Turtle

Turtle and L-Systems library

L-Systems

The LSystem class is an implementation of the Lindenmayer systems based on an alphabet of symbols and production rules.

const lsystem = new LSystem(axiom, rules);

The axiom is the base sentence from which future sentences will be generated or inferred, and must be composed only by symbols of a defined alphabet. This alphabet is based on the Turtle Graphics movements.

F, G, L, M, D, U, +, -, [, ]

The rules is an array of strings or instances of the Rule class, where each one of them defines a production rule for spawning the next generation sentence.

Generation

The generate method in the LSystem class spawns new generations of the current sentence.

const axiom = 'F';
const rules = [
    'F=>F[+F][-G]'
];
const lsystem = new LSystem(axiom, rules);
console.log(lsystem.sentence); // F
lsystem.generate();
console.log(lsystem.sentence); // F[+F][-G]

This method also admits a number argument that indicates the number of generations to generate.

const axiom = 'F';
const rules = [
    'F=>FG'
];
const lsystem = new LSystem(axiom, rules);
console.log(lsystem.sentence); // F
lsystem.generate(4);
console.log(lsystem.sentence); // FGGGG

Rules

The Rule class represents a production rule that allows the generation from a symbol to a string of one or more symbols from the alphabet.

const str = 'F => F[+F][-F]';
const rules = [ new Rule(str) ];
console.log(rule.base); // F
console.log(rule.next); // ['F', '[', '+', 'F', ']', '[', '-', 'F', ']']

The LSystem class uses this class to maintain and generate the sentences.

Turtle Graphics

The Turtle class is a clumsy attempt to use a "sentence" driven drawing engine based on the turtle graphics. The sentences use the same symbols in the LSystem and Rule alphabet, with each symbol having a specific usage.

Symbol | Action --------| ------ F, G| Advances forward a certain amount of steps drawing a line M | Advances forward a certain amount of steps without drawing a line L | Draws a tree leaf U | Upscale drawing (divides current scale by scale ratio, with initial scale is 1) D | Downscale drawing (multiplies current scale by scale ratio, with initial scale is 1) + | Turn right a certain angle - | Turn left a certain angle [ | Saves current context ] | Restores current context

The render method reads each symbol in the string, and performs an action according to the previous table.

const turtle = new Turtle(config);
turtle.render(sentence);

Turtle Config

The config argument for the Turtle class constructor has these properties:

Property | Type | Description -------------|----------------------------|------------ context | CanvasRenderingContext2D | Canvas rendering context used for drawing strokeSize | number | Lenght of each step used stroke or move (may be affected by scaling) strokeWeight | number | Width of the stroke (may be affected by scaling) angle | number | Angle used for each turn (+ and -) scale | ScaleConfig | Scale config

The ScaleConfig has this properties:

Property | Type | Description ------------------|-----------|------------ ratio | number | Scale ratio (between 0 and 1) to be applied when upscaling or downscaling scaleStrokeSize | boolean | Optional (default false), specifies if the stroke length must be scaled scaleStrokeWeight | boolean | Optional (default false), specifies if the stroke weight must be scaled scaleAngle | boolean | Optional (default false), specifies if the angle must be scaled