Simplifying a TIN Surface in Civil 3D

Civil 3D Workflow

Open Civil 3D 2020 Imperial. Open the existing .DWG containing the TIN surface.  You should have already georeferenced the drawing in the proper coordinate system and set it to the correct units (US Survey Feet).

Once the drawing is opened, ensure you are in model space with the TIN surface in view.

Locate the TIN Surface under the Prospector tab of the Toolspace.

Right-click the surface name and select Surface Properties.

Navigate to the Statistics tab of the Surface Properties dialog box.

Expand the TIN category to see the number of triangles the TIN surface contains.

Once you’ve verified the number of triangles, click OK to close out of the Surface Properties dialog box. 

Navigate back to the TIN surface under the Prospector tab of the Toolspace.

Click on the small plus sign to the left of the surface name to expand the surface attributes.

Click on the small plus sign to the left of Definitions to expand the list of items that can be added to the surface and tools used to edit the surface. 

Underneath Definitions, right-click Edits. Then, select Simplify Surface.

Select the Edge Contraction method and click Next.

Next, click Region Options. This should default to the first choice: Use existing surface border. Make sure this option is selected and click Next.

Once you’ve specified the region, the next step is to specify the Reduction Options. The reduction options using the Edge Contraction method involve setting a percentage of points to remove. A good practice is to start with a small percentage, such as 5%. 

Click the checkbox next to Percentage of points to remove. You can use the slider to adjust the percentage or type it in the box next to the slider.

Click Apply, then click Finish.

Repeat the steps to view your Surface Properties from the Prospector tab in the Toolspace. You can also click on your surface in model space to select it, then right-click and select Surface Properties.

Expand the TIN category under the Statistics tab to view the number of triangles on your surface. It should have decreased from the previous number.

If you are satisfied with the new number of triangles in your surface, click OK and save your drawing. You are now ready to export your TIN surface to a .DXF file for upload to the Propeller Platform

If the number of triangles is not reduced enough, navigate to your surface in the Prospector tab of the Toolspace. Click Edits under the surface Definition. A list of edits should appear below the Toolspace palette.

Select the Simplify Surface edit, right-click it, and select Delete. This will return the surface to its original design. It is common practice to avoid simplifying an already simplified surface to maintain the integrity of the surface. 

Repeat the workflow for simplifying your surface and try a larger percentage of points to remove. Once you’re satisfied with the reduction of triangles, export your TIN surface to a .DXF file for upload to the Propeller Platform. 

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