How To: Create AutoCAD 3D Polylines from 3D ArcGIS Line Features
Instructions provided describe how to create AutoCAD 3D Polyline entities from 3D ArcGIS features using the extended functionality of the Export to CAD geoprocessing tool.
By default, Export to CAD creates planer 2D lightweight polylines where the elevation of the polyline is set to the elevation of the first vertex of the input feature. Lightweight polyline entities in AutoCAD do not have the ability to store vertices with varying elevations.
The default Microstation linear element that is created by Export to CAD already has 3D capability and therefore there is nothing more that is needed.
To create entities in AutoCAD that can include vertices of varying elevation: first include a field aliased, named, or renamed to 'CADType' in the output feature class. This allows the overriding of the default lightweight polyline CAD entity type that is created for linear features.
Populate the 'CADType' field with the value of '3D Polyline' for all features to create varying elevations.
When the 3D feature class is exported to AutoCAD using the Export to CAD tool, the value in the 'CADType' field is used to create an AutoCAD 3D Polyline entity, which has the ability to store verticies with varying elevations. The Export to CAD tool can use the 3D feature geometry to build 3D Polyline entities, including vertices that may have differing elevations within the same entity.