I have a problem with a game i am programming. I am making some sort of security game and i would like to have some visual line of sight. The problem is that i can't restrict my line of sight so my cops can't see through the walls. Below you find the design, in which they can look through windows, but not walls. Further below you find an illustration of what my problem is exactly.

this is what it looks like now. As you can see, the cops can see through walls.

This is the map i would want to use to restrict the line of sight.

So the way i am programming the line of sight now is just by calculating some points and drawing the sight accordingly, as shown below. Note that i also check for a hittest using bitmapdata to check whether or not my player has been spotted by any of the cops.

private function setSight(e:Event=null):Boolean
{
    g = copCanvas.graphics;
    g.clear();

    for each(var cop:Cop in copCanvas.getChildren())
    {
        var _angle:Number = cop.angle;
        var _radians:Number = (_angle * Math.PI) / 180;
        var _radius:Number = 50;

        var _x1:Number = cop.x + (cop.width/2);
        var _y1:Number = cop.y + (cop.height/2);
        var _baseX:Number = _x1 + (Math.cos(_radians) * _radius);
        var _baseY:Number = _y1 - (Math.sin(_radians) * _radius);

        var _x2:Number = _baseX + (25 * Math.sin(_radians));
        var _y2:Number = _baseY + (25 * Math.cos(_radians));
        var _x3:Number = _baseX - (25 * Math.sin(_radians));
        var _y3:Number = _baseY - (25 * Math.cos(_radians));

        g.beginFill(0xff0000, 0.3);
        g.moveTo(_x1, _y1);
        g.lineTo(_x2, _y2);
        g.lineTo(_x3, _y3);
        g.endFill();
    }

    var _cops:BitmapData = new BitmapData(width, height, true, 0);
    _cops.draw(copCanvas);

    var _bmpd:BitmapData = new BitmapData(10, 10, true, 0);
    _bmpd.draw(me);

    if(_cops.hitTest(new Point(0, 0), 10, _bmpd, new Point(me.x, me.y), 255))
    {
        gameover.alpha = 1;
        setTimeout(function():void{ gameover.alpha = 0; }, 5000);
        stop();

        return true;
    }

    return false;
}

So now my question is: Is there someone who knows how to restrict the view so that the cops can't look through the walls? Thanks a lot in advance.

ps: i have already looked at this tutorial by emanuele feronato, but i can't use the code to restric the visual line of sight.