如何在P5中为球添加弹跳压缩动画？

Question

我用P5.js创建的简单游戏包含一个球，该球受重力作用落下并在地面反弹。我想在球触地时为其添加“压缩”动画，以使其看起来更逼真。我如何做到这一点而又不会显得怪异？代码是这样的：function Ball() {  this.diameter = 50;  this.v_speed = 0;  this.gravity = 0.2;  this.starty = height / 2 - 100;  this.endy = height - this.diameter / 2;  this.ypos = this.starty;  this.xpos = width / 2;  this.update = function() {    this.v_speed = this.v_speed + this.gravity;    this.ypos = this.ypos + this.v_speed;    if (this.ypos >= this.endy) {      this.ypos = this.endy;      this.v_speed *= -1.0; // change direction      this.v_speed = this.v_speed * 0.9;      if (Math.abs(this.v_speed) < 0.5) {        this.ypos = this.starty;      }    }  }  this.show = function() {    ellipse(this.xpos, this.ypos, this.diameter);    fill(255);  }}var ball;function setup() {  createCanvas(600, 600);  ball = new Ball();}function draw() {  background(0);  ball.update();  ball.show();}<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.8.0/p5.js"></script>