From: thinman@netcom.netcom.com (Lance Norskog)
Subject: Re: TECH: REND386: adding motion
Date: Thu, 6 Feb 92 12:04:45 PST



In sci.virtual-worlds Dwayne Jacques Fontenot writes:

>You have just described PHIGS (Programmer's Hierarchical Interactive 
>Graphics System). 

>Well, to be correct, you have just described the general idea behind
>hierarchical graphics systems, of which PHIGS is one. I mention this
>because a) you mentioned standards, and PHIGS is an ANSI/ISO standard,
>and b) I happen to work in PHIGS.

>I too am working on shared VR worlds, in PHIGS, so I guess we are
>working on similar projects.

>Looking forward to hearing more discussion on this,

You asked for it!

PHIGS is, as far as I can tell, a CAD system.  We need something where
we can download real code anywhere we can download anything.

Also, PHIGS is a comittee-created standard; 8 years of endless rounds
of meetings in far-away places.  The only good standards are 
those where the comittee was forced to rubber-stamp an existing
standard that had succeeded in the market.  See "The Open Book"
by Marshall Rose for more on this topic.

I'm building a system which uses a two-tier approach: the top tier
is a Scheme interpreter, and the bottom tier is a heirarchically
organized dataflow system similar to VPL's basic world-building language.
The dataflow system has constructs like "the mouse vector outputs a
synchronous stream of numbers, and the box position accepts this
stream of numbers"; you move the mouse and the box moves.

The collection of dataflow graphs are clocked synchronously,
and can subscribe to the vertical retrace clock, the 1-second
clock, and various interesting events.  The Scheme interpreter 
has the ability to create and move these dataflow graphs around,
and talks to others of its kind over the network.  Scheme is a
very simple, stripped-down, but still complete, version of LISP.

Writing VR stuff in C, Pascal, etc. allows you to build simple
things that run very fast, but you can't go very far with them.
Those software tools aren't up to building a long-term
communal software base.

Lance Norskog
thinman@netcom.com