I have followed the debates about VRML/X3D for weeks, and it's time to speak.

The aim of our project is to make botanical data available on Internet, including 3D images.

We need a compact, non proprietary, preferably XML, clean definition for complex 3D geometries.

It seems that a representation both compact and flexible should be based on  mathematics. VRML's cones and cylinders are just special cases of intersections of volumes defined by equations:
f(x,y,z)>=0

NURBS and Beziers patches are just special cases of surfaces defined by 3 functions R2 ---> R3
(u,v) ---> (X(u,v),Y(u,v),Z(u,v))

A solution is to use the content part of MathML. I have reviewed it: it has the desired capabilities, i.e. allows to define functions and sets, it is XML. Certainly only a subset of MathML is needed: n-dimentional geometry, n>3 is not relevant. On the other hand, some geometrical primitives could be added :
- convex hulls,
- recursive constructs like fractals and L-systems,
- transforms, deformations, parametrization, movement
 

My second point is about modular schemas versus monolythic Schemas. X3D is a very "good" example of monolythic DTD. NOTHING is taken from the XML world outside X3D.

It seems that Virtual Reality involves several layers that can be used and designed independently:
- volumic objects definition (see above)
- colors and textures on volumic objects
- behavior of volumic objects among them (contact, glued or sliding, rotating, interpenetrable, etc)
- behavior of volumic objects with User Interface
- a scene as composite Design pattern of volumic objects
- light sources
- scenarios (time-dependant aspect )
- sounds

Conclusion:

This need for a compact, non proprietary, preferably XML, clean definition for complex 3D geometries is common with other important domains:
- Computer Aided Design
- Architecture
- simulation in mechanics, physics, and biology

CAD is a very important field that has currently no XML non-proprietary language. It seems that the proposed solution could bring an interesting synergy able to speed up developments, together with a better design. And also a common subset for CAD and Virtual Reality will bring new possibilities to exchange data.
A well-designed model and XML syntax for virtual reality could also be used for cartoons and video games.
 

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<person>
  <first_name>Jean-Marc</first_name>
  <name>Vanel</name>
  <project>Worlwide Botanical Knowledge Base -
      making botany available on Internet
    <a href="http://wwbota.free.fr/" >site</a>
  </project>
  <homePage>http://jmvanel.free.fr/</homePage>
  <a href="mailto:jmvanel@free.fr">mail (eventually put "wwbota" in subject to route your mail in relevant folder)</a>
</person>