I had done this lisp to draw a section line on a DTM (3Dfaces), creates a 3Dpoly on 3Dfaces.I think this is not the corect solution.
Use 3Dfaces nonoverlapping.
Not very nice, but it works ... :-)
Only applicable on Stefan's example DWG when folded and unfolded 3DFACES are exact match - so this is no good for unfolding : http://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/3d-faces-down-to-zero-level/m-p/5878805/highlight/true#M336186
I would like to comment on an error in the lisp PROF_3DF_EN.LSP
The 3d polyline is not well projected.
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Use 3Dfaces nonoverlapping.
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