Grouping nodes are used to group shapes to compose complex shapes.
The Switch node creates a switched group where only one child node in the group is displayed, children implicitly numbered from 0
and a whichChoice value of -1 selects no children.
Transform creates a group with its own coordinate system where every child node in the group is displayed.
Billboard creates a group with a special coordinate system that turns to face the viewer.
These X3D scenes are adapted directly from the
original VRML 2.0 Sourcebook chapter examples.
Introduction to VRML97 SIGGRAPH98 course notes.