What are Nurbs ?

NURBS means "Non-Uniform Rational B-Splines". In short, NURBS can be used to build rounded faces by transfering only very few data. A mathematical formula is used to construct the faces.

My browser do not understand "NurbsSurface"

NurbsSurface (and other Nurbs objects) are part of the ISO/IEC14772-1:1997/Amd. 1:2002(E) VRML standard. Some VRML97 browsers like cc3d or cortona already have the NurbsSurface Node available, while most other browsers do not support it yet.

White_dune support the VRML Amendment 1 NurbsSurface, but this would be useless for other browsers.

For the Cosmo Player browser (at least the version 2.1.5 on IRIX and and the version 2.1.1 on M$Windows), it is possible to use a NurbsSurface PROTO written in javascript to make use of the NurbsSurface node (texCoord not supported yet).

To view NurbsSurface nodes with the Cosmo Player browser you need to include this EXTERNPROTO declaration in your VRML file (e.g. by using File -> import in white_dune).
Other Browsers with NurbsSurface support will fall back to their own (very much faster) implementation.

Click here (and be patient till the accounting is ready) if you have the Cosmo Player browser (at least the version 2.1.5 on IRIX or version 2.1.1 on M$Windows work) to see a example of the usage of the NurbsSurface EXTERNPROTO.