gistfile1.as

package ru.k0t0vich.utils.math {
    import flash.geom.Point;

    public class IntersectUtil {

        public static function getLinesIntersectionPoint(a1:Point, a2:Point, b1:Point, b2:Point):Point {
            var d:Number = (a1.x - a2.x) * (b2.y - b1.y) - (a1.y - a2.y) * (b2.x - b1.x);
            var da:Number = (a1.x - b1.x) * (b2.y - b1.y) - (a1.y - b1.y) * (b2.x - b1.x);
            var db:Number = (a1.x - a2.x) * (a1.y - b1.y) - (a1.y - a2.y) * (a1.x - b1.x);

            if (Math.abs(d) < 0.000001) {
                return null;
            } else {
                var ta:Number = da / d;
                var tb:Number = db / d;
                if ((0 <= ta) && (ta <= 1) && (0 <= tb) && (tb <= 1)) {
                    var x:Number = a1.x + ta * (a2.x - a1.x);
                    var y:Number = a1.y + ta * (a2.y - a1.y);
                    return new Point(x, y);
                }
            }
            return null;
        }

        public static function getPoligonsIntersectionPoints(polygone1:Array,
                poligone2:Array):Array {
            var len1:uint = polygone1.length;
            var len2:uint = poligone2.length;
            var result:Array = [];

            for (var i:int = 0; i < len1; i++) {
                var p1:Point = Point(polygone1[i]);
                var p2:Point = Point(polygone1[(i + 1) % len1]);

                for (var j:int = 0; j < len2; j++) {
                    var p3:Point = Point(poligone2[j]);
                    var p4:Point = Point(poligone2[(j + 1) % len2]);

                    var intersection:Point = getLinesIntersectionPoint(p1, p2, p3, p4);
                    if (intersection) {
                        result.push(intersection);
                    }
                }
            }
            return result.length > 0 ? result : null;
        }

    }
}