Geomview and OOGL are part of an ongoing effort at the Geometry Center
to provide interactive 3D graphics software which is particularly
appropriate for displaying the kinds of objects and doing the kinds of
operations of interest in mathematics research and education.  You can
compute an OOGL data file of a mathematical object that would be
difficult or impossible to build a model of in the real world.  In
geomview, besides examining an object in ordinary Euclidean 3-space,
you can look at objects in hyperbolic 3-space and Euclidean 4-space.
The hyperbolic model is the projective one, where geodesics are
straight lines and isometries are represented as 4x4 projective
matrices.  While geomview is tailored for mathematical visualization,
it is written to be extensible and can serve as a general-purpose
tool. Its functionality can be extended in an almost unlimited fashion
by external modules.