Vexed by 3D Polylines?

3D Polylines can be quite useful, but sometimes you might find them in a map and struggle to use them as 2D boundaries, wishing there was a simple way to convert them to flat polylines.

The Drawing Cleanup dialog box in Map 3D and Civil 3D offers a solution.  This tool is available from the Tools tab of the ribbon in both geospatial workspaces. It is also available from the Edit Object tab tabs in the Task-based Geospatial WorkspaceMap Classic users will find it in the Tools section of the Map pull-down menu.

To use the AutoCAD Map 3D Drawing Cleanup tools to convert 3D Polylines to Polylines:
  1. From the Select Objects step of the dialog box, you can choose whether to perform the conversion on all objects, or you can select them individually or by layer.
  2. Choose one of those methods to select the 3D Polylines you want to convert.  It is probably wise to select the objects manually (or by layer) unless you are certain there are not any 3D Polylines that need to retain the Z-values in their vertices.


3.  Click the Next > button and ignore the Cleanup Actions step. All conversions are Automatic, and are controlled in the Cleanup Methodsstep.

4.  Click the Next > button again to proceed to the Cleanup Methods step.


5.  In the Cleanup Methods section, you can choose whether to modify the original object, or retain the original and create new objects.

You can also choose whether to put these new objects on a new layer, which is a wise move if you are uncertain whether the 3D Polylines will be needed again later.

6.  In the Convert Selected Objects section, enable the 3D Polyline to Polyline option.

7.  Click the Finish button.

All of the selected 3D Polylines are instantly converted to Polylines.  Their elevations will be whatever the “Z-value” was on the FIRST vertex of the 3D Polyline.  For instance, if you had a 3D Polyline that was drawn from “10,10,10” to “20,20,20”, then all of the vertices of the the newly created polyline will be at elevation 10.  The X and Y coordinates of each vertex will be unchanged.

The Drawing Cleanup tool can also convert:

•    Lines to Polylines

•    Arcs to Polylines, and

•    Circles to Polylines or Arcs

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