From the course: Autodesk Civil 3D 2022 Essential Training

Understand corridors - AutoCAD Civil 3D Tutorial

From the course: Autodesk Civil 3D 2022 Essential Training

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Understand corridors

- [Instructor] Corridors are used to model 3D linear features such as roads, ditches, dams, and many others. Before we dig into creating corridors let's learn a little bit about how they work. You spent the last four chapters working with alignments and profiles. And as you now know, and alignment represents the path of an object in the X, Y plane in 2D, and a profile represents the path of that object in the vertical axis, or all of the elevations are Z values. What happens when you create a corridor is that you combine the alignment and profile. So you combine the horizontal and vertical into a three-dimensional path, and then you insert what's called an assembly along that three-dimensional path. It sounds like magic, but let me show you how it works in this three-dimensional view on the right. You'll see if I zoom in closely we've got this dashed line here. This is something called a 3D chain and it's not something that many Civil 3D users know about, even the most experienced ones. And it is the result of an alignment and a profile coming together. Now, this is the one for the existing ground of our road. If we click down here, we'll see that there's one for the proposed road. Now, if you're following along and you're trying to click that and you're unable to, what you may need to do and I'll press escape here is select the corridor, right click, go to display order, and then send to back. You need to get that corridor behind the 3D chain. Once you do that, you should be able to click right here on the center line of the corridor and select that 3D chain. I'll right, click and pick object viewer. And it's not going to look like much but we can at least get an idea of what I'm talking about. If I orbit this around, you can see that it's this linear three-dimensional object that represents the path of the center line of our road. So that's actually most of what we need to build out our corridor. The last piece of the puzzle is this object that you see in the top right corner. This is called an assembly and it represents our proposed cross section for the road. And not only does it show the outer shape of the road, but it also contains some internal information as well. Now this is a very simple assembly for a more complex one for these lanes, you would actually see multiple layers representing the different strata for how the road is built out. And you might even see things like sub drains and there's all kinds of possibilities for the detail that can go into building out an assembly. But the important thing for our immediate purposes is that this assembly is defining the top and outer edges and even the underside of the shape of our road. And what happens when you build a corridor and you can see it right here is Civil 3D, after we define this assembly, it takes that assembly and inserts it at increments along this 3D chain. If I zoom in really close, you can see that the crown point of this assembly, this point right here, is perfectly inserted along that 3D chain here, and then here, and then along the way down through the corridor. So it builds kind of like a framework, like the frame of a ship. And then with an object, like a surface we can stretch the skin over that frame to build out the rest of the corridor. And that's actually what you see here. These criss-cross lines are a surface that represent the full filled in three dimensions of our corridor. So the basic anatomy of a corridor is this, an alignment and a profile come together to form a 3D chain and then an assembly is defined and inserted again and again along that 3D chain to build out the shape of the corridor. So now you've just learned the anatomy of a corridor. Let's jump into the next video and begin by building an assembly.

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