A simple L-System implementation in JavaScript.

An L-System is a way of generating self similar fractals using a set of simple commands and production rules. By replacing each symbol of the initial seed using these production rules it is possible construct very complex geometric structures after just a few iterations.

Rendering of the generated tree is done using Turtle Graphics. The commands supported are:

+ Anticlockwise rotation.

- Clockwise rotation.

[ Push to stack (Save current position and angle).

] Pop from stack (Restore saved position and angle).

F Draw forward.

	var canvas = document.getElementById('canvas');

	var plant = Lindenmayer.createLSystem({
		seed: 'X',
		rules: {
			'X': 'F-[[X]+X]+F[+FX]-X',
			'F': 'FF'
		},
		canvas: canvas,
		angle: 22.5
	});
    
	plant.iterate(8);
    
	plant.render();
    

This will render an L-System that fills the entire canvas. X is the starting seed of the system. The rules object lists the production rules used to expand the tree each iteration. angle is used when rendering and dictates the amount the rotation commands will alter the drawing direction.

	var canvas = document.getElementById('canvas');

	var sierpinskiTriangle = Lindenmayer.createLSystem({
		seed: 'A',
		rules: {
			'A': 'B-A-B',
			'B': 'A+B+A'
		},
		canvas: canvas,
		angle: 60,
		constants: ['A', 'B'],
		initialAngle: 90,
		x: 100,
		y: 200,
		width: 512,
		height: 512,
		color: '#0000ff'
	});
	
	sierpinskiTriangle.iterate(9);

	sierpinskiTriangle.render();
    

F is the default drawing command. By adding constants it is possible to use others as well, in this case A and B. initialAngle is the starting direction of the L-System. x, y, width and height should be self explanatory as well as color.