Ken wrote in message <36E34714.CA08E2BC@pacbell.net>...
> DXf has the ability to store either face or line info or both. Sometimes
>the program exporting the model will only export one or the other sometimes
>both. Conversion programs also have their own way to handle the data in the
>dxf file and it varies with who wrote it.


But does the face info include normals?  That is, is one "face" a plain
triangle (three points) or a smooth triangle (three points and three
normals, as in POV and OpenGL)?  For that matter, how do mesh-based editing
programs define such things?  I see a mesh of triangles, but how does it
know those approximate real surfaces?  Or are they just facets, period, and
it uses the joining angle idea like the import setting you told me about, to
smooth things implicitly (which would make it difficult to represent a sharp
edge that is below the critical angle!)

'learning,
--John

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