Keep lowering 50.0f until it becomes an issue. You may be able to get closer than that but moving to the exact position will probably not happen.
To clarify:
- You need to factor the Z when converting 2D screen space into 3D world space.
- You do not need the Z when using Size( ) if your play space is a flat ground. (MouseLocation.Z and TargetLocation.Z are the same on a flat surface)
- You will need to factor in Z if you do not have a flat play space, as the distance of those two positions has a different Z value, factoring into the Size( ) calculation.