我需要检测圆形与任何线段的碰撞。我有一个包含多边形顶点坐标(x, y)的数组,并在循环中绘制此多边形。为了检测碰撞,我使用算法计算三角形高度。然后我检查这个高度是否小于0,如果是,则圆形与该线段发生了碰撞。
下面是描述此方法的图片:
但是我得到了意想不到的结果。我的圆形与透明线碰撞了(什么?)。我无法解释它是如何发生的。 在 jsfiddle 上查看演示:https://jsfiddle.net/f458rdz6/1/ 检查碰撞并响应的函数:var p = polygonPoints;
for (var i = 0, n = p.length; i < n; i++) {
var start = i;
var end = (i + 1) % n;
var x0 = p[start].x;
var y0 = p[start].y;
var x1 = p[end].x;
var y1 = p[end].y;
// detection collision
var dx = x1 - x0;
var dy = y1 - y0;
var len = Math.sqrt(dx * dx + dy * dy);
var dist = (dx * (this.y - y0) - dy * (this.x - x0)) / len;
if (dist < this.radius) {
continue;
}
// calculate reflection, because collided
var wallAngle = Math.atan2(dy, dx);
var wallNormalX = Math.sin(wallAngle);
var wallNormalY = -Math.cos(wallAngle);
var d = 2 * (this.velocityX * wallNormalX + this.velocityY * wallNormalY);
this.x -= d * wallNormalX;
this.y -= d * wallNormalY;
}
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var polygonPoints = [
{
x: 240,
y: 130
},
{
x: 140,
y: 100
},
{
x: 180,
y: 250
},
{
x: 320,
y: 280
},
{
x: 400,
y: 50
}
];
var game = {
ball: new Ball()
};
function Ball() {
this.x = canvas.width / 2;
this.y = canvas.height - 100;
this.oldX = this.x - 1;
this.oldY = this.y + 1;
this.velocityX = 0;
this.velocityY = 0;
this.radius = 8;
};
Ball.prototype.draw = function() {
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2);
ctx.fillStyle = '#0095DD';
ctx.fill();
ctx.closePath();
};
Ball.prototype.update = function() {
var x = this.x;
var y = this.y;
this.velocityX = this.x - this.oldX;
this.velocityY = this.y - this.oldY;
this.x += this.velocityX;
this.y += this.velocityY;
this.oldX = x;
this.oldY = y;
};
Ball.prototype.collision = function() {
var p = polygonPoints;
for (var i = 0, n = p.length; i < n; i++) {
var start = i;
var end = (i + 1) % n;
var x0 = p[start].x;
var y0 = p[start].y;
var x1 = p[end].x;
var y1 = p[end].y;
// detection collision
var dx = x1 - x0;
var dy = y1 - y0;
var len = Math.sqrt(dx * dx + dy * dy);
var dist = (dx * (this.y - y0) - dy * (this.x - x0)) / len;
if (dist < this.radius) {
continue;
}
// calculate reflection, because collided
var wallAngle = Math.atan2(dy, dx);
var wallNormalX = Math.sin(wallAngle);
var wallNormalY = -Math.cos(wallAngle);
var d = 2 * (this.velocityX * wallNormalX + this.velocityY * wallNormalY);
this.x -= d * wallNormalX;
this.y -= d * wallNormalY;
}
};
function drawBall() {
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
function drawPolygon() {
ctx.beginPath();
ctx.strokeStyle = '#333';
ctx.moveTo(polygonPoints[0].x, polygonPoints[0].y);
for (var i = 1, n = polygonPoints.length; i < n; i++) {
ctx.lineTo(polygonPoints[i].x, polygonPoints[i].y);
}
ctx.lineTo(polygonPoints[0].x, polygonPoints[0].y);
ctx.stroke();
ctx.closePath();
}
function render() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawPolygon();
game.ball.draw();
game.ball.update();
game.ball.collision();
window.requestAnimationFrame(render);
}
render();
canvas {
border: 1px solid #333;
}
<canvas id="myCanvas" width="480" height="320"></canvas>
谢谢。
interceptLines(line,line1)
发送哪些行吗?其中一条线应该是墙壁线,但第二条呢?我认为可以使用球的中心线(b.x, b.y)
作为一条线,那第二个点应该是什么呢?谢谢。 - rmpstmp