you dont have to do that..
there is always a simpler way,
use helper sprites
most game devs use helper sprites to show what the player is looking at during run time
you can set the opacity of a helper FOV cone to zero
heres a capx to illustrate what I mean...you can change it to suit your needs
https://www.dropbox.com/s/tvr5ucp9124iut2/FOV%20%26%20LOS.capx?dl=0
there are hundreds of applications of this idea ..
hope it helps somehow