Change the mash visibility by camer rotation?

I want to know how to show this Cylinder by camera rotation

when the player enter the collision the Cylinder will be off but if the player rotated 180 degree in Z Axis than turned back the cylinder visibility will be on

Like this for example : letters disappear when he rotate \


I think this should help you

As long as you run this only when the player is within the collision area, you should be able to use this to trigger an event when the cylinder is off screen.