Join Paul F. Aubin for an in-depth discussion in this video Controlling rotation, part of Revit: Family Curves and Formulas.
If you've been following along in the movies, in order in this course, then in the previous movie you saw that we talked about controlling an arc and one of the ways that we could make it flex parametrically in a reliable way. And I alluded to the fact that we would look at other ways. Before we get to some of those other ways, I want to lay some other foundational materials. So, in this chapter, I'm going to be talking about rotation. Now I've covered this topic before, in some other courses here at lynda.com. So if you've reviewed the Revit Family Editor course here at lynda.com, some of this information will appear as review.
But I think these concepts are important foundation to much of the work that we'll be doing throughout this course. So I think some of it bears repeating. So in this movie we're going to focus on how we create parametric rotation. And while that is not exactly the same thing as curvature, it's certainly related. So I'm back in my GM seed file, the seed file that we created at the start of the course. And you can work in your own copy of this, or you can open up the one that I've provided in the exercise files. And as we've seen in previous movies, I'm just going to take this box that we have here on screen and delete it, and we're going to build something else in its place.
When you want to control rotation in a family, you really can't do that with reference planes. Reference planes, technically are infinite, so it becomes very difficult to put any kind of rotation on that reference plane and have it flex in a reliable way. It 'll kind of drift and move on you. In other words, you can't pin down the pivot point of the rotation. So to pin down the pivot point of the rotation, which is absolutely crucial to getting reliable rotation, you need to use something called a reference line.
So I'm going to go to the Create tab. And over here on the datum panel, we're going to choose the Reference Line button. Now, the reference line is sort of a special case object. It behaves like a line, it has two end points. You can lock those endpoints down. But it also has some other special features to it. So let's start by laying out the reference line. So the way I usually do this is I snap the first point to some known intersection in my models. So in this case, I'm going to use the intersection in the center of the family, and then I usually pull this thing out at some known standard angle.
So I'm going to go at 45 degrees. And you'll notice that the dimension along the length is a little bit bolder than the dimension at 45 degrees. Revit refers to these as listening dimensions and you're able to actually type a number into a listening dimension and it will input it directly onscreen. So I'm at about five units right now, so that's what I'm going to type. I'm going to type five, and it's going to go right into the length of that line, and when I press Enter, and then I'll cancel out of the command, I'm going to get a reference line that's exactly five units long.
Now let me go ahead and zoom in on this a little bit, and what I'm going to do is temporarily take this floor plan view and just stretch it out a little bit larger so that we can zoom in closer and get a better look at what we're doing. Now at this end you get the automatic sketch dimensions that you might expect, the zero and the zero. At this end, because I made the length of the reference line exactly five units long, I'm getting these sketch dimensions that are somewhat random. So I'm going to ignore those for right now. Those don't concern me.
But I want to take care of the zero and the zero. I can do that in the same way that I dealt with the points on the curve. In other words, I can align and lock. So, I'm going to come over here and click on the reference plane. And then when I move my mouse towards the end, notice that if I'm right at the end point, it will highlight a little dot there at the end. Now make sure you're not doing this, because if you do, it will actually change the rotation of the reference line. That's not what I wanted, so I'm going to do control z to undo that.
What I want is the reference plane and then that little dot right there, that's only going to align in the x direction in this case, and I'll lock it. And that removes one of the dimensions. And then I'll align in this other direction to that same dot and lock it. And that moves the other one. And so now what I've done is locked this end point permanently to this intersection. So think of that like your hinge now. And, now I'll be able to spin this reference line around and keep it locked at this common center.
Now I want to do two things to the reference line, and that'll help me get rid of these two automatic sketch dimensions. The first is, we made this thing exactly five units long. Well, like we've seen in other movies, if I select it, a temporary dimension will appear with a little icon here, and I can make that a permanent dimension, and as soon as I do, that eliminates one of those dimensions. Now I can select it, label that and I'm going to call that L, that's going to be the length of this line.
If I flex that you're going to see the length of this reference line will change. Now because this temporary dimension was here in the background. You're probably a little surprised by the way that that flexed. Notice that it actually changed the angle of the reference line. However, because we locked this endpoint it stayed at that location right there. So this effectively behaved like a hinge. And in order to maintain this distance and keep that hinge locked the only thing it could do was change the angle as you've seen here.
Okay, so if I change this back to five and apply. Oh look we get another surprise from Revit. You might've expecting, as I was, that it was going to snap back to a 45 degree. But, in fact, what it did, was it reevaluated the situation and gave me a whole new automatic sketch dimension, which is just one more example of why, I personally, don't like to rely on these automatic sketch dimensions. So let's leave that the way it is, click okay. And what I want to do instead is negate this automatic sketch dimension.
I want to get rid of it. And so what I need is, a new kind of dimension. I'm going to create an Angular Dimension. So when I choose that, I can set the reference plane as the start angle. The reference line as the end angle and just pull that dimension out here somewhere. Cancel out of there, select the dimension, and I'm going to label it with a new parameter. You probably already can see that the automatic sketch dimension has disappeared. Adding this angle dimension eliminates the need for the automatic sketch dimension.
And I'm going to give this a name, and I'll just call it a and click okay. And at this point, I can now go to Family Types and I can flex that angle to any number I want. Let's try 25 degrees and Apply and you'll see it change. Let's try 45 degrees. Let's try 65 degrees. And you're getting the general idea. So, now, we've got the two things that we need to control rotation. We have the N point pinned down, effectively behaving like a hinge, and we have an angle which determines how much rotation we want.
And, it's usually a good idea to flex that angle to several different variations to make sure that it's working the way that you expect, but that's the essential foundation that you need, to control rotation parametrically in the Family Editor.
- 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