Lesson Note On Civil 3D Building a Surface

Building a Surface

To build a surface

1. Create a new surface if needed. For more information, 

2. Add surface data to the surface folders if you haven't already.

3. From the Terrain menu, choose Terrain Model Explorer.

4. Right-click on the surface folder, for example to display the shortcut menu.

5. Click Build to display the Build Surface dialog box.

6. Click the Surface tab if it is not already active.

7. In the Description box, you can type a description for the surface. The surface description can be up to 255 characters.

8. Select one or more of the following options to control how the surface is built:

• Log Errors to file: Select this check box to create a <surface name>.err file in the following folder:

c:\Land Projects <Version Number>\<project name>\dtm\<surface name>

This log file records the time it takes to build the surface, and records each step that the Build Surface command performs, such as adding point files or point groups to the surface.

• Build Watershed: Select this check box to build a watershed at the same time the surface is built. If you select this option, then be sure to click the Watershed tab and set up the watershed options.
• Compute Extended Statistics: Select this check box to generate extended surface statistics. These statistics are displayed when you click the surface name, for example in the Terrain Model Explorer.

9. Select any of the following surface data options to control how surface data is processed:

• Use point file data: Select this check box to build the surface using the data in the surface's folder. If you clear this check box, then the surface is built without the point file data.
• Use point group data: Select this check box to build the surface using the data in the surface's folder. If you clear this check box, then the surface is built without the point group data.
• Use DEM File data: Select this check box to build the surface using the DEM file data in the surface's folder. If you clear this check box, the surface is built without the DEM file data.

NOTE Building a surface using DEM files that contain large numbers of points can use significant system resources, especially if the "Build Watershed" check box is selected.

• Use breakline data: Select this check box to build the surface using the data in the surface's folder. If you clear this check box, then the surface is built without the breakline data.
• Convert proximity breaklines to standard: Select this check box to convert proximity breaklines to standard breaklines when the surface is built. Proximity breaklines obtain their exact point location and elevation by snapping to the nearest point on the surface. If you convert proximity breaklines to standard breaklines when building the surface, the breaklines are saved with fixed locations and elevations. Therefore, if any of the surface point data that the proximity breaklines were snapping to is subsequently changed, the breaklines are not updated with these changes.

When a proximity breakline is converted to a standard breakline, one or more standard breaklines are added to the breakline file in the Terrain Model Explorer, each with the description of the breakline from which it was converted.

Clear this check box if you want to preserve proximity breaklines when building the surface.

• Use contour data: Select this check box to build the surface using the data in the surface's folder. If you clear this check box, then the surface is built without the contour data.
• Minimize flat triangles resulting from contour data: When building a surface, select this check box to check each contour in the surface for any triangles that have three points at the same elevation. The program attempts to remove any such triangle by flipping faces. 
• Apply boundaries: Select this check box to build the surface using the data in the surface's folder. If you clear this check box, then the surface is built without the boundary data.
• Apply Edit History: Select this check box to apply the Edit History to the surface after it is built. The Edit History records all the surface editing that you have performed. For example, if you built a surface and edited it, but need to build it again, you do not have to make all the edits that you made previously. Just select the Apply Edit History check box and the edits repeat automatically.
• Don't add data with elevation less than: Select this check box to exclude any surface data that has an elevation less than the elevation you type in the box.
• Don't add data with elevation greater than: Select this check box to exclude any surface data that has an elevation greater than the elevation you type in the box.

10. If you selected the Build Watershed check box, then click the Watershed tab.

11. In the Minimum Depression Depth box, type the minimum depth at which a depression in the surface is to be considered a watershed. This setting prevents minor depression depths from being defined as watershed subareas.

12. In the Minimum Depression Area box, type the minimum area at which a depression in the surface is to be considered a watershed. This setting prevents minor depression areas from being defined as watershed subareas.

13. Select or clear the Must Exceed Both Minimum Area And Minimum Depth check box:

• Select this check box to create watershed subareas of only those depressions that exceed both the minimum area and the minimum depth.
• Clear this check box to create watershed subareas of those depressions that exceed either the minimum area or the minimum depth.

14. Click OK to build the surface.

A message dialog box is displayed, informing you that the program has finished building the surface.

15. Click OK.

16. If you want to view and edit the surface triangulation, then Import 3D Lines into the drawing.