Exporting a TIN Surface .DWG to a .DXF in Civil 3D

This workflow will outline the steps required to export a .DWG file that contains a TIN surface to a .DXF file for upload into the Propeller Platform. This workflow applies to projects with a design or finish grade TIN surfaces in Civil 3D. 

Civil 3D Workflow

Open Civil 3D 2020 Imperial. Open the existing .DWG file containing the TIN surface. The drawing should already be georeferenced, in the proper coordinate system, and set to the correct units.

Once the drawing is opened, ensure you are in the model space and select the TIN surface.

Right-click and select Edit Surface Style. The Surface Style dialog box will pop up.


Navigate to the Display tab. You will see a list of items associated with the TIN surface style. They can be turned on or off to modify what objects associated with the TIN surface are displayed in model space. 

The light bulbs under the visible column indicate which surface attributes are turned on or off for display in model space. Turn off all surface style attributes except for the triangles. Below is a “before and after” of the TIN surface display style modification.

Civil3D_Contours_and_Borders.png Civil3D_TrianglesOnly.png
Before: Contours and border After: Triangles only


After modifying the surface display style to show only triangles, select the TIN surface and type the command “explode.” This converts the TIN surface to a Block Reference. 

Select the TIN Block Reference and type the "explode" command again. This will convert the Block Reference to individual 3D faces, which the Propeller Portal can interpret. 

You are now ready to export the TIN surface, which has been converted to individual 3D faces, to a .DXF file. 

Exporting the TIN Surface .DWG to a .DXF 

Click on the Civil 3D icon in the top-left corner of the screen.


The Civil 3D dropdown menu will appear. 

Expand the Save As menu by clicking the black arrow to its right, and then select Other Formats.


The Save Drawing As dialog box will appear. Set the Files of Type to AutoCAD 2018 DXF (*.dxf). Navigate to the desired folder location.

Click the Tools dropdown menu in the top-right corner of the dialog box. Select Options. The Save as Options dialog box will appear. 

Select the DXF Options tab and check the Select Objects box. The format should be ASCII, as shown below. Click OK to return to the Save Drawing As dialog box. 

Click Save

Note: The .DXF has not yet been created. You will need to select the objects you want to export with the .DXF.

After clicking Save, your cursor will change to a box with the text “Select Objects” next to it.

Make a selection box by clicking just outside the bottom right corner of your surface and drag to just outside the top left corner of your surface to select the entire TIN surface. Once all 3D faces have been selected press Enter.

After pressing Enter, the .DXF file with the TIN 3D faces will be exported to the selected folder and is ready to be uploaded to the Propeller Platform.

I still can't do it!

We wrote these articles to equip you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient. 

If you're stuck, you can connect with our support team by clicking the support button on the top right corner of your user portal.