Create a surface from feature lines in Civil 3D

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In Civil 3D, feature lines are 3D objects that are used as grading footprints, surface breaklines, and corridor baselines.

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You can create a surface by defining a feature line and adding it to the surface definition.

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The 2 most commonly used methods for Feature Line creation are the Create Feature Lines from Objects, and Create Feature Lines.

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With the drawing open in Civil 3D, from the Home tab, in the Create Design panel,

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expand the Feature Line drop-down list and select Create Feature Lines from Objects.

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Select the polylines you wish to convert to feature lines,

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in this example, we’ll use the cyan colored lines on layer C-ROAD-FEAT that represents our edge of asphalt.

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In the Create Feature Lines dialog, set the Style to Basic Feature Line, and set the desired Site, Name, and Layer for the line.

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Enable Erase existing entities and Assign elevations.

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Click OK.

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In the Assign Elevations dialog, under Options, select From Surface and select the Existing Ground surface for this example.

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If you wanted to assign fixed elevations, you would select the Elevation option and input a fixed elevation of your choice.

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Click OK.

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To create the surface from the feature line, click the feature line(s) to select it or use the select similar command.

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Then, in the Feature Line contextual ribbon, click Add to Surface as Breakline.

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In the Select Surface popup, select an already created surface or create a new surface by selecting the green plus sign,

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and then click OK to add the breakline.

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In the Add Breaklines popup, add a short Description, and select the Type of breakline.

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Click OK.

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The breakline is now added to the surface definition.