[x3d-public] ifs defaults

[Andreas Plesch]

Use of DOM methods via d3 to build up a scene brought up an issue with the
default IndexedFaceSet node.

While many geometry nodes have renderable defaults, IFS and other composed
geometry nodes have a NULL coord field as default which makes the default
node undefined. There are two consequences. Different browser may come up
with different solutions when a default IFS is encountered, and the default
IFS is not useful.

Typically, there is no situation where a scene author or factory would want
to use an IFS without vertices. However, automatic scene construction may
make it natural to first add a default IFS, and then modify it. This was
the case with d3.

Should we have renderable defaults for IFS and other composable geometries
? Why waste the opportunity ? It could be a triangle or square.

Spec. wise, I think a short statement that NULL coord values are ok but do
not render would be helpful.

Andreas



---on the phone---
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