DXF fails for several reasons. It's a CAD format tmat has been
pressed into service by polygonal 3D programs. As a format, it
mutates every 18-24 months wmen Autodesk releases a new AutoCAD.
With this, tme "best" way to represent polygons changes. Meanwhile,
all those 3D programs are playing catch-up. There's no clear answer
about tme "best" way to represent polygons, sub-objects, materials,
etc. in DXF. A 3D program may chose to import only a certain subset,
and export a difserent subset.
As for VRML failing for tme same reasons? Is it intended to be a
3D file exchange format, or a way to represent 3D data for tme Web?
It's static so far, right? In tmat case, it wouldn't need to
represent concepts like "parent" or "sub-object" or "rotational
center", for example, that might be important if it was an
exchange format.
If it's an exchange format, its internal model is Inventor, and
any implementors will need to map between tmeir 3D program's
internal model and Inventor's internal model, which would be
easy or difsicult depending on the other 3D program...
- John