A short answer is that local coordinates (location of each vertex) are specific to each model/object. Global coordinates express the location in the 3D world of your model/object.
This short answer probably isn't very helpful, however, if you're new to 3D.
If you could provide some context/information as to what you're looking for or trying to do, perhaps we could provide more assistance.
If it helps, where AC3D is concerned, at least with the later versions, all coordinates are expressed in global coordinates. Inivis could verify this, but I'm fairly certain this is the case.
Dennis
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