Join Eric Chappell for an in-depth discussion in this video Understanding feature lines, part of AutoCAD Civil 3D: Site Design.
- [Instructor] Feature Lines are a fundamental building block of grading design for site projects. In this video we'll take a look at what Feature Lines are and how they behave. The first thing to know about a Feature Line is that it is simply a 3D linear path. In fact, I think you recognize that we're looking at in this drawing a parking lot. On the left view we're looking at a top down or plan view, you can see it represented in the view cube. And in the right side we're looking at a 3D isometric of the same parking lot.
The reason we don't see the paint striping in the 3D view is that it's way down at elevation zero, so it's well out of view. So if we take a closer look at this representation of a parking lot we see some red linear features, we see some orange features as well, and these happen to be Feature Lines. The red ones are a curb definition. So this is the edge of the gutter, the flow line, the top face, and the top back. So that's what Feature Lines do, they represent edges or linear objects in a three dimensional form in your drawing model.
In fact, if you're familiar with AutoCAD 3D polylines in a fundamental sense they're very similar. Now there are some things that are much better about Feature Lines and that's what I want to talk about next. For example, Feature Lines can have curves. If I take a look at this red line here you can see that it's got a nice, smooth curve to it, and it is truly an arc. The reason I'm so excited about that is because 3D polylines in AutoCAD can't do that. It's impossible to have a curve that starts at one elevation and ends at another.
The only way 3D polylines can pull that off is to segment the curve and turn it into lots of little straight lines. Feature Lines don't have that restriction. Another thing that's cool about Feature Lines is that they interact with each other. This green object is also a Feature Line and watch what happens when I make it cross the red Feature Lines. And you want to keep your eye on the 3D view on the right side. You can see how the red Feature Lines dipped down to match the elevation of the green Feature Line.
And that's just a simple example of that interaction between Feature Lines. We'll talk about that more in some upcoming videos. Feature Lines can have elevation points. If I zoom in and click on this Feature Line you'll notice some square grips that are colored a little differently than we're used to seeing with AutoCAD, but then we've got these strange circular grips. What are those? What do they have to do with? And these represent elevation points. They serve to provide an elevation data point only.
Only vertically, not horizontally. So these square grips are just like you're used to seeing with polylines and lines and circles and things like that, but the circle ones are special. In fact, if I try to move a circular grip I can only move it along the Feature Line, I can't change its position in the X, Y axis. That's a very powerful capability, because when we're doing grading design a lot of times we want to address the elevation, or the Z-axis, independently from the X and Y plane.
So that's an important difference. Another thing that's different is that Feature Lines have styles and names. If I right-click and go to Feature Line Properties you'll see that this has a Style assigned to it that tells it to act like a Curb and I can also apply a Name to my Feature Lines, which is handy when I use them in other places when I reference them in corridors, or when I build surfaces from them, or things like that. And another really important advantage or benefit of Feature Lines is that Civil 3D provides a whole set of specialized tools for editing them and you'll see them if I click a Feature Line we've got an entire ribbon just about dedicated to Feature Line editing.
A whole section on editing geometry or the X, Y plane, and then a whole section on editing elevations. And the tools are so powerful and specialized that we even see tools that run inside of the panorama. And here's a spreadsheet editor where I can go in and edit the elevations and slopes of the individual segments of the Feature Line. These commands that I just showed you do not have their full effectiveness on 3D polylines or regular lines or arcs, they are designed for modifying and working with and managing Feature Lines.
So it really gives you a lot of power to do the things that you need to do when you're grading the site. And most importantly, the main job of a Feature Line ultimately is to become a break line in a surface. So let me turn on the contours for the surface that is being driven by these Feature Lines. It's called Parking Lot with Daylighting, and I'm just going to go into Surface Properties, and assign a style that we can see. First, Contours.
So you can see the contours that are forming the parking lot. And actually we can see what we need to see with this style, because it displays contours in plan view and Tin lines or triangle edges in 3D view. And there you can see very distinctly that the Feature Lines in red and in orange that I see in plan view are driving and actually providing the data and controlling the formation and arrangement of the Tin lines in the surface.
So that's their important job when it's all said and done at the end of the design Feature Lines become break lines in a design surface, that's what they do. So there you have it, Feature Lines 101.
- What is site design?
- Creating feature lines
- Breaking, joining, trimming, and extending feature lines
- Adding and removing elevation points
- Raising and lowering feature lines
- Creating grading objects
- Building a grading scheme
- Creating curbs and parking lot surfaces
- Labeling a grading design
- Creating a storm design
- Adding inlets and pipes to a storm design