Provides medium to high level functions for 3D interactive graphics,
including functions modelled on base graphics (plot3d(), etc.) as well
as functions for constructing representations of geometric objects
(cube3d(), etc.). Output may be on screen using OpenGL, or to various
standard 3D file formats including WebGL, PLY, OBJ, STL as well as 2D
image formats, including PNG, Postscript, SVG, PGF.
