使用 JQuery 检测两个旋转的 div 是否碰撞

Question

我想检测两个旋转的 div 是否发生碰撞。如果它们不旋转，我知道该怎么做，但是当它们实际旋转时，我不知道该怎么做。

我尝试了一些碰撞插件，例如jQuery Collision (http://sourceforge.net/projects/jquerycollision/)，但是当div旋转时它们都不起作用。

我使用 CSS 的 transform 属性对 div 进行了旋转。

Answer 1

它不是 100% 准确，但它确实适用于大多数情况，我使用了来自 here 的算法：

function isUndefined(a) {
    return a === undefined;
}

/**
 * Helper function to determine whether there is an intersection between the two polygons described
 * by the lists of vertices. Uses the Separating Axis Theorem
 *
 * @param a an array of connected points [{x:, y:}, {x:, y:},...] that form a closed polygon
 * @param b an array of connected points [{x:, y:}, {x:, y:},...] that form a closed polygon
 * @return true if there is any intersection between the 2 polygons, false otherwise
 */
function doPolygonsIntersect (a, b) {
    var polygons = [a, b];
    var minA, maxA, projected, i, i1, j, minB, maxB;

    for (i = 0; i < polygons.length; i++) {

        // for each polygon, look at each edge of the polygon, and determine if it separates
        // the two shapes
        var polygon = polygons[i];
        for (i1 = 0; i1 < polygon.length; i1++) {

            // grab 2 vertices to create an edge
            var i2 = (i1 + 1) % polygon.length;
            var p1 = polygon[i1];
            var p2 = polygon[i2];

            // find the line perpendicular to this edge
            var normal = { x: p2.y - p1.y, y: p1.x - p2.x };

            minA = maxA = undefined;
            // for each vertex in the first shape, project it onto the line perpendicular to the edge
            // and keep track of the min and max of these values
            for (j = 0; j < a.length; j++) {
                projected = normal.x * a[j].x + normal.y * a[j].y;
                if (isUndefined(minA) || projected < minA) {
                    minA = projected;
                }
                if (isUndefined(maxA) || projected > maxA) {
                    maxA = projected;
                }
            }

            // for each vertex in the second shape, project it onto the line perpendicular to the edge
            // and keep track of the min and max of these values
            minB = maxB = undefined;
            for (j = 0; j < b.length; j++) {
                projected = normal.x * b[j].x + normal.y * b[j].y;
                if (isUndefined(minB) || projected < minB) {
                    minB = projected;
                }
                if (isUndefined(maxB) || projected > maxB) {
                    maxB = projected;
                }
            }

            // if there is no overlap between the projects, the edge we are looking at separates the two
            // polygons, and we know there is no overlap
            if (maxA < minB || maxB < minA) {
                console.log("polygons don't intersect!");
                return false;
            }
        }
    }
    return true;
};

$('#r').click(function() {
    var rota = Math.floor( Math.random() * 100 ),
        rotb = Math.floor( Math.random() * 100 ),
        pointsa = new Array(4),
        pointsb = new Array(4);

    $('#a').css('transform', 'rotateZ(' + rota + 'deg)');
    $('#b').css('transform', 'rotateZ(' + rotb + 'deg)');

    $('#a div').each(function(i) {
        pointsa[i] = {x: parseInt($(this).offset().left), y: parseInt($(this).offset().top)};
    });

    $('#b div').each(function(i) {
        pointsb[i] = {x: parseInt($(this).offset().left), y: parseInt($(this).offset().top)};
    });


    $('#s').val("intersection: " + doPolygonsIntersect(pointsb, pointsa).toString());
});

working fiddle

我猜这不是最好的方法，我的脚本所做的基本上是在 0 到 100 度之间随机旋转，获取每个角的 x 和 y 位置（使用 div，你可以用数学来做到这一点，也（我不能：D））并使用这些坐标运行算法。

Answer 2

您正在寻找 div 碰撞检测。

如果要引发事件，则必须反复测试，但最好只在所有 div 上运行该函数。

示例演示位于http://jsfiddle.net/nGRwt/7/

这是你需要使用的功能

function collision($div1, $div2) {
      var x1 = $div1.offset().left;
      var y1 = $div1.offset().top;
      var h1 = $div1.outerHeight(true);
      var w1 = $div1.outerWidth(true);
      var b1 = y1 + h1;
      var r1 = x1 + w1;
      var x2 = $div2.offset().left;
      var y2 = $div2.offset().top;
      var h2 = $div2.outerHeight(true);
      var w2 = $div2.outerWidth(true);
      var b2 = y2 + h2;
      var r2 = x2 + w2;

      if (b1 < y2 || y1 > b2 || r1 < x2 || x1 > r2) return false;
      return true;
    }

另一个演示

您也可以参考http://jsfiddle.net/98sAG/ 进行碰撞检测。

为此使用以下代码：

var overlaps = (function () {
    function getPositions( elem ) {
        var pos, width, height;
        pos = $( elem ).position();
        width = $( elem ).width();
        height = $( elem ).height();
        return [ [ pos.left, pos.left + width ], [ pos.top, pos.top + height ] ];
    }

    function comparePositions( p1, p2 ) {
        var r1, r2;
        r1 = p1[0] < p2[0] ? p1 : p2;
        r2 = p1[0] < p2[0] ? p2 : p1;
        return r1[1] > r2[0] || r1[0] === r2[0];
    }

    return function ( a, b ) {
        var pos1 = getPositions( a ),
            pos2 = getPositions( b );
        return comparePositions( pos1[0], pos2[0] ) && comparePositions( pos1[1], pos2[1] );
    };
})();

希望对你有帮助:)

Answer 3

我找到了 yckart 的 overlaps.js。

我在这里摆弄了旋转的 div：http://jsfiddle.net/n3M5e/

你可以自己改变CSS中div的旋转，检测效果还是不错的。

overlaps.js：

(function ($) {
    $.fn.overlaps = function (obj) {
        var elems = {
            targets: [],
            hits: []
        };
        this.each(function () {
            var bounds = $(this).offset();
            bounds.right = bounds.left + $(this).outerWidth();
            bounds.bottom = bounds.top + $(this).outerHeight();

            var compare = $(obj).offset();
            compare.right = compare.left + $(obj).outerWidth();
            compare.bottom = compare.top + $(obj).outerHeight();

            if (!(compare.right < bounds.left || compare.left > bounds.right || compare.bottom < bounds.top || compare.top > bounds.bottom)) {
                elems.targets.push(this);
                elems.hits.push(obj);
            }
        });

        return elems;
    };
}(jQuery));

希望我有所帮助。

编辑：

感谢@jbrosi，overlaps.js 并不能很好地处理旋转的 div。