OOGL proposed as geometry format for VRML [plain text version]

[Paul Burchard <burchard at horizon.gw.umn.edu>]

I'd like to propose OOGL, an "object-oriented graphics language", as
the geometry and URL definition language for phase one of VRML.  See
[ http://www.geom.umn.edu/docs/software/viz/geomview/oogltour.html ]
for an introduction and the current specification.

OOGL was developed several years ago at the Geometry Center in
Minnesota [ http://www.geom.umn.edu/ ], and since that time it
has seen extensive testing as a geometric visualization format
in mathematics, physical sciences, and engineering.  See the
Center's Picture Archive (on the Web) for some interesting
examples of visualizations made with the help of OOGL.

The Geometry Center offers a free, extensible OOGL viewer, Geomview
[ http://www.geom.umn.edu/docs/software/viz/geomview/geomview.html ],
which runs on a variety of platforms.  You can also experiment with
OOGL directly from the Web using the interactive Cyberview forms
[ http://www.geom.umn.edu/apps/cyberview/about.html ] or
[ http://www.geom.umn.edu/apps/cyberview-x/about.html ]
(these forms require an HTML 2.0 compatible browser).

Among the advantages of OOGL:

* time-tested
* non-proprietary
* simple, compact syntax
        -- numerous converters exist to/from other formats
        -- easy to generate/parse in programs and scripts
        -- makes effective use of bandwith
* support for sophisticated graphics
        -- hierarchical objects, multiple instantiation
        -- appearance control, including color and normals
        -- polygons with shared vertices
        -- bezier patches
* support for hyperbolic geometry
        -- virtual reality with room for branched data structures

Following the Center for Innovative Computer Applications
[ http://www.cica.indiana.edu/graphics/viewing.3D.html ],
I propose the use of MIME type "object/x-oogl" (eventually
to become "object/oogl") by HTTP servers.

OOGL requires two simple extensions, which I hereby propose, to
serve as a Web-aware geometry language for VRML.  These extensions
have already been protoyped using a Geomview extension module.

1.  Its file include syntax "{ < filename }" should extend to
        cover URLs, not just local files.  This allows objects
        to be pulled into a single "world" from all over the Web.

2.  The syntax "{ > URL }" should be added as a way of defining
        HREF objects.  When an object is "picked" by the user, the
        viewer should determine the nearest HREF object (if any)
        above the picked object in the geometry hierarchy, and
        then follow the link so specified.  The recommended
        behaviors in following a link are:

        A. If the link points to another OOGL file, replace the
           current visible world with the new data (the old one
           may be retained as "history").

        B. If the link points to a higher-level control file,
           allow it to modify the current world directly.

        C. An external HTML viewer may be used to display links
           that are not handled by the VR viewer itself.


Note:  The Geomview viewer also supports a command/scripting
language for higher-level control, such as camera motion
(embedded OOGL is used for geometry definitions).  I will
submit that as a separate proposal when appropriate.

--------------------------------------------------------------------
Paul Burchard   <burchard at geom.umn.edu>
``I'm still learning how to count backwards from infinity...''
--------------------------------------------------------------------