Making elliptical arches
Video: Making elliptical archesThis movie we're going to wrap up our quick tour of different arch shapes by doing an elliptical arch. There's not a whole lot of difference between using an elliptical curve versus a circular curve. A lot of the same techniques apply. But I'm going to use the opportunity to not only talk about the elliptical arch, but also make the, profile that we're using along the sweep just a little bit more parametric, or make it a little bit cleaner. So I'm starting in a file here that I've called Arch Seed and it's in the Seed Families folder of the Exercise files.
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Have you ever tried to control the shape of a curved form in the Family Editor? If so, you know that flexing them sometimes throws you a curve ball. In this course, Paul F. Aubin explores several techniques to tame your unruly parametric curves. This includes examples of circles, arcs, arches, splines, and even complex curves like cyma moldings. The real power comes in with formulas, profile families, and proportions, which allow you to mathematically control your curves. At the end of this course, we can't guarantee you'll never have misbehaving curves, but we'll give you several useful tools to help tame them.
- Creating seed families
- Creating circles, ellipses, and arcs
- Controlling rotation
- Working with segmental and elliptical arches
- Using profile families
- Working with cyma curves
- Using fixed proportion and scaling
Making elliptical arches
This movie we're going to wrap up our quick tour of different arch shapes by doing an elliptical arch. There's not a whole lot of difference between using an elliptical curve versus a circular curve. A lot of the same techniques apply. But I'm going to use the opportunity to not only talk about the elliptical arch, but also make the, profile that we're using along the sweep just a little bit more parametric, or make it a little bit cleaner. So I'm starting in a file here that I've called Arch Seed and it's in the Seed Families folder of the Exercise files.
And all I've done is, some of the steps that we've done in the previous movies ahead of time. So, the center reference plane here has been renamed to spring line, this ones' been renamed to top, and I've applied the height parameter right there. Before I actually start creating the sweep, I want to think about where the sweep profile is going to go. And it's going to be when we draw the art shape in here, it's going to end up with a center point right along this reference plane. So I'm going to go to Create, go to Reference plane and add another Reference plane right about here, and I'll just set the distance of that to point 25.
Now you can make that a perimeter, by just adding the dimension between here and here. Pull it over there. And I'm going to take that dimension, and just label it with a new perimeter. I'm going to call that Y1. Now the name of that's not that important, okay? You could call it profile height if you want to, or brick size, or whatever that represents to you. But for now Y1 will do the trick. I'm going to go to a front elevation view. Front back and left right, the orientation in a face based family can be a little bit confusing.
Even though this is front elevation, it would be like we were looking up at the underside of the arch right now, because of the way that we're building it in this family. So really front is, front relative to the screen from a plan view, but it's really kind of almost like bottom in this case. Anyway, you could do this next step from any one of these elevations. It really doesn't matter. I just chose front. But I want to establish how thick I want my arch material to be. So I just need a reference plane here. And I'm going to set that dimension to point two units.
And add a dimension for that, from the reference level to the new reference plane. And I'm going to label that with my existing D parameter, D for depth. Now of course, it's going to flex that pretty considerably there, because D is currently set to two units. So if I really want that to be 0.2, I'll just click right on that dimension, click there, and flex it to 0.2, and that should pull it back again to where it was. So, I now have a reference plane that's going to set the depth of the sweep, and then back here in the floor plan, rough level floor plan.
I have another called Y1 which is going to establish, what essentially is going to be the height of the sweep material. And you'll see what I mean here as we progress. So let's do the path next, we're going to go to Create. And we're going to create a sweep. Now, we'll do sketch path as we've done before. This time, we're going to use an elliptical arc. Or a partial ellipse, as it's called right here. So when you click that, it will prompt you to create this portion of an ellipse. Now, in our case, it's pretty easy, because we want.
Essentially half an ellipse, so you start right here at the intersection of the left and in the spring line and you pull across over here, to the right in the spring line. And it initially will go down but you can just move your mouse to make it go up, and I'm going to snap it right there. Now, because of the proportions that we currently have set, one to two, what I've really created is a circle. Remember that mathematically if you take an ellipse, and you set both axes to the same length, you essentially end up with a circle.
So, a circle is really just a special case of an ellipse. Anyway, let's go ahead and lock everything down. So, I'm going to my alignment here, pick my left reference plane, my inpoint, lock it. My spring line, endpoint, lock it, repeat it on the other side. There's no shortcut to this. You have to do this every time. Okay. Now, that's great, that gets the endpoints locked, but remember with our ellipse, we need to also lock down our two axes. Now how do we do that? Well, you can't really add the dimension trick like I did with the segmented arch movie, because notice it doesn't highlight, the sketch line.
It just kind of refuses to do that. So I'm going to cancel out of there. It turns out that the way you do this is a little different. You select the Arc, and then that will show you two temporary sketch dimensions here and here. And when it's deselected they go away. So the trick is you just select it. And use the little icon to make that a permanent dimension, and make that a permanent dimension. And then once you do that, now I could select each of these and label them with parameters. So, for that one, I'm going to call that minor axis and then this one.
Add a parameter, and can call that major axis. Now if I have any mathematicians watching, technically that would be semi major access, semi minor access, but I'll let you name them anyway you like. Once I'm done, I'll click Finish there, and go to my 3D view, open that up, kind of spin around here, and as we've done before. I can just simply click Edit profile, and sketch in my rectangle. Now the trouble is, in 3D, I don't really see those reference planes that I built to help me do that.
So, what I'm going to do is find a good view that looks at this profile, and that would either be the left or the right view. Because, again, the right way to think about this orientation is, if you look at your view cube here. Like I said before, front is kind of this way, it's almost like underneath. And top is looking down on it. But, here's right view right there. So, if I open up the right elevation, now the nice thing about that is, I can see that Reference plane and that Reference plane that I drew previously. So, I'm going to cancel out of here. And I'm just going to use my Align Cmd, and align and lock this shape all the way around.
So, I'm going to use this Reference plane right here, and align to that. Lock it. This one right here, align to that, lock it. This one right here, and finally this one. Make sure you're getting the reference to here, and lock it. Don't align to the surface, if it says extrusion, that's not what you want. You want to align to the ref level, or there's a Reference plane under there. Those are better choices. I'm going to click Finish, finish again. Take a look, if we go to 3D at what we got.
At the moment, we essentially have a Roman arch. If we flex this, and change the major and minor axis to not be equal, so let's do the major axis at 1.25, and click Apply, you'll see it kind of stretch out in just that direction, and. Unlike the Segmental arch, where this was a round curve, because this is an ellipse, it just has a slightly different shape to it. So, you can see it's following that elliptical shapes instead of that round shape. So it's a very similar approach, slightly different.
Eh, the key is to constrain the ellipse, you have to click on the shape, and to those two make this dimension permanent icons to turn those into dimensions. And then from there the rest of it kind of works the same, and then the only other thing that we added here was the ability to flex the size of the profile. Which you certainly want to be able to do, when you're building these arches to make them fully parametric.
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