fractal-tree.pde

void setup() {
  size(800, 600);
  background(255);

  stroke(119, 117, 173);
  drawTree(width/2, height, 100, 0, 12);

  save("fractal-tree.png");

  println("done!");
}

/**
 * rootX 枝のx座標
 * rootY 枝のy座標
 * len 枝の長さ
 * stand 枝の方向から枝の傾き
 * n 残りの再帰回数
 **/
void drawTree(float rootX, float rootY, float len, float stand, int n) {
  final float scale = 0.85; // 枝が短くなる比率
  final float angle = 15; // 枝の広がり

  float rootX2 = rootX + len * sin(radians(stand));
  float rootY2 = rootY - len * cos(radians(stand));

  stroke(round(119 + (1-rootY2/height) * (255 - 119)), 
    round(117 + (1-rootY2/height) * (255 - 117)), 
    round(173 + (1-rootY2/height) * (255 - 173)));

  line(rootX, rootY, rootX2, rootY2);

  if (n >= 1) {
    drawTree(rootX2, rootY2, len*scale, stand - angle, n-1);
    drawTree(rootX2, rootY2, len*scale, stand + angle, n-1);
  }
}