Viewpoints are the primary way for an author to show users what is in a scene,
helping them navigate among objects of interest.
Viewpoint nodes specify a desired location, an orientation, and a camera field-of-view lens angle.
By default, the viewer enters a world at position (0, 0, 10) and is looking along the -Z axis towards the origin.
You can provide your own preferred viewing locations and directions in Viewpoint nodes.
The first Viewpoint in the scene is the initial entry Viewpoint.
These X3D scenes are adapted directly from the
original VRML 2.0 Sourcebook chapter examples.
Introduction to VRML97 SIGGRAPH98 course notes.