Join Josh Modglin for an in-depth discussion in this video Creating surfaces: Boundary definition, part of AutoCAD Civil 3D Essential Training.
- [Narrator] Now as the software goes through using the algorithm to connect the points, it may connect points using triangles that really are stretching beyond or even going across in such a way that it interpolates inaccurate data. And so what we are going to do is we are going to delete triangles using boundaries. We're going to establish boundaries for our surface. So let's go ahead and open up our boundary exercise file. 0404 surface boundary.
We see a few different green poly lines here. We have one here, we as well have this one. This is the current boundary of the surface. Now if we start looking, you see the triangles. The triangles are crossing here, but this is the last known survey point, last known survey point. So all of this informaiton is inaccurate. Same here. Survey point, survey point, survey point, all of these contours are inaccurate because the triangle came across here.
Of course that became part of the model, so these triangles really need to go away. And so what we're going to do is we are going to add a boundary and control or delete triangles in such a way that we get the accurate data of what was truly shot in the field without creating any type of misplaced interpolation. So I'm going to go to my surface again, under existing grade, the definition of the surface, and we are going to choose boundaries. I'm going to right click and choose to add a boundary.
Now we are going to add an outer boundary. There's a few different types of boundaries. We are going to look through some of these together, so let's just focus on the outer. One of the big, key factors is whether or not to create a nondestructive break line. So what I'm going to do is I'm going to go ahead and not create a nondestructive, so in other words, we're going to be destructive. And I'm going to click okay, and before I select this outer poly line, I want to explain what that is. If we say nondestructive, anytime a triangle crosses that boundary, what it will do is it will add a new point to the surface.
The point will be based on the triangles at segment It's interpolated elevation at that point. So we're adding information to the surface that's inaccurate. What we want to do is we want to destroy all triangles back to correct survey data. Back to correct survey data. And you see that my poly line is not exactly accurate. It's not sitting right on top of the triangles or on top of the points that were shot. All I have to do is make sure the poly line is far enough in to get rid of the triangles that are inaccurate.
So I go ahead and select this outer boundary, this poly line, and now you see nondestructive removed everything, not just touching, but all the way back to the last known good shot from the information that it has. Well let's go ahead and add another type of boundary. We're going to add a hide boundary. Hide boundaries may be useful when we're dealing with trying to hide information. Often times this comes into play when information wasn't able to be shot accurately inside this boundary like a donut, or a lot of times it's also used for buildings.
So you may shoot around the building outside edge, but the general practice is not to show contours or information through the building. In this case, we're going to choose nondestructive and click OK. Now notice again what I mentioned here is I was going to add a new point to the surface every location where these triangles cross. That's a lot of new points. Go ahead and select this rectangle and press OK. And notice everything's been removed from inside there.
And if you look at the surface now, you have many more triangles. All of the triangles are connected right along the edge. So points were added to do that and keep the information and the contours accurate as they were before we added the boundary. So everything on the outside is exactly as it was. So there's a big hole now. And when I say hole, it's not just contours, it's not just triangles, it's truly a hole in our model.
There's one more boundary we are going to add. I'm going to right click and choose add. That boundary is what is called a show boundary. Now obviously you can't have a show boundary without a high boundary. But lets' say there is a court yard situation, or better yet, there's an island and the water and the elevation and the depth of the water wasn't shot. You sat along the edge of the water and then you went and shot the island. Again, choose nondestructive. Click OK, now we're going to select this inner rectangle.
And so it was smart enough to remember all of the data we had before including the break lines that we added, and then it added additional points along that rectangle because we chose nondestructive. So everything is very accurate now, let's go ahead and using our layer control, I'm going to freeze the ten lines and we can more accurately see now these contours and that they've come in exactly as they were. And again, if we look at this in 3D, we now have a hole and the inner portion is filled in, all controlled by different boundaries.
We added an outer boundary, we added a hide boundary, and then a show boundary inside our hide boundary. So boundaries really control where the triangles are and better yet, removes triangles where we don't want them.
This course gets you up and running with AutoCAD Civil 3D. First, instructor Josh Modglin shows how to model a surface, lay out parcels, and design geometry, including the making of horizontal alignments and vertical profiles. Next, Josh demonstrates how to create corridors, cross sections, pipe networks, and pressure networks. Then, he covers working with feature lines and grading objects, and how to share your data. He wraps up by providing an overview of plan production tools.
- Navigating the Civil 3D interface
- Using point groups and description keys
- Importing survey data
- Managing figures
- Creating and analyzing surfaces
- Creating parcels
- Working with alignments
- Working with profiles and profile views
- Working with assemblies and subassemblies
- Creating Basic and Advanced Corridors
- Using an Intersection Object
- Making sample lines, cross sections, and section views
- Creating a pipe network
- Understanding pressure parts
- Creating and editing feature lines
- Creating and editing grading objects
- Sharing and referencing data
Skill Level Beginner
Some of the exercise files do not properly function.
This course was built to work with the latest release of AutoCAD Civil 3D. If you are not running AutoCAD Civil 3D 2018 there are some exercise files that will not work for you.