html5画布中的碰撞检测

Question

我正在尝试构建一个游戏,用户应该将圆圈放在垂直条中,但我在碰撞检测功能方面遇到了麻烦.这是我的jsfiddle:http://jsfiddle.net/seekpunk/QnBhK/1/

 if (collides(Bluecircle, longStand)) {
    Bluecircle.y = longStand.y2;
    Bluecircle.x = longStand.x2;
 }
 else if (collides(Bluecircle, ShortStand)) {
    Bluecircle.y = ShortStand.y2;
    Bluecircle.x = ShortStand.x2;
 }
function collides(a, bar) {
   return a.x == bar.x1 && a.y == bar.y1;
}

Answer 1

[编辑修正错字和遗漏]

以下是如何对碰撞测试矩形和圆形:

演示:http://jsfiddle.net/m1erickson/n6U8D/

    var circle={x:100,y:290,r:10};
    var rect={x:100,y:100,w:40,h:100};

    // return true if the rectangle and circle are colliding
    function RectCircleColliding(circle,rect){
        var distX = Math.abs(circle.x - rect.x-rect.w/2);
        var distY = Math.abs(circle.y - rect.y-rect.h/2);

        if (distX > (rect.w/2 + circle.r)) { return false; }
        if (distY > (rect.h/2 + circle.r)) { return false; }

        if (distX <= (rect.w/2)) { return true; } 
        if (distY <= (rect.h/2)) { return true; }

        var dx=distX-rect.w/2;
        var dy=distY-rect.h/2;
        return (dx*dx+dy*dy<=(circle.r*circle.r));
    }

[补充说明澄清]

...这就是测试圆是否完全包含在矩形中的方法

演示:http: //jsfiddle.net/m1erickson/VhGcT/

// return true if the circle is inside the rectangle
function CircleInsideRect(circle,rect){
    return(
        circle.x-circle.r>rect.x &&
        circle.x+circle.r<rect.x+rect.w &&
        circle.y-circle.r>rect.y &&
        circle.y+circle.r<rect.y+rect.h
    )
}