public static function LineVsLine(v1 : Vector2, v2 : Vector2, v3 : Vector2, v4: Vector2) {

        var zn = (v4.y-v3.y)*(v2.x-v1.x)-(v4.x-v3.x)*(v2.y-v1.y);

        var ua = ((v4.x-v3.x)*(v1.y-v3.y)-(v4.y-v3.y)*(v1.x-v3.x))/zn;

        var ub = ((v2.x-v1.x)*(v1.y-v3.y)-(v2.y-v1.y)*(v1.x-v3.x))/zn;

        if ((ua>=0 && ua <=1) && (ub>=0 && ub <=1)) return true;

        return false;

}

var p0:MovieClip = createPoint(170,270);

var p1:MovieClip = createPoint(300,100);

 

var a:MovieClip = createPoint(200,200);

var b:MovieClip = createPoint(300,200);

var c:MovieClip = createPoint(300,300);

var d:MovieClip = createPoint(200,300);

 

onEnterFrame = function()

{

        _root.clear();

 

        var hit:Boolean = true;

 

        var dx:Number = p1._y-p0._y;

        var dy:Number = p0._x-p1._x;        

        var s0:Number = (a._x-p0._x)*dx+(a._y-p0._y)*dy;

        var s1:Number = (b._x-p0._x)*dx+(b._y-p0._y)*dy;

        var s2:Number = (c._x-p0._x)*dx+(c._y-p0._y)*dy;

        var s3:Number = (d._x-p0._x)*dx+(d._y-p0._y)*dy;        

        if(        (s0> 0&&s1> 0&&s2> 0&&s3> 0)||

                (s0<=0&&s1<=0&&s2<=0&&s3<=0))hit=false;

 

        beginFill((hit)?0xff0000:0x00ff00);

        moveTo(a._x,a._y);

        lineTo(b._x,b._y);        

        lineTo(c._x,c._y);        

        lineTo(d._x,d._y);        

        endFill();

 

 

        lineStyle(1);

        moveTo(p0._x,p0._y);

        lineTo(p1._x,p1._y);        

}

function createPoint(x:Number,y:Number):MovieClip

{

        var i:Number = getNextHighestDepth();

        var p:MovieClip = createEmptyMovieClip("point"+i.toString(),i);

        p.beginFill(0);

        p.lineTo(7,0);

        p.lineTo(0,7);

        p.endFill();

        p._x = x;

        p._y = y;

        p.onPress = function(){this.startDrag();}

        p.onMouseUp = function(){this.stopDrag();}

        return p;

}