Construct a new Point3D object. All parameters are optional. Unset parameters will be set to null. Remember, all units for member variables are meters.
By default, +x is to the right and -x is to the left. Units for this member variable are meters.
By default, +y is into the screen and -y is out of the screen towards the user. Units for this member variable are meters.
By default, +z is up and -z is down. Units for this member variable are meters.
Instantiations of this class define a position in 3D space. The position of a user affects the way the mixed spatial audio is heard by the user.