javascript - 阻止重力作用下的弹跳球消失

Question

我想模拟一个球的弹跳，并在将来创建更多球并使它们反弹。这是我的代码(使用 p5.js，一个 JavaScript 处理库)

var xpos = 200;
var ypos = 450;
var vy = 0;
var gravity = 0.6;
var bounce = -1.00;
var diameter = 30;

function setup() {
    var myCanvas = createCanvas(windowWidth, windowHeight);

    stroke(255);
    noFill();
}

function draw() {
    background(0);

  ellipse(xpos, ypos, diameter, diameter);

  vy += gravity;
  ypos += vy;

  if(ypos > (windowHeight - diameter/2)) {
    vy *= bounce;
  }

}

看起来好像工作正常，但是当弹跳非常小时，它开始出现故障并消失，here's a codepen 。我不知道如何让它停止并滚动或其他什么(如果没有 x 属性，显然不会滚动，但只是在弹跳停止后停止移动)

感谢任何帮助，谢谢。

Answer 1

您想要首先应用加速度，然后进行碰撞测试，然后调整碰撞位置。

如果您想要恢复原状，请在每次碰撞后将其应用于 vy，例如

编辑:还使用检查来查看对象是否应该“休息”有帮助

var xpos = 200;
var ypos = 0;
var vy = 0;
var gravity = 10;
var bounce = 0.9;  // typically represented as a positive normalized value
var diameter = 30;
var sleepTolerance = gravity;  // this will provide a solid result

// KA variables
var windowHeight = height;
var windowWidth = width;

frameRate(30);
var draw = function() {
    background(0);

    ellipse(xpos, ypos, diameter, diameter);

    var asleep = false;

    if(!asleep){
        vy += gravity;
        ypos += vy;
    }

    var heightAboveGround = ypos - (windowHeight - diameter/2);
    if(heightAboveGround > 0) { // remember y is inverted
        // position adjusted for reflection after collision
        // including restitution (resulting from the bounce)
        ypos -= bounce * heightAboveGround;

        // apply restitution to subsequent velocity
        vy *= -bounce;

        if (heightAboveGround <= sleepTolerance && abs(vy) <= sleepTolerance){
            asleep = true;
            ypos = windowHeight - diameter/2;
        }
    }
};