Create alignments from objects

00:06

In this video, we're going to go ahead and use a new alignment creation method.

00:10

We're going to go ahead and use the Create Alignment from Object.

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So what we need to do first is we need to find the object that we're going to create an alignment based off of.

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It was one of the lines that we turned on when we unfroze one of the C-ROAD layers.

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And if you zoom in to the end of this, what looks like a cul-de-sac,

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we will end up turning into a cul-de-sac, you'll see a polyline here that is blue.

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And what we're going to go ahead and do is we're going to take this polyline, we're going to turn it into an alignment.

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So in order to do that, we're going to go up to the Home tab of the ribbon bar and navigate over to Alignments.

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We're going to dropdown, we're going to select Create Alignment from Objects.

00:48

And then what Civil 3D is going to ask us is to select the first line, arc, and polyline.

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We're only going to deal with one polyline.

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If you have like a line that went into a curve that then went into polyline and they were all touching each other at the ends,

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they're all snapped on to each other's endpoints,

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then you could select each individual part, Civil 3D would turn all of those entities into one alignment.

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What we're going to go ahead and do is just use one single polyline.

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I'm going to select the polyline and then I'm going to hit "Enter" to finish that command.

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And then it says, press Enter to accept alignment direction.

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If you notice inside of here, there's an arrow and it points in the direction that the alignment is going to be built.

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If you don't like that direction, you can hit R for reverse.

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If you don't hit R for reverse and you just hit Enter and you accidentally meant to have it go the other way, we'll talk about that in a second.

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So I'm going to hit "Enter" to accept that direction of the alignment.

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And then I get the alignment creation window.

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I have the option for the name, the general information, the site, the style, the label set.

01:57

And then I have a conversion option, add curves between tangents.

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So if I have a bunch of lines or polylines with no curves in them, I can define what I want the radiuses to be inserted into my alignment would be.

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I have a bunch of curves, so I don't want to add curves between tangents because I have no tangents.

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And then I have the option for erasing my existing entity, like we did when we created a feature line from object.

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I don't need this polyline anymore, so I am going to leave erase existing entities checked.

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And then I'm going to click "OK".

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If you had design criteria that you wanted to place on to this alignment, you could also still define that here.

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I'm going to leave my starting station as 0+00 and I'm going to hit "OK".

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And so what Civil 3D does is it creates that alignment for me with the stationing and the orientation that I specified go in this direction.

02:45

If I had accidentally chosen that and not wanted to go this direction, and instead I wanted to read the opposite direction,

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there is an option for correcting that.

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What you have to do is you have to select the alignment that you want to work with and then go to the Modify section of the contextual ribbon bar,

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for the specific alignment we've selected and dropdown and choose Reverse Direction.

03:11

It's really a good idea to make sure you choose your directions of your alignments before you start using them,

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to create anything else inside of Civil 3D because what you'll notice if I click Reverse Direction, I'm going to get a warning.

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And what it's telling me is that anything that is associated to this alignment, when I reverse that station,

03:31

it's going to possibly be detrimental to some of the objects that are associated with that alignment.

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Because a lot of the objects you're going to link off of your alignment are associated with the stationing of that alignment.

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So in mid-design if you change the stationing by reversing the alignment, you could have some major problems happen with your design.

03:51

So it's a good idea to lock in your stationing as you want it before you start working with the design for the rest of the project.

03:58

So we're going to go ahead and leave these as they are.

04:00

One item to note: when you do create a alignment from an object,

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it's different than when you create it using your tangent to tangent with curves or tangent to tangent with lines, then adding curves in later.

04:14

When you have a tangent to tangent with curves or tangent to tangent no curves and then add curves later,

04:20

you have a lot of grip edits that remain dynamic, and the tangencies are linked.

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So if I have a line here and I've created a free curve between two tangents,

04:31

then this curve knows that it needs to be remaining tangent to those two straight segments.

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And so if I take a grip and I move it, what Civil 3D does is it retains that curve tangency.

04:44

And so it takes these lines and modifies them and retains the tangency to that curve at the specified radius.

04:53

And you have basically these dynamic links between grips.

04:56

So I can take a grip and I can slide it along that tangency and modify my radius, and it moves the tangency, shortens it up, expands the radius.

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Or I can expand the radius and it maintains those tangencies and slides them back along the tangent sections.

05:15

When you create a alignment from an object, it doesn't maintain those dynamic tangency links.

05:24

So with these curves, I drew them in as tangent curve.

05:29

When I created this polyline, I created it by drawing a straight line, creating a circle, and then filleting between them.

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So by doing the fillet, it created a tangent curve between them.

05:41

But because they weren't created using the alignment command, I don't have those retained tangencies.

05:46

And so what I can do is if I grab a grip edit, I could edit these and what happens is they aren't forced to keep the tangency between them anymore.

05:57

So that's just one thing to look out for.

05:59

If you want to be able to grip edit and modify your alignments later,

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then you would want to create it using tangent to tangent with curves or without curves and then add the curves in later.

06:11

Otherwise, you just don't retain those tangencies.