方向问题地图谷歌地图 API

我的脚本有问题，我需要看到两点之间的路，函数directionsService.route（）返回状态"OK"，但在地图中我看不到路线！代码：

 <script type="text/javascript" >
    var dirService;
    var render;
    function calcolateRoute(){
        dirService = new google.maps.DirectionsService();

        var myOrigin = new google.maps.LatLng( 46.44664,12.381245);
        var myDestination = new google.maps.LatLng( 46.429516,12.373939);

        var mapOptions = {
                        zoom:15,
                        mapTypeId: google.maps.MapTypeId.ROADMAP,
                        center: myOrigin
                    };
        var map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);

        var renderOpt = {
            map:map,
            origin: myOrigin,
            destination: myDestination                  
            };

        render = new google.maps.DirectionsRenderer(renderOpt);

        render.setMap(map);

        var requestRoute = {
            origin: myOrigin,
            destination: myDestination,
            travelMode: google.maps.DirectionsTravelMode.DRIVING
        };
        dirService.route(requestRoute, function(result, status){
                if(status == google.maps.DirectionsStatus.OK){
                    render.setDirection(result);
                    alert(status);                  
                }else{
                    alert(status);

                }
            });
    }
    google.maps.event.addDomListener(window, 'load', calcolateRoute);
</script>

谢谢大家的帮助