Add curves, lines, and spirals to an alignment

00:05

In this video, we're going to talk about how to add curves, lines, and spirals to an already existing alignment.

00:11

And then we're going to go ahead and actually use what we're talking about,

00:14

and add a couple of curves to our existing alignment inside of this drawing.

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So first, what you need to be able to do is get back into the alignment creation toolbar,

00:24

it's associated with the alignment that's in the drawing already.

00:27

If you were to dropdown and choose Alignment Creation tool, you're going to go ahead and actually create a new alignment.

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So what you have to do inside Civil 3D is you need to go to the alignment that you have created, select it, and then click on Geometry Editor.

00:41

So inside of Geometry Editor, it brings up the alignment creation toolbar that's associated with the specific alignment that's already in the drawing.

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So one thing we didn't talk about in the last video, that's an important piece of the editing abilities of your alignment creation toolbar,

00:58

is that you have a grid view of your alignment.

01:03

So inside of here, if you click on this where it says Alignment Grid View, what you can do is you can see all of the information,

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related to your alignment, what type of item it is, what the parameters are, and what the start and end points are, and that information.

01:19

If it's locked, obviously you can't change it, but you can unlock it.

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But when you unlock it, it doesn't really allow you to change any of the objects inside of here,

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and that's simply because these are all interacting with each other.

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And so if I modify a direction or a length or a start and end station of one object,

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it's going to cascade through the rest of the alignment and modify bunch of other things and you don't want to have that happen.

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So for now, it's all empty when we add our curves in, we'll go back into here,

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and you'll see that there are some items available to be modified inside of this grid view.

01:59

So what we're going to do is we're going to jump down into the options for adding information to our alignments.

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And so the first three options are, you can add a point of intersection, you can delete a point of intersection,

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or you can break a point of intersection.

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These options just basically are going to either dissolve that point of intersection,

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and move the line in between the existing start point and that point of intersection.

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Or it will add a new one and so it will change the tangency between two existing point of intersections.

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Or if you break a point of intersection, it's going to get rid of the links between the point of intersections.

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So if I broke this point of intersection, it would remove the two links between that point and this point.

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We're not going to deal with those. What we're going to deal with is we're going to deal with adding lines, curves, and spirals.

02:49

And so what is important to note inside of adding lines, curves, and spirals is,

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there are three prefixes to the type of curve, line, or spiral that you're going to add, and those are fixed, floating, and free.

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And they're not necessarily the most intuitive names for how you're dealing with things.

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But what you need to realize is that a fixed curve or a line or a spiral, what fixed means is that you are placing that object based on fixed points.

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So you will click all the defining points for that entity.

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A floating entity has one end that is connected to an object inside of Civil 3D and the other end is being connected to a fixed point.

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So, say, we wanted a floating line, it would basically create a line that was tangent to an already existing curve,

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or going from the end of an existing curve, and then you would pick the end point of that line.

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So the line floats along the object until you pick the end point.

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Same thing with the curves. You float along the object until you pick the end point.

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That's kind of why floating is chosen as the name, like a floating curve and floating line.

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When we talk about free curves and free lines,

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what free curves and free lines are is they are actually going between two existing objects inside of Civil 3D.

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So a free curve is between two tangents or another curve and a tangent.

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But you go between existing entities and you either choose a radius or a through point with the lines, you're going between two curves basically.

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So you're going with one curve tangency and then creating tangency to the next curve.

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And then with spirals, it's kind of the same thing, except for what spirals are,

04:49

as you spiral into a curve and then you spiral out of a curve or you spiral into another curve and then spiral out of that curve.

04:55

But spirals are very specific and I don't use them very often.

05:01

They're very design-specific as well.

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So you're most likely going to be seeing lines and curves in your day-to-day design practices.

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So moving on from here, we're going to go ahead and actually add some free curves.

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So we're going to take our dropdown for our curve, we're going to choose free curve between two entities and a radius.

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And so what Civil 3D is going to ask us is it's going to say specify your first entity.

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My first entity is this tangency here, my next entity is this tangency here.

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And we are going to be asked, is the curve solution greater than 180 or less than 180?

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So does the line is basically outside of this or inside of this?

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We're doing an inside curvature, so we're going to go ahead and choose inside or less than 180.

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So I'm going to hit "Enter" and then it's going to ask me, what I want my radius to be?

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I could also choose curve length, tangent length, chord length, mid-ordinate distance, external degree, and then degree of curvature.

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I'm going to go ahead and go with 60-foot radius curve.

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And I'm hitting "Enter" and it now places a curve in here, it's tangent to that section and this section.

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Then I'm going to go ahead and do it again. It says specify first entity.

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I'm going to select this tangency and I'm going to select this tangency.

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So when I select it on the polyline that we have here, not the alignment.

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So that's one thing you need to be aware of is draw order inside of Civil 3D.

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I have to hover over my actual alignment and select the tangency.

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Now I get a choice of curve solution angle, I'm going to again choose less than 180.

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So I'm going to hit "Enter" and then I'm going to again choose 60 as my radius, and so I'm going to hit "Enter".

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And we have now placed two free curves into our alignment.