为什么我的球消失了？

Question

请原谅这个有趣的头衔.我已经创建了一个200个球弹跳和碰撞的小图形演示,两个都在墙壁和彼此之间.您可以在此处查看我目前所拥有的内容:http://www.exeneva.com/html5/multipleBallsBouncingAndColliding/

问题是,每当它们相互碰撞时,它们就会消失.我不知道为什么.有人可以看看并帮助我吗？

更新:显然球阵列有坐标为NaN的球.下面是我将球推到阵列的代码.我不完全确定坐标是如何获得NaN的.

// Variables
var numBalls = 200;  // number of balls
var maxSize = 15;
var minSize = 5;
var maxSpeed = maxSize + 5;
var balls = new Array();
var tempBall;
var tempX;
var tempY;
var tempSpeed;
var tempAngle;
var tempRadius;
var tempRadians;
var tempVelocityX;
var tempVelocityY;

// Find spots to place each ball so none start on top of each other
for (var i = 0; i < numBalls; i += 1) {
  tempRadius = 5;
  var placeOK = false;
  while (!placeOK) {
    tempX = tempRadius * 3 + (Math.floor(Math.random() * theCanvas.width) - tempRadius * 3);
    tempY = tempRadius * 3 + (Math.floor(Math.random() * theCanvas.height) - tempRadius * 3);
    tempSpeed = 4;
    tempAngle = Math.floor(Math.random() * 360);
    tempRadians = tempAngle * Math.PI/180;
    tempVelocityX = Math.cos(tempRadians) * tempSpeed;
    tempVelocityY = Math.sin(tempRadians) * tempSpeed;

    tempBall = {
      x: tempX, 
      y: tempY, 
      nextX: tempX, 
      nextY: tempY, 
      radius: tempRadius, 
      speed: tempSpeed,
      angle: tempAngle,
      velocityX: tempVelocityX,
      velocityY: tempVelocityY,
      mass: tempRadius
    };
    placeOK = canStartHere(tempBall);
  }
  balls.push(tempBall);
}

Answer 1

您的错误最初来自此行:

var direction1 = Math.atan2(ball1.velocitY, ball1.velocityX);

你有ball1.velocitY(而undefined不是)ball1.velocityY.所以Math.atan2给你NaN,这个NaN价值在你所有的计算中传播.

这不是您的错误的来源,但您可能希望在这四行中更改其他内容:

ball1.nextX = (ball1.nextX += ball1.velocityX);
ball1.nextY = (ball1.nextY += ball1.velocityY);
ball2.nextX = (ball2.nextX += ball2.velocityX);
ball2.nextY = (ball2.nextY += ball2.velocityY);

您不需要额外的任务,只需+=单独使用运算符:

ball1.nextX += ball1.velocityX;
ball1.nextY += ball1.velocityY;
ball2.nextX += ball2.velocityX;
ball2.nextY += ball2.velocityY;

Answer 2

功能有错误collideBalls:

var direction1 = Math.atan2(ball1.velocitY, ball1.velocityX);

它应该是:

var direction1 = Math.atan2(ball1.velocityY, ball1.velocityX);