October 2016

Have you ever had two surfaces that you needed to combine together but the problem is, at the boundary of the inner surface, its elevations don’t match the elevations of the outer surface. In cases like this, if you paste them together you can get some really odd things going on where they are supposed to meet.

An example of this might be that you have one surface that was created from USGS data and another surface that was surveyed. They should be close to the same elevations but they won’t be exact. I often have people ask me if there’s a way to combine them but use a buffer between. Using a buffer you won’t get those almost vertical triangles or triangles that go out for quite a while until they connect into the other surface.


Pasting Surfaces Issue

In the above image, I have two surfaces, one with green triangles and a yellow border and one with grey contours. I need to paste them together to create a combined surface. Any surface points that are under the border of the inner surface when it’s pasted in will be removed and that white, thick line represents the triangles from the outer surface that are unchanged. As you can see, there are some odd things going on.

Since there’s no way to add a buffer when pasting surfaces, what do you do? Well, here’s how you do it in five simple steps:

  1. Extract the border of the inner surface.
  2. Offset this extracted border the buffer distance.
  3. Assign the elevations from the outer surface to this new object.
  4. Create a surface from this offset.
  5. Paste all three surfaces together.

1. Extract the border of the inner surface.

You probably already know how to do this but, in case you don’t, it’s pretty simple. Just follow these steps:

  • Make sure the surface you want to extract the border from is using a style that actually displays the border (you can’t extract something if the surface isn’t dislaying it).
  • Select the surface and on the ribbon expand out “Extract from Surface” and choose “Extract Objects”.


    Extract Objects

  • Select “Border” from the options in the next dialog box (deselect anything else you don’t want to extract from your surface) and click OK.


    Select the Border to Extract

You now have a 3D polyline in your drawing where the border of the surface is.

2. Offset this extracted border the buffer distance

Again, pretty simple but I’ll explain the steps here. On the Modify tab of the ribbon, on Edit Geometry panel, there’s a command called, “Stepped Offset”.


Stepped Offset

Follow the command line prompts and offset it the distance you need. When it comes to setting the elevation, it really doesn’t matter what you choose as we’ll set the elevation of this new polyline in the next step. The AutoCAD Offset command most likely will not work as this is likely to be a 3D Polyline and the Offset command only works on 2D objects.


Offset Polyline


3. Assign the elevations from the outer surface to this new object

This new polyline needs the elevations of the outer surface. Still on the Modify tab of the Ribbon, on the Edit Elevations panel, there is a command called, “Elevations from Surface”.


Elevations from Surface

Run this command and select the polyline. Next you’ll see a new dialog box asking you which surface to use. Select the outer surface (in this example it’s called “Pre-EG”) and make sure you toggle ON the option for, “Insert intermediate grade break points”.


Elevations from Surface Options

Your new 3D polyline now follows the outer surface exactly and we’re ready for the next step.

4. Create a surface from this object.

Again, pretty simple but here are the steps.

  1. On the Home tab of the ribbon, on the Create Ground Data panel, expand out Surfaces, and select the first option, “Create Surface”.
  2. Name it appropriately (I would call it something like “<inner surface name> Pasting Buffer”. Set any other settings you want (the style really doesn’t matter – I would probably choose something like, “No Display” if it’s an option).
  3. On the prospector, expand out the new surface, expand out the definition, right click on Breaklines and chose, “Add”. Select the offset 3d polyline and apply the breakline settings as desired.

And that’s it. You’re done.

5. Paste all three surfaces together.

Now, that you have done all that, we are ready to paste them all together. You can past them into the original outside surface but I’m not a fan of that. I would much rather have the outside surface remain intact in case I need to use it for something else. I typically will create a new surface (see step four for the steps to create a new surface).

On the Prospector tab, expand out the new surface, expand out definitions, and choose “Paste”. Select the surfaces you want to paste in. The order you paste them in is very important as whatever is within the border of the incoming surface will completely overwrite everything inside it. The order we will use here is 1) Outside surface 2) Buffer surface 3) Inner surface.


