User’s Guide

Surface Stitcher
User’s Guide



Surface Stitcher is an AutoCAD Civil 3D extension application which allows you to:

  • Smoothly blend two surfaces together
    • Calculate smooth infill for gap regions between surfaces
    • Calculate transitions across overlap regions
  • Use Smart Paste to:
    • Paste two surfaces together with offset transition areas with smooth infills
    • Paste a surface containing a hide boundary into second surface without obliterating the geometry of the second surface within the pasted void area.

Getting Started…


Surface Stitcher can run on any 64-bit Windows machine which can run a compatible version of AutoCAD Civil 3D. No 32-bit version is available at this time.


Surface Stitcher is intended to be loaded into AutoCAD Civil 3D as a plug-in using the AppAutoLoader feature introduced in AutoCAD 2012. The application files are automatically installed to the following location:

C:\Program Files\Autodesk\ApplicationPlugins

Note that installation of Surface Stitcher REQUIRES administrative permissions as it installs for ‘all users’.

Activating Your License

After installing Surface Stitcher, you will need to activate your license before you can run the application. You may need administrative privileges in order to complete this process.

To Activate:

1) Run AutoCAD Civil 3D and open a drawing (or start a new one)

2) Look for and select the ‘civil+plus’ ribbon tab at the top of the AutoCAD Civil 3D window

3) Click on either of the Surface Stitcher icons found in the ‘Surface Stitcher’ ribbon panel
Surface Stitcher Ribbon Panel

4) This will bring up the activation dialog box:

License Activation Dialog

5) In your purchase documentation emails, you should have received an activation key code…enter this in the field provided here.  If activating a new installation that is to connect to an existing network license, you can leave this field blank and proceed to ‘Advanced Options’ (below).

6) If installing a standalone license, click ‘Activate Now’ to proceed with activation.  Note that if you are using a proxy or are attempting to configure a network license, you will need to turn on the ‘Advanced Options’ using the button provided.

Advanced Options

If you enable the ‘Advanced Options’ feature, the ‘Activate Now’ button on the main activation dialog will change to a ‘Next…’ button.  Either click on this or select the ‘advanced…’ tab manually.  In this dialog you may:

  • Set the ‘License Mode’ (Standalone or Network)
  • Set the path to the network license file share
  • Manually activate your license with a code provided by tech support if you are unable to connect to the license server/activate automatically.
  • Enable the ‘Connect using a proxy’ option (if you enable this you will be provided an opportunity to set your proxy configuration settings).

License Activation Dialog - Advanced Tab

User Interface and Workflow

The Surface Stitcher commands are accessible via the Surface Stitcher ribbon panel found in the civil+plus ribbon bar:

Surface Stitcher Ribbon Panel

These features may also be invoked directly via the AutoCAD Civil 3D command line:

ACAD Command Line

Join surfaces

The Join Surfaces feature enables you to smoothly blend two surfaces together across both gaps and overlaps. Gap regions may be resolved using either a ‘smooth blend’ or a ‘planar’ method for calculating infill; overlap regions may be resolved by using one of the following methods: ‘smooth blend’, ‘average point elevations’, ‘top point elevations’, ‘bottom point elevations’, or ‘weighted average point elevations’. Transitional area data is calculated at grid points at a spacing controlled by the ‘Filler grid spacing’ setting, and the maximum gap distance that will be filled on the outside edges of the blend is controlled by the ‘Maximum outer fill distance’ setting.

The result of running this command will be a new surface in your DWG which contains the geometry of both source surfaces plus the calculated transition region geometry. The name of the new surface will by automatically set using the template ‘<Surface A> + <Surface B>’; the style of the new surface will be the default style for new surfaces.

Calculating Infill across Gaps

Surface Stitcher - Join Surfaces - Infill OptionsA gap region occurs where the two surfaces to be joined do not quite meet up.

Infill is calculated across gap regions using one of the following methods:

  • Smooth Blend: Calculates a smoothly curved surface to transition from one surface to another across the gap. This method is useful when the surfaces bounding the gap contain relatively large amounts of variation in slope and elevation along the edges of the gap region.
  • Planar: Calculates a simple triangulation which connects points across the gap using straight lines. This method is useful when the surfaces bounding the gap contain relatively little variation in slope along the edges of the gap region (i.e. where the surfaces contain mostly planar areas).

