Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu!woolstar
From: woolstar@nntp-server.caltech.edu (John D. Woolverton)
Newsgroups: comp.graphics
Subject: Scene Description Standard (Renderman isn't good enough)
Message-ID: <1991Apr30.211131.7166@nntp-server.caltech.edu>
Date: 30 Apr 91 21:11:31 GMT
Organization: California Institute of Technology, Pasadena
Lines: 41


   I would love to have a standard interface to work with
(from both sides: modeling and rendering).  However my investigation
of RenderMan has been _very_ dissapointing.

   Perhapse to the world of 3D Z-buffers and other scan line
rendering programs, RenderMan is enough.  But for work in
RayTracing and beyond, there are too many things missing.

   Conceptually, Renderman seems to be designed like PostScript.
One renderman file, one image.  While this works for the printed
page, animations and 3D graphics have continuity across frames
that RenderMan cannot describe or take advantage of.
   Renderman is also grossly inefficient for representing
polygons, as it takes a [vertex, vertex, vertex, close] form for
representing each face instead of a list of verteces and then a
face list.
   Finally the concept of an actor/object is non-existant
in RenderMan.  There is no grouping of faces with different
properties or relationships defined.

   While one could take one's own model from another system
and extract the Renderman Commands for it, it does not seem
possible to go the other way.  Witness all the modeling programs
that support the RenderMan interface, but use their own 
formats for working data (scene and objects).  [all of them!]

   PLEASE SOMEONE!  Work on a scene description file format
that will describe an animation or scene, not just the
resultant list of polygons.

My proposal:
	One object format that includes geometry primatives
and surface descriptions.
	One model format that describes position and motion
of objects in a scene.
	Extentions to both for specific shading and 
(for ray tracing) geometry organization (bounding boxes...).

	John D. Woolverton, Video Bits
	woolstar@cobalt.caltech.edu