Subject: Clarification of 3DM NP

From: Barbara Lurvey O/o <[email-masked]>
Date: 26 May 1995 10:58:54 -0400

Dear SC24 colleagues,
   
I have been asked several questions about the U.S. proposed new work item for a
Three-Dimensional Metafile for Computer Graphics (3DM). 
    1.  How does this NP relate to SGI's Open Inventor work?  Is it to validate
the 
         the SGI work or to be an anti-SGI effort?	
    2.  Doesn't SC24 already have a 3D metafile in the PHIGS Archive protocols?

I want to share my responses with all of you.
  
1. Requirements for standardizing a 3D Metafile for Computer Graphics have been
considered since SC24 was first established and several efforts have actually
been started. The US recognized last year that time is running out for such an
effort and thus solicited contributions from the computer graphics community. 
In October, 1994, presentations were made to our X3H3 technical committee
members by representatives of Apple Computer, Silicon Graphics (SGI), and
InterCap.  A report was also received recommending the use of STEP.

The important shared observations from these presentations were:
	- The need for a 3D cross-platform graphics format was recognized as an
	  urgent requirement by most developers.  The market is currently 
	  hindered by the lack of such a standard.
	- The markets that must be addressed are broad and horizontal in 
	  nature, rather that narrow and vertical.
A decision followed to try to leverage the work on SGI's Open Inventor.  The
Open Inventor file format (not the application environment) was chosen as the
basis for this work.  A review of this format indicates that, unlike OpenGL,
the functionality involved is similar to PHIGS.  The file is intended to be a
picture capture metafile which also retains the structure of the data so that
the information can be modified at the interpreter end. There was a careful
assessment made of  the organization's willingness to contribute designs and
modify them in order to produce a single ISO 3D Metafile standard as well as
the commercial acceptance and availability the current work.  SGI has been most
cooperative, including offering a project editor.
     
2. In CGRM terms, the intent of 3DM is to capture "scenes" at the virtual
environment level whereas the PHIGS archive files capture all or part of the
collection store at the construction environment level.  

3DM is intended for interchange of 3D scenes at the PHIGS Workstation level.  A
scene database is defined which contains shapes, properties and other aspects
of the graphical "elements" being described.  Light and cameras give the
information necessary to render the "elements."    

I hope this helps,
Barb