作っていて「これはちょっと…」と思えたアニメーション。
人によっては不快感を感じるかもしれない、ある意味人間臭い動きのアルゴリズム。

画像をクリックするとアニメーションサイトに遷移します。

let angle;
let angleOffset;
let trees = [];

function setup() {
  createCanvas(windowWidth,windowHeight);
  colorMode(HSB, 250, 100, 100);
  background(0);
  angleMode(DEGREES);
  noFill();
  angle = 10;
  angleOffset = 400;

  const treeCount = 10; // Change this value to control the number of trees
  for (let i = 0; i < treeCount; i++) {
    trees.push(new Tree());
  }
}

function draw() {
  background(0);

  for (const tree of trees) {
    tree.update();
    tree.show();
  }
}

class Tree {
  constructor() {
    this.x = random(width);
    this.y = random(height / 2, height);
    this.length = random(50, 100);
    this.tx = random(10000);
    this.ty = random(10000);
    this.tl = random(10000);
    this.speedX = random(0.021, 0.01);
    this.speedY = random(0.051, 0.01);
    this.speedL = random(0.501, 0.01);
  }

  update() {
    this.x = map(noise(this.tx), 0, 1, 0, width);
    this.y = map(noise(this.ty), 0, 1, height / 2, height);
    this.length = map(noise(this.tl), 0, 1, 50, 100);
    this.tx += this.speedX;
    this.ty += this.speedY;
    this.tl += this.speedL;
  }

  show() {
    push();
    translate(this.x, this.y);
    scale(2); // <-- Adjust this value to control the size of the tree
    let depth = 0;
    drawBranch(this.length, depth);
    pop();
  }
}


function drawTree(x, y, length) {
  push();
  translate(x, y);
  let depth = 0;
  drawBranch(length, depth);
  pop();
}

function drawBranch(length, depth) {
  let hue = map(noise(frameCount * 0.01, depth * 0.1), 0, 1, 0, 360);
  stroke(hue, 100, 100);
  strokeWeight(map(depth, 0, 10, 5, 1));

  if (length > 10) {
    line(0, 0, 0, -length);
    translate(0, -length);

    let leftAngle = angle + map(noise(frameCount * 0.01, depth * 0.1), 0, 1, -angleOffset, angleOffset);
    let rightAngle = angle + map(noise(frameCount * 0.01, depth * 0.1 + 5), 0, 1, -angleOffset, angleOffset);

    push();
    rotate(leftAngle);
    drawBranch(length * 0.67, depth + 1);
    pop();

    push();
    rotate(-rightAngle);
    drawBranch(length * 0.67, depth + 1);
    pop();
  } else {
    line(0, 0, 0, -length);
  }
}

function windowResized(){
  resizeCanvas(windowWidth, windowHeight);
}