A 3D spatial element representing a plane of infinite extent, which is
defined by a normal vector and a (possibly negative) distance from the
origin along the vector.
Plane3() -
Constructor for class gumbo.graphic.math.Plane3
Creates an instance, with zero distance,
and a default unit vector normal.
Informs this graphic entity that, in anticipation of realization,
it should update as needed those aspects of its graphic state
(geometry, appearance) and that of any dependents (siblings,
descendants) that can affect its presentation.
Called by the system (this class) when this node needs to process
an event, whether the event is received through a connection or results
from a set() method.
The default implementation: If the trigger is cancelled
and cancel in goes false, starts the reset state; else, if the
trigger is captured and cancel in is true, starts the cancel state.