如何检查一个游戏对象是否可以看到另一个游戏对象？

I have an object, that is facing a particular direction with (for instance) a 45 degree field of view, and a limit view range. I have done all the initial checks (Quadtree node, and distance), but now I need to check if a particular object is within that view cone, (In this case to decide only to follow that object if we can see it). I have an object, that is facing a particular d