Paste Order

The following sequence of images show the progression of the new surface as the other three surfaces are pasted in. I left in the thick white line from earlier as a reference.


Outer Surface Pasted In


Buffer Surface Pasted In


Inner Surface Pasted In

As you can see, that buffer works very nicely. You can compare this to a surface that only has the outer and inner surfaces pasted in.


Same surface without the buffer surface

What do you think? Is this something you might use? Leave a comment if you do this a different way. I always love to hear about different ways of accomplishing things!

The data set I used is from the training manual “A Practical Guide to Civil 3D 2017” by Rick Elis. You can order a copy from his company CADapult if you would like one. This is the book I use in my classes.


If you’ve downloaded the Civil 3D 2017 v1 Enhancements and tried using the Swap Pressure Network Parts command, you might have seen some odd things happening…


Shifting Parts When Swapping Parts (picture from Autodesk)

Autodesk has released a hotfix for this. It’s a simple fix, just download a file and swap out the one on your system with the new file. The hotfix can be found HERE.

A few weeks ago, the Civil 3D product team released some new functionality for Civil 3D 2017 and they called it the “AutoCAD Civil 3D v1 Enhancements”. You can read the official documentation HERE. Don’t be too worried about what it’s called, it’s basically the same thing we had back in 2016 and earlier called Productivity Packs.

Not all the tools that are part of the v1 Enhancements are new, some of them are the tools that are traditionally available via the productivity packs (such as the Autodesk Civil Engineering Data Translator, the rail Turnouts and Crossings, and the Traverse, Input, Edit, and Adjustments. There are, however, some new tools that I will discuss here. In the following image, you can see all the tools that are available:


Available Tools in the v1 Enhancements

Probably the easiest way to download the tools (provided you have the permissions to install on your system) just use the Autodesk Desktop Manager. Most likely it will be running in your Windows taskbar (you know, the bottom right of your screen). You can launch it from there, or from the Windows Start Menu. If you need to download them so you can add them to a deployment or install them on multiple computers, you can find them HERE.


Autodesk Desktop Manager

If you are looking to download it (so you can deploy it to your organization for example), you can go to manage.autodesk.com and download it there. It can be found under Updates.


AutoCAD Civil 3D 2017 v1 Enhancements



In Civil 3D 2016, we could add custom properties to any object in Civil 3D that we wanted (you can read about how to do that HERE). 2017 added a button on the ribbon to assist with this (woohoo) but there wasn’t much we could do with those properties. In the 2017 v1 enhancements, we can now add that data to our labels! Now that’s progress!


Property Sets Data in Labels

Analyze Gravity Network

We’ve been able to compute runoff and flow in pipes for a long time with Civil 3D but we’ve always had to leave the program and open another (i.e. Storm and Sanitary Analysis or Storm Sewers). In the v1 Enhancements, there are now tools to run a simple analysis directly within Civil 3D.

The Analyze Gravity Network command now allows you to run a HEC-22 Analysis directly in Civil 3D with your pipe network. You’ll need to create catchments and assign them to the appropriate structures and then run the command. Choose the IDF curve, set the properties of the parts in the network, and then review the results.

Analyze Gravity Network

Swap Pressure Network Parts

Introduced in Civil 3D 2013, Pressure Networks have been an options for everyone needing to model water distribution or other pressure networks. One of the drawbacks (and very frustrating things) is if you put in pipes of the wrong size, there was no way to change them to a new size, the only option was to erase them and recreate them. With the v1 enhancements, that all changes.

After running the command, simply select the parts you want to swap to a new size (pipes, fittings, and appurtenances). Choose the new size and what elevation you want to preserve (crown, invert, center, etc.) and it swaps them out for you!


Swap Pressure Network Parts

Wrap Up

So, what is your favorite part of the v1 enhancements? Was there something I missed? Something Autodesk missed? Feel free to comment and let the world know what you think!