canvas粒子线条

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JavaScript

window.requestAnimFrame = (function() {
  return (
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function(callback) {
      window.setTimeout(callback);
    }
  );
});

function init(elemid) {
  let canvas = document.getElementById(elemid),
    c = canvas.getContext("2d"),
    w = (canvas.width = window.innerWidth),
    h = (canvas.height = window.innerHeight);
  c.fillStyle = "rgba(30,30,30,1)";
  c.fillRect(0, 0, w, h);
  return {c:c,canvas:canvas};
}

window.onload = function () {
  let c = init("canvas").c,
  canvas = init("canvas").canvas,
  w = canvas.width = window.innerWidth,
  h = canvas.height = window.innerHeight,
  mouse = { x: w / 2, y: h / 2 },
  last_mouse = {};

let n = 2000,
  herd = [];

class point {
    constructor() {
      this.targetIndex = [Math.floor(Math.random() * n)];
      this.f = 10;
      this.ang = Math.random() * 2 * Math.PI;
      this.x = w / 2; //Math.random()*w;
      this.y = h / 2; //Math.random()*h;
      this.ax = this.f * Math.cos(this.ang);
      this.ay = this.f * Math.sin(this.ang);
      this.vx = this.ax;
      this.vy = this.ay;
      this.x += this.vx;
      this.y += this.vy;
      this.nd = Math.random() * 50 + 0.1;
    }
    follow(arr) {
      this.t = { x: 0, y: 0, sumx: 0, sumy: 0 };
      this.count = 0;
      for (let i = 0; i < this.targetIndex.length; i++) {
        this.t.sumx += arr[this.targetIndex[i]].x;
        this.t.sumy += arr[this.targetIndex[i]].y;
        this.count++;
      }
      this.t.x = this.t.sumx / this.count;
      this.t.y = this.t.sumy / this.count;

this.dist = Math.sqrt(Math.pow(this.x - this.t.x, 2) + Math.pow(this.y - this.t.y, 2));
      this.ang = Math.atan2(this.t.y - this.y, this.t.x - this.x);
      this.f = this.dist / 500;

if (this.f < 1) {
        this.f = 1;
      }

if (this.dist > this.nd) {
        this.ax = this.f * Math.cos(this.ang);
        this.ay = this.f * Math.sin(this.ang);
      } else {
        this.ax = this.f * Math.cos(this.ang + Math.PI);
        this.ay = this.f * Math.sin(this.ang + Math.PI);
      }
      this.vx += this.ax;
      this.vy += this.ay;
      this.vx *= 0.9;
      this.vy *= 0.9;
      this.x += this.vx;
      this.y += this.vy;

c.beginPath();
      c.lineTo(this.x, this.y);
      c.lineTo(this.t.x, this.t.y);
      c.strokeStyle = 'white';
      c.lineWidth = 0.1;
      c.stroke();
    }
    show() {
      c.beginPath();
      //c.arc(this.x,this.y,1,0,2*Math.PI);
      c.rect(this.x, this.y, 1, 1);
      c.fillStyle = "white";
      c.fill();
    }}

for (let i = 0; i < n; i++) {
    herd.push(new point());
  }

//initiation

function draw() {
    //animation
    for (let i = 0; i < n; i++) {
      herd[i].follow(herd);
      herd[i].show();
    }
  }

canvas.addEventListener(
  "mousemove",
  function (e) {
    last_mouse.x = mouse.x;
    last_mouse.y = mouse.y;

mouse.x = e.pageX - this.offsetLeft;
    mouse.y = e.pageY - this.offsetTop;
  },
  false);

function loop() {
    window.requestAnimFrame(loop);
    c.fillStyle = "rgba(30,30,30,1)";
    c.fillRect(0, 0, w, h);
    //c.clearRect(0, 0, w, h);
    draw();
  }

window.addEventListener("resize", function () {
    w = canvas.width = window.innerWidth,
    h = canvas.height = window.innerHeight;
    loop();
  });

loop();
  setInterval(loop, 1000 / 60);
};

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