xmgf by Paul Hoad (P.Hoad@ee.surrey.ac.uk) is an interactive tool for viewing
2D and 3D objects typically in gf/OFF/NFF/IGRIP/MINICAD/SLA/DXF format
Sources are on ftp.x.org.  Version 1.9.1 became available 12/93.

x3d is a V.Fast 3D Object viewer for X it needs no special hardware or or
widget libraries other that X and is optimized for speed.

XGobi can be used to to view such data.
	
VOGLE can be used to to view such data.

An interactive 3D viewer based on the X Window System is "Geomview";
information is available at
http://www.geom.umn.edu/software/geomview/docs/gvpeek.html .

xdim 2.6 is available [1/96] from
ftp://ftp.uni-stuttgart.de//pub/unix/X11/graphics/xdim/xdim2_6.tar.gz .  XDim
combines features from data processing (p.ex. import from table calc.
programs) and image processing (p.ex. import GIF's and JPEG's) with an
interactive 3D Viewer and Motif user interface.

Grapher-3D generates surfaces of two variable functions allowing users to
view these surfaces from any three dimensional position.  Dynamic axis
rotation and domain shifting help better illustrate the nature of a
function.  Sources are on ftp.x.org in contrib/graphics/Grapher-3D/,
including source grapher-3d-1.2.tar.gz and some binary sets. [3/96]

Also of use:

Hv (for Hot Views)  is a library that greatly simplifies the development of
applications with a sophisticated graphical user interface. It is layered on
top of X, Xt (R4 or later), and OSF Motif (version 1.1 or later); however,
the developer is completely insulated from those libraries. Information:
heddle@cebaf.gov. Sources are on ftp://ftp.cebaf.gov/pub/heddle/Hv/ .