> Can GML express multiple instances of geometry?
Anselm,
Yes, it can. Few have accused GML if not providing enough options.
> I would like to express a city building and have multiple instances of that
> building at different orientations and positions.
Well, I'm not sure exactly what you mean here.
Clarifying this is important to me because I feel it points out
problems in the OGC. The limits in the grammars they invent are
affecting how people think.
In VRML one can describe a geometry and then place more than one copy
of that geometry at different places in the 3 dimensional space.
Here is an example:
http://www.cg.tuwien.ac.at/studentwork/VRSem96/VRML/vrml6.html#stool
And here is another example:
DEF Skyscraper Shape {
appearance Appearance { material Material {} }
geometry Box { size 3 4 5 }
}
Transform {
translation 1 2 3
children USE Skyscraper
}
Transform {
translation 4 5 6
children USE Skyscraper
}
I cannot find a similar concept in the core GML profile.
I don't see this as a small defect.
As humans the challenge we face when trying to communicate is that
reality is continuous. We can each perceive the world in different
ways. We often invent grammars to cleave problem spaces into
manageable pieces for sharing. Features we think others observe such
as "similarity" and "abstraction" help define "understanding".
That I don't see multiple instancing in GML has always surprised me
and is one of the reasons I've down-scored the OGC as a successful
standards body.
I'd like to be proven wrong on this. It makes no sense to me and it
feels more like I must be missing something.
- a
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