L-Systems

The concept

An L-system (Lindenmayer, 1968) is a formal grammar: an axiom (initial string) and rewriting rules. After N iterations, the resulting string is interpreted graphically: F = move forward, + = turn left, - = turn right, [ = save, ] = restore. This produces realistic plant forms.

The code

// L-system tree
let sentence = 'F', rules = {'F':'FF+[+F-F-F]-[-F+F+F]'};
function setup() {
  createCanvas(400, 280); background(11,15,20);
  for (let i = 0; i < 4; i++) {
    let next = '';
    for (let c of sentence) next += rules[c] || c;
    sentence = next;
  }
  translate(width/2, height); stroke(55,227,195); strokeWeight(1);
  for (let c of sentence) {
    if (c==='F') { line(0,0,0,-4); translate(0,-4); }
    else if (c==='+') rotate(radians(22));
    else if (c==='-') rotate(radians(-22));
    else if (c==='[') push();
    else if (c===']') pop();
  }
  noLoop();
}

Going further

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