Extrusion geometry is defined by a 2D cross-section that is stretched and rotated around a central spine.
Extruded shapes are very common: tubes, pipes, bars, vases, donuts, and other tricky uses.
An Extrusion node efficiently creates extruded shapes.
The crossSection field specifies the cross-section, and the spine field specifies the sweep path.
The scale and orientation fields specify scaling and rotation at each spine point.
These X3D scenes are adapted directly from the
original VRML 2.0 Sourcebook chapter examples.
Introduction to VRML97 SIGGRAPH98 course notes.