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Some criteria for VRML

  • To: software@geom
  • Subject: Some criteria for VRML
  • From: burchard
  • Date: Mon, 13 Jun 94 12:53:19 -0500

(Dave Raggett is the author of HTML+, a.k.a. HTML 3.0.  -PB)

Begin forwarded message:

From: Dave Raggett <dsr at hplb.hpl.hp.com>
Subject: Some criteria for VRML
To: www-vrml at wired.com
Date: Mon, 13 Jun 94 12:44:27 BST
Mailer: Elm [revision: 70.85]
Sender: www-vrml-owner at wired.com

I am off today to INET'94 to give my talk on VRML, and
thought it worthwhile to write down a few comments on what
I see as requirements that VRML should meet, if it is to be
widely useful:

To gain broad acceptance we will need freeware browsers
for Unix, PC and macs. I intend to develop a portable vrml
browser for Unix, based on the public domain PEX 3D
graphics extensions in X11.

VRML describes scenes as compositions of objects. VR
places a premium on efficient rendering, and so I believe
that objects will need to be specified for rendering at
different distance scales, rather than as a single 3D
geometric shape. The methods of interaction supported
by each object will vary according to how far away you are
from it. Thus as you walk up to a wall, the detail on the
clock appears and you begin to hear it ticking.
Similarly, the keys on a computer keyboard become
visible and allow you to type on the virtual keyboard.
Ditto for a virtual white board.

Objects can be described as a composition of
sub-objects. This allows you to reuse a given element
multiple times. PEX allows you to do specify the scene in
this way and then simply change your viewing position as
you move through the scene. The PEX server then does all
the work to render the scene without further
intervention by the application.

Another theme is to generate structures according to
rules, e.g. a tree as a set of branches with leaves,
Generative models would give VRML great power, e.g. to
populate an office with cubicles, or to generate a forest
of trees, or a landscape. One way to think of this is as a
genetic code together with a means of introducing
variations. Arbitrary complexity can be generated
*deterministically*, e.g. by using a random number
generator seeded with a predefined value.

Deterministic complexity will give us rich VR scenes
that take very little information to transmit, but
appear the same to each user regardless of which browser
is used. This is important when we want to meet in shared VR
scenes (virtual presence).

I will try and put flesh on these ideas when I get back from
Prague. In the meantime, please look at my paper (via

Best wishes,

Dave Raggett

Hewlett Packard Laboratories              email: dsr at hplb.hpl.hp.com
Filton Road                               tel:   +44 272 228046
Stoke Gifford                             fax:   +44 272 228003
Bristol BS12 6QZ
United Kingdom

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