canvas线条旋转动画

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JavaScript

"use strict";

class Vector {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }

add(v) {
    return new Vector(
      this.x + v.x,
      this.y + v.y);
  }

addTo(v) {
    this.x += v.x;
    this.y += v.y;
  }

sub(v) {
    return new Vector(
      this.x - v.x,
      this.y - v.y);
  }
  
  subFrom(v) {
    this.x -= v.x;
    this.y -= v.y;
  }
  
  mult(n) {
    return new Vector(this.x * n, this.y * n);
  }
  
  multTo(n) {
    this.x *= n;
    this.y *= n;
    return this;
  }
  
  div(n) {
    return new Vector(this.x / n, this.y / n);
  }
  
  setAngle(angle) {
    var length = this.getLength();
    this.x = Math.cos(angle) * length;
    this.y = Math.sin(angle) * length;
  }
  
  setLength(length) {
    var angle = this.getAngle();
    this.x = Math.cos(angle) * length;
    this.y = Math.sin(angle) * length;
  }
  
  getAngle() {
    return Math.atan2(this.y, this.x);
  }
  
  getLength() {
    return Math.sqrt(this.x * this.x + this.y * this.y);
  }

getLengthSq() {
    return this.x * this.x + this.y * this.y;
  }

distanceTo(v) {
    return this.sub(v).getLength();
  }

copy() {
    return new Vector(this.x, this.y);
  }
  
  equals(v) {
    return this.x == v.x && this.y == v.y;
  }
}

let canvas;
let ctx;
let w, h;
let size;
let circles;

class Circle {
  constructor(r) {
    this.r = r;
    let nrOfPoints = 24;
    this.points = [];
    for (let circlePoint = 0; circlePoint < nrOfPoints; circlePoint++) {
      let angle = Math.PI * 2 / nrOfPoints * circlePoint;
      let x = Math.cos(angle) * r;
      let y = Math.sin(angle) * r;
      this.points.push(new Vector(x, y));
    }
  }

move() {
    let deltaAngle = 0.05 * this.r / size;
    this.points.forEach(p => {
      let x2 = Math.cos(deltaAngle) * p.x - Math.sin(deltaAngle) * p.y;
      let y2 = Math.sin(deltaAngle) * p.x + Math.cos(deltaAngle) * p.y;
      p.x = x2;
      p.y = y2;
    });
  }}

class Circles {
  constructor(nrOfCircles) {
    this.init(nrOfCircles);
  }

init(nrOfCircles) {
    this.circles = new Array(nrOfCircles);
    let s = size / nrOfCircles * 0.45;
    for (let i = 0; i < nrOfCircles; i++) {
      let r = i * s + s;
      this.circles[i] = new Circle(r);
    }
  }

move() {
    this.circles.forEach(c => c.move());
  }

draw() {
    for (let circle = 0; circle < this.circles.length - 1; circle++) {
      let nrOfPoints = Math.min(this.circles[circle].points.length, this.circles[circle + 1].points.length);
      for (let i = 0; i < nrOfPoints; i++) {
        ctx.beginPath();
        ctx.moveTo(this.circles[circle].points[i].x, this.circles[circle].points[i].y);
        ctx.lineTo(this.circles[circle + 1].points[i].x, this.circles[circle + 1].points[i].y);
        ctx.stroke();
        ctx.beginPath();
        ctx.arc(this.circles[circle].points[i].x, this.circles[circle].points[i].y, 3, 0, Math.PI * 2);
        ctx.fill();
        ctx.beginPath();
        ctx.arc(this.circles[circle + 1].points[i].x, this.circles[circle + 1].points[i].y, 3, 0, Math.PI * 2);
        ctx.fill();
      }
    }
  }}

function setup() {
  canvas = document.querySelector("#canvas");
  ctx = canvas.getContext("2d");
  reset();
  window.addEventListener("resize", reset);
}

function reset() {
  w = canvas.width = window.innerWidth;
  h = canvas.height = window.innerHeight;
  size = Math.min(w, h);
  ctx.translate(w / 2, h / 2);
  setupCircles();
}

function setupCircles() {
  circles = new Circles(5);
}

function draw() {
  requestAnimationFrame(draw);
  ctx.clearRect(-w / 2, -h / 2, w, h);
  circles.draw();
  circles.move();
}

setup();
draw();

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