Intermediate data points are calculated within the infill on a ‘grid’; grid spacing is controlled by the ‘Filler grid spacing’ setting. The distance specified for this setting is in drawing units.

For the outer-most regions of the joined area we must apply a limit which tells Surface Stitcher to stop calculating additional infill, else we will end up with extraneous infill data which will have to be hidden via an outer boundary (much like triangulation along a concave edge of a surface). This is controlled by the ‘Maximum outer fill distance’ setting. For the outside-most regions only, once no more points along the edge of one surface fall within the specified distance of the other surface, the calculation stops and an outer edge is formed. The distance specified for this setting is in drawing units.

Calculating Transitions across Overlaps

Surface Stitcher - Join Surfaces - Overlap Options

Transitions in overlapped regions are calculated using one of the following methods:

  • Smooth Blend: This method treats the overlap region as if it were a ‘gap’. It ignores all elevation data within the overlap and calculates a smooth infill from the region boundary.
  • Average Point Elevations: This method will calculate new elevations for the transition using the average of both surface elevations for each common {x,y} within the region.
  • Top Point Elevations: This method will hold the ‘top-most’ elevations across the region.
  • Bottom Point Elevations: This method will hold the ‘bottom-most’ elevations across the region.
  • Weighted Average Point Elevations: This method is similar to the ‘Average Point Elevations’ method above, except that the averages are weighted such that the closer the point is to the boundary of a surface, the less that surface will influence the elevation. This results in a gradual, natural transition between the two surfaces.


The behavior of the ‘top’ and ‘bottom’ point elevation methods is illustrated below:

Overlap Resolution by top-most/bottom-most methods

The two surfaces being merged are represented as the teal and violet lines. The black dashed lines represent the limits of the overlap region. The green dotted line is a merged surface which uses the ‘top point elevation’ method, and the yellow dotted line is a merged surface using the ‘bottom point elevation’ method.

The averaging methods allow you to calculate a transition between the two surfaces as illustrated below:

Overlap resolution by averaging methods

The green dotted line represents a simple average whereas the yellow dotted line represents a weighted average. If the surfaces differ significantly in elevation, the non-weighted, simple average will result in a ‘step’ being created in the final merged model; the weighted average method avoids this and provides a natural transition from one surface to another. This natural transition is apparent if you look at the contours generated across an overlap transition calculated with this method:

Contours showing result of weighted average blending

The salmon colored contours are from the final merged surface. The gray contours are from the original surfaces (‘A’ on the left; ‘B’ on the right). Note that within the overlap region (between the green boundary lines), the new surface contour matches the adjacent surface contour at each edge of the overlap region boundary.

Smart Paste

Smart Paste is a new technology created for Surface Stitcher which allows you to ‘paste’ one AutoCAD Civil 3D surface into another, optionally using an offset boundary for transitions, and optionally preserving original ground data within regions where the pasted surface contains a void (hide boundary).

surfaces for Smart Paste

When we perform the Smart Paste operation, an intermediate ‘blend surface’ is created which contains the data to be pasted into either the targeted surface model or a new surface containing a pasted copy of the targeted surface model. Target surface data is optionally added back into the result surface within any pasted hide boundaries:

intermediate result surface ('blended surface')

This intermediate surface is then pasted into the target surface, yielding the final result:

final result surface

By comparison, if we were to simply paste the grading surface used in the above example into a copy of the existing ground, the area within the hide boundary at the center of the grading surface would be empty.

Note that because the target surface will ultimately end up containing the pasted data, you do not typically want to paste data into your existing ground surface directly, especially if that data is dependent on the existing ground surface (e.g. grading, corridor surfaces, etc.). Instead, create a new surface to contain the final result and paste the existing ground data into it first, then use it as the target instead of existing ground. This way, your existing ground data will be preserved, no circular dependencies will be created, and the final object dependencies will look similar to this:


Also, note that the Smart Paste process can take a fair amount of time to process once initiated. The larger/more complex your surfaces, the more time it will take to perform the necessary internal calculations and operations.


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