[X3D-Public] Examples for NURBS surface rendering in X3D

[Michalis Kamburelis]

Vincent Marchetti wrote:
> One thing I've found is that there is a divergence among these
> implementations as to how the parametric coordinate system is mapped
> onto the rendered surface, leading to a difference among the browsers
> in how they handle texturing and trimming.

X3D spec says "By default, texture coordinates in the unit square (or
cube for 3D coordinates) are generated automatically from the parametric
subdivision." Indeed, it doesn't say explicitly that nurbs U parameter
maps to 1st texture coord component (S) and nurbs V maps to 2nd texture
coord component (T). Anyway, that's how I understood it and explicitly
implemented in view3dscene, so at least in view3dscene this is by design :)

I think that you can submit this as InstantReality bug --- as all other
tested browsers agree, it seems that InstantReality should be just fixed
to follow.

For the solid field, note that I submitted some fixes (clarifications)
about it (see my mail on x3d-public
http://www.web3d.org/pipermail/x3d-public_web3d.org/2010-April/000708.html
), and (most of them) are incorporated in X3D 3.3 spec, see
http://web3d.org/x3d/specifications/ISO_IEC_PDAM1_19775_1_2008-X3D-AbstractSpecification/Part01/components/nurbs.html
. See the paragraph "When solid=TRUE is used ...".

So at least the interpretation of solid=TRUE is hopefully clearer in the
X3D 3.3 specification.

> 
> I look forward to discussing these results, I'd be particularly
> interested in finding out about any other implementations of the
> NURBS Component of X3D.
> 

You may be interested in White Dune,
http://vrml.cip.ica.uni-stuttgart.de/dune/ . This is an open-source
VRML/X3D modeler very focused on using NURBS surfaces for modeling. So
it may be useful to check it too. (Some low-level bits of view3dscene
NURBS implementation were actually made following White Dune code, as
we're both GPL.)

Michalis