Re: WEB : Mapping out communal cyberspace

John W. Barrus (
Tue, 14 Jun 1994 10:57:38 -0400

>From Jerry Isdale:
>re: object sharing
> Transfering entire geometries across the net whenever you enter a new
>space will absolutely kill your bandwidth. Especially if your VRML (or VR
>Interchange Format - an alternative evolving standard) gives vertex coords
>in ascii text.
> Consider instead that you have at each client machine a library of object
>geometries (and possibly some behaviors). The VRML would then need only
>specify that a "teapot:utah" is needed instead of sending the 500 polys
>needed. The client would look up the symbolic name in its database and pull
>the appropriate level of detail and format required by its image
> Object libraries could be distributed on CDROM in some common format,
>with symbolic indexing database. If the object is new to the local client,
>it could request a copy from the server (perhaps not the same one the VRML
>document resides upon, but a different 'geometry server')

I'm having a little trouble with this line of thought. I think that one of
the most interesting thing about 3D environments is seeing what new and
interesting things people have done. If we depended on a pre-defined set
of objects (which we could view at our leisure from the CD-ROM) and the
only thing different about the scene is which objects are contained in it
and how they are arranged, I'm going to get bored fairly quickly. I would
rather build my office and let people see where I work than have a chair
#6, bookshelf #21 and desk #3 arranged in a scene. I compare it to
prerecording every syllable and instead of transfering the actual sound
from a link, transfer a list of syllables to play back in order in the name
of saving bandwidth. It limits what you can say (forget music and singing)
and is very annoying.

Bandwidth will suffer with 3D environments. However, if I want to watch a
movie that is in the WWW, _I_ decide whether or not to download it based on
how big I think it is and how long I am willing to wait. By the way, I
firmly believe that a 3D scene will require more space than a single
picture, but a lot less space than a movie of the same scene.

Barcelona is a model of a building in Spain with about 3300 polygons.
There are several rooms, a pool, a sculpture, several chairs, at least one
desk, etc. Perhaps someone reading this knows more about the model. I
have seen it at SIGGRAPH. I counted the polygons in the Inventor model on
our machine here at MERL. The model includes a list of material
definitions, a list of normals, and a list of points (coordinates), and a
list of indeces for the polygons->point mapping. Many of the polygons have
more than 10 vertices, but I didn't do a histogram.

The binary version of the model on an SGI is 225kb (Open Inventor format).
The Open Inventor Ascii Interchange format version is 841kb.
The COMPRESSED Ascii version (Barcelona.iv.Z) is 190kb.
I have not seen any movies less than 190kb (but I haven't looked for small
movies either).

Also, even though the interchange format will most likely be ASCII, we
would be foolish not to build some type of compression into the reader,
even if it is just RLE, because the ASCII files are always loaded with
whitespace for human readers.

> It is essential (IMNSHO) that the VRML/VRIF be completely in the public
>domain, available on the net and freely reproducable in vendor


>Jerry Isdale
>System Engineer
>Illusion, Inc.

John B.


John Barrus

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