The exit of this portal. The portal camera renders what it sees through the exit portal and teleports take you there.
This property is REQUIRED, it can never be null.
This property can be changed during gameplay to switch the destination of this portal.
TIP: Commonly, two portals have eachother as their exits, but, you can also try one-way portals and self-as-exit as well!
public Portal3D ExitPortal { get; set; }