Extracting CAD Layers

I am trying to extract curves from an AutoCAD file but am running into an issue with Empty Lists. I have an example of a Linked and Imported CAD file in my Revit document. I am trying to pull a single CAD layer (J-Floor) which I can see in Revit, CAD.LayerNames shows it, but it does not show in CAD.LayerNamesInUse nor can I exctract the curves via CAD.CurvesFromCADLayers

I seem to remember reading somewhere that there is an issue with 3D lines?

I have reviewed the following links but with no success.

Revit 2018
Dynamo 1.3.2
bimorphNodes 2.2.70


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Hi @BenDoty_LMN

Could you drop dwg file here?

Here is the CAD file. I think it is pretty well cleaned.

2018_0326 MINT Export.dwg (1.7 MB)


Hi @BenDoty_LMN the problem is caused by the elements in your DWG; they import as meshes which means the CurveFromCADLayers node has nothing to convert. In theory, it’s possible to extract the boundaries of a mesh, however the last time I looked at this there was no simple way to know which vertices we’re connected by an edge (which can then be converted to a Proto curve) and which vertices were unrelated and not connected by an edge - like what results in your file as a consequence of the separated profiles - so meshes remain unsupported by the node.

The simplest solution is to either explode your polygons in AutoCad before linking/importing the DWG into Revit or convert them to polylines, both of which should convert without issue. 3D lines are supported too, but only within the limits of the Autodesk ShapeManager (so non-planar curves are flattened to the plane for example).

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@Thomas_Mahon Thanks for the input. I will check out the original CAD file and see what I can do. Cheers!

@BenDoty_LMN You see how it helps others to find the issue if anyone drop relevant files. Thanks to @Thomas_Mahon for pointing out. This is how we can extract boundaries from Mesh:


Thanks for the alternative solution @Kulkul
I’m aware it’s possible - I was speaking specifically about limitations of meshes extracted from DWGs in the Revit API context, where such a solution isn’t possible (no mesh toolkit)!