Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!rocksanne!bozo!kirby
From: kirby@bozo.wbst128.xerox.com (Mike Kirby (co-op))
Newsgroups: comp.graphics
Subject: Re: 3D object file formats
Keywords: file formats, 3D
Message-ID: <718@rocksanne.UUCP>
Date: 14 Apr 89 16:15:40 GMT
References: <30686@sgi.SGI.COM>
Sender: news@rocksanne.UUCP
Reply-To: kirby@bozo.UUCP (Mike Kirby (co-op))
Organization: WRC, XEROX
Lines: 57


>I am looking for information on 3-D object file formats; if you have
>a lot of experience with 3D formats, or know of any relevant
>references, I would appreciate E-mail, or, if you think this might be
>of general interest, a response in this newsgroup.

Hmmm, Well....I just happen to be developing one of those "yet another
format" for description of three-d objects.  It is based on an object
oriented approach to everything.  I think perhaps this might be something
along the lines of what you want, because if you forget anything, then
you simply create another message.  For example.

define bluesphere {
   color setcolor [0.0 0.0 1.0];
   sphere (radius #f ) (center []);
}

this definition indicates that a sphere should be defined as having the
properties of the following objects : color and sphere.  Color is passed the 
message "setcolor" (a little redundant, yes..I know) and a "point_type" which
is enclosed within square brackets.  

A sphere type takes 2 messages, radius and center.  In this case, they are
left as implicitly defined (i.e. they are passed in as messages when
the object blueshpere is used).  Explicit definitions (like setcolor) are
constant within the confines of the sphere.

Now, if you wanted to expand it and include textureing, you could do
something like this:

define bumpyblue {
   bluesphere (radius #f) (center[]);
   maptexture filename "/usr/textures/texture1" method inverse_spherical;
}

Here, we have taken our bluesphere and again, passed the implicit definitions
along and included a new object called maptexture.  maptexture takes
two messages, a filename (all string types are enclosed within "") and
a method.  The method type is one of several predefined texturing methods.

With what you seem to have in mind you could simply begin adding on more
and more objects as you see fit.  The specification would remain compatible
with previous version, and also continue to have new features.

Note, that the environment has not been defined as of yet.  In my system
it is always done first with the definition of a special object ENVIRONMENT.

Comments? Suggestions? I am still developing this idea, and would appreciate
comments. I like this method because (although verbose in 
some aspects), it is easy to construct complicated images, and it is
easy to implement.  while I was defining it, I was careful to keep
implementation details in mind.

Michael Kirby
mpk9172@ritvax.bitnet		(This works)
mpk9172%ritcv@cs.rit.edu	(this is a little flaky, but usually works)
kirby.wbst128@xerox.com		(never tried this one)