From the course: Cert Prep Autodesk Certified Professional: Civil 3D for Infrastructure Design

Create feature lines - AutoCAD Civil 3D Tutorial

From the course: Cert Prep Autodesk Certified Professional: Civil 3D for Infrastructure Design

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Create feature lines

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- [Instructor] Grading is the term used for shaping the terrain to represent the finished ground of a project. Let's take a look at feature lines, a powerful tool for shaping terrain. There are several ways to create feature lines. And to see them, I'll go up here to the feature line, drop down on the home ribbon tab. The first one is simply called create feature line. Let's give that one a try. I launch the command, select some default settings like the site and the style that I want to use and the layer. I'll click OK. And then I'm prompted for my first point. So I'll click a point here near the road and you'll notice that I'm prompted for an elevation. This command is kind of like drawing a polyline in AutoCAD except that for each point I select, I'm going to be asked for an elevation as well. So for this first point, I can either type in the elevation directly or I can derive it from a surface. So let's try that out. I'll click surface to use the surface option, select EG as the surface that I want to base it on, and I'll click OK. Let's pick another point. Here, you see the same behavior where I'm prompted for an elevation but I have a lot of different ways of providing or calculating that elevation. You'll notice right now, the default is specify elevation difference. But I can choose from difference, grade, slope, elevation, surface, or transition. I'm going to start with the grade option. Click that, and I'll type in the number two to indicate a 2% grade uphill. And if you watch over on this side of the screen, I'm actually looking at is 3D view of the same area as I'm looking at here. You'll see that segment of the feature line drawn. Let's pick another point. And this time, we'll do slope. So I'll click slope and I'll enter a three to indicate a three to one slope upward. And you can see the new segment that's been created. We'll pick another point. And this time, we'll use difference. I'll click the difference option and I'll enter 10 indicating that I want this point to be 10 feet higher than the last point. Now for this option called transition, I can use a number of points for that. So I'll pick a point and I'll click the transition option and then I'll click a few more points. Clicking transition each time. When I'm finished, I can choose how I want to draw through those points. So I'll pick grade and this time I'll say minus two. So I want to slope downward at a grade of minus two. And Civil 3D will set the elevation for all of the transition points that I just selected. Notice also that I can do an arc, I launch the arc option this time and zoom in just a little bit. You can see that it automatically creates the arc tangent to the segment before it. And just like with the other selections, I can specify an elevation grade difference or any of those. I'll use the default grade which is just Civil 3D remembering what I did last time. And I'll do minus 2% again. Next I'll do a line segment. And if I want the segment to be tangent to the curve before it, I'll use the length option. And I'll type in a length of 100. Finally, I'll need to choose the elevation for that point that I just created. And again, we'll do a grade of minus two. When I'm all finished drawing the polyline, I can simply press enter or press escape. And the polylines been completed in my drawing. Here you see it in 2D view or plain view, and here, we see in a 3D view. So that's from scratch or using the simply create feature line option. What about some of these other choices? We'll get to create from objects last. Next, I want to do from alignment. So I'll click the command, select an alignment in my drawing. And the big choice I have to make here is which profile do I want to use? Here I've got an existing ground profile and a finished round profile, something to do with storm. I want to match the finished ground center line elevations of the road so I'll select that option. I've got options for weeding and how to handle curves and I've got the ability to choose what style I want the feature line to be and some choices to handle tessellation on spirals. I'll go ahead and accept the defaults for that and click OK. And you'll notice the new feature line was just created down the center line and I do have some additional weeding factors that I can apply. I'll click OK. And the feature line has been drawn. We can see it here in green, in 3D view. And it's a direct match of the profile and the alignment that's in my drawing. Next, we can create them by corridor. So I'll click create feature line from corridor. I'll come out here and select this daylight line. Notice by the tool tip, there are actually two feature lines here, one called daylight and one called daylight fill. And depending on where I am in the corridor, I may have quite a few of them all stacked up on top of each other. Here I have half a dozen or so. I'll click this outer one and press enter. I can click others if I like. And you can see that it's kind of recognized the names of those two items in the corridor and given them the same names here. Now, since I don't want both of them, in this case, I'll uncheck daylight fill and just use the daylight option. Notice also, I can choose a site, style, layer and so on. I'll click extract. And the new feature line was created in purple in plain view. And also in purple in 3D view over here. And you can see that it's an exact match to the edge of the corridor. Now I can use that feature line to maybe build a swale or some other greeting feature off of the edge of the road. Which brings me to this last option which is create feature line from step offset. This is just like the AutoCAD offset command, except that you're going to provide two pieces of information, the horizontal offset and the vertical offset. So I'm going to say that my horizontal offset is 10, 10 feet. I'll select my feature line that I want to offset. I'll pick the one that we just created. I'll pick a side, and then I'll choose how I want to do the elevation of the resulting feature line. I can do it by grade by a constant elevation across the whole feature line, a difference in elevation or even variable. Let's do this by grade and let's use a 3% grade. And finally, for the feature line command that I've been saving for last is create feature lines from objects. With this command, I can choose lines, arcs, polylines or 3D polylines and convert them to feature lines. I can even reach into x-refs and grab objects from X-refs in the drawing. I'm going to pick this outer perimeter of our parking lot here and press enter. Again, I need to choose a site. If I want, I can name a feature line. I can choose a style that I want it to be, a layer that I wanted to be placed on. I can erase the objects that are being converted to feature lines. Notice I have that option turned on. I can also assign elevations. I'll click OK. And I'm going to assign my elevation as a constant elevation of 2164. Notice that I can do it from a surface. And when I do it from a surface, I can even add some additional points to that surface. I'll go ahead and click OK. And we can see here in 3D view, the feature line that's been created. It's the same geometry as the outside of the parking lot, except that it's been elevated to elevation 2164. So there you have it. That's how you create feature lines in Civil 3D.

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