (x+1)*cx, (y+0.5)*cy)
			elseif n == 4 then
				line((x+0.5)*cx, (y+0)*cy, (x+1)*cx, (y+0.5)*cy)
			elseif n == 5 then
				line((x)*cx, (y+0.5)*cy, (x+0.5)*cx, (y)*cy)
				line((x+0.5)*cx, (y+1)*cy, (x+1)*cx, (y+0.5)*cy)
			elseif n == 6 then
				line((x+0.5)*cx, y*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 7 then
				line(x*cx, (y+0.5)*cy, (x+0.5)*cx, y*cy)
			elseif n == 8 then
				line(x*cx, (y+0.5)*cy, (x+0.5)*cx, y*cy)
			elseif n == 9 then
				line((x+0.5)*cx, y*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 10 then
				line((x+0.5)*cx, (y+0)*cy, (x+1)*cx, (y+0.5)*cy)
				line(x*cx, (y+0.5)*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 11 then
				line((x+0.5)*cx, (y+0)*cy, (x+1)*cx, (y+0.5)*cy)
			elseif n == 12 then
				line(x*cx, (y+0.5)*cy, (x+1)*cx, (y+0.5)*cy)
			elseif n == 13 then
				line((x+1)*cx, (y+0.5)*cy, (x+0.5)*cx, (y+1)*cy)
			elseif n == 14 then
				line(x*cx, (y+0.5)*cy, (x+0.5)*cx, (y+1)*cy)
			end
		end
	end
end

function draw()
	noLoop()
end