Join Paul F. Aubin for an in-depth discussion in this video Creating spline paths, part of Project Soane: Recover a Lost Monument with BIM.
- In this movie, I'm going to back up for a second and talk about a really simple concept in the massing family editor, and that is the concept of a path. Now a path is not a new concept, and it's not a concept that's unique to the massing environment. When you work in the traditional family editor, you have sweeps, and sweeps use paths. You have swept blends, and swept blends use paths. So paths function the same in all cases. It's just the path of travel that the shape will move along to create the 3-D form. Now when you work in the massing environment, the only thing that's different is you draw both of the shapes first before you do create forms.
So whether it's just a straight line path here with a single shape or a curved path here with a single shape or even spline paths, you draw the path and then you create the shape that you want to sweep perpendicular to that path. And the easiest way to create the shape perpendicular to a path is to use a reference point. So if we place the reference point on the path, we've seen this before, but it will automatically create a perpendicular reference plane to that path. so if you draw your shape on that plane, Then it makes it really easy to build your sweep.
So if I had this straight line and that shape, I would get a simple tube. If I had this shape and this curved path, I would get this bent tube. If I have a spline and this shape, then I'll get this more free form shape and then I also have this kind of spline here, which will give me something very similar, but the difference is this. If we look at these things from a front view, you can see that at the moment, they're all completely flat.
Well, this spline here I can't manipulate in the other direction. If I orbit back down to this way and I select it, just tab in there, I can manipulate it this way in a 2-D environment, but I can't manipulate it in 3-D. But compare that to this one where these points here that are actually driving the spline, and there's another one here, those points are actually being manipulated in 3-D. And so now this spline bends in 3-D.
So I like to refer to this spline here as the 2-D spline, and this spline over here as the 3-D spline for that reason. Now you can get much more interesting free form shapes with the 3-D spline, but you pay a cost in file size and performance. So I tend to actually favor using the 2-D splines where ever possible, and there's other ways to get the same level of complexity and 3-D interest using the 2-D spline without using a 3-D spline and it can definitely help manage your file size a little.
Now having said that, I don't want you to dismiss 3-D splines as not useful and not use them as a consequence. But if you're building a family like the one we are here with this Corinthian capital that's very detailed, then every piece of it that you can make perform a little bit better definitely helps. So that's the only concern that I am raising there. And I just want you to keep that in the back of your mind when you're factoring it in with all of your other considerations. So that gives you a little bit of a background on using shapes for the paths of sweeps.
Now let's go ahead and actually build our first sweep path. And the process that we're going to follow for this, I'm going to do it on one of the volutes for the Corinthian capital. We're going to use that process again and again for several of the other parts and pieces throughout the capital. So we'll use if for the volutes. We'll use it for the leaves. We'll use it for some of the other free form shapes. So once you understand how to create this path using the 2-D spline, then we're going to just repeat that process again and again. So specifically the one that we're going to build right now is one of the volutes.
So the volutes are the scrolling forms at the corners of the capital, and we've got the larger ones at the corners, and we have the smaller ones on the interior. Now you can see the shape of the smaller one very clearly right here on the interior on that 45 degree elevation. So the spline shape that we want to draw is going to go largely straight, and then it's going to go around this corner here and make this little hook at the end. So that's the form that we're going to be building. And back here in revvit, I have a starting file already open onscreen.
Now the name of this file is fine volute small path. And this is just a copy of the medium detail version of the small volute. And as I say, we're going to use the same process for both volutes and for most of the leaves. So it's the same basic idea. You start with the medium detail version, and then you get rid of the 3-D form. So I'm going to tab in and select the 3-D form, and delete it. But I want to keep all of the reference lines.
Because the reference lines tell me what the overall shape of this form is supposed to look like when it's done. So now I want to draw the path, but I want to do that in a view that's more conducive, so I'm going to work in the left elevation and zoom in and now that scrolling path with the little hook on the end, I just need to draw it inside this P shape right here. So, again, I'm going to keep these for reference, but I'll draw my spline within that. Now again I'm going to use the 2-D spline. Revvit calls it spline and spline through points.
I call the spline, the 2-D spline, and the spline through points, the 3-D spline. That's just how I think of them. Okay, so I'm going to go with the spline and my first point I'm going to place right on the reference plane down here. And in fact, you can snap it right to that end point if you want. Or just really anywhere right down there. Then I'm going to pull it straight up to about here, and I always add an extra point because if you immediately start to curve, it curves a little too dramatically. But if you move up a little bit and add a second point, you can kind of temper the amount of curving that's going to go on there.
And you kind of have to just sort of make an educated guess here on how many points you need this path to have. So as I'm sort of looping it around, I'm kind of thinking about that. Now here where I want it to do the little hook I'm going to kick out to the right and then come back up to the left here, like so, and then cancel. So that's the real rough shape. Now a couple things to point out here. First of all, I drew the shape within that overall frame of reference lines.
But I've left room all the way around because we're going to have a solid geometry there that's going to follow this path. So it's going to have thickness on both sides. So you have to kind of have imagine where that path needs to occur. The next thing is that this is actually a model line. You're usually going to want this to be a reference line. So you can go ahead and draw it with a model line, but then just select it, come over here to the properties pallet, and check this box right here, "is reference line", that will turn it into an reference line.
So even if you forgot to click the reference line button, you can easily take a model line and turn it into a reference line later. And it will change green. That will be a clue that it is a reference line and also when you highlight it, it'll have that dashed line at both ends because there's a work plane at each end of a reference line. So those are the clues that you've got a reference line. And then what you do is you just use these little control handles, and you start fine tuning the shape to make it approximate more closely the shape that you want it to have.
So I'm kind of giving myself a rough margin all the way around there that's about the same, and then I'm going to let it tilt just a little bit here, and possibly move this point down at the bottom. Now the most important thing to understand about a 2-D spline is the two end points are different than all of the other control points. If I just grab this end point and start to drag it, notice what happens to the entire shape. Do you see how not only is it actually rotating the entire shape, but watch really carefully if I just move it straight up.
It's actually scaling the shape proportionally. So that's one of the major benefits of the 2-D spline. Now I'm going to undo that so it goes back again. So that's actually really powerful. What that tells us is if we want to make this parametric, all we need to do is align and lock the two end points and then when we scale those two end points, it will scale the entire shape and maintain the overall shape and proportion that we drew, which saves you a lot of effort in terms of trying to parameterize this entire curve.
Now should you actually want to move just that end point, you need to tab in. And then you can select just that end point and drag it. And if I want to kind of fine tune the shape a little bit before finalizing it, I can do that. Likewise, here, if I want this end point to stop right on this line, I can tab in, grab that, and then snap it right to this line. So that's how you can start to fine tune this thing. And then you either align and lock to reference planes or simply add dimensions to those points and put parameters on those dimensions.
Assuming that you actually want to control those locations parametrically. But that's the basic process for creating a 2-D spline. And then you can place points along that 2-D spline and sweep our forms along there. So you're going to see that in the next several movies we're going to see lots of these paths. We're going to have these paths drawn in as these 2-D splines and then there will be points and shapes along those paths. And that will create the overall forms, whether it's a leaf or the volute or whatever the shape is, this is a fundamental, backbone concept of pretty much the rest of the geometry that we need to build in our Corinthian capitol.
NOTE: Registration for the rendering phase of Project Soane opens in January 2016. Render the Revit or RBX models in your favorite Autodesk software for the chance to win great prizes from HP and NVIDIA.
- Researching source materials and source drawings
- Sketching and modeling architecture
- Setting up the project in Revit
- Modeling overall forms
- Using system families
- Adding details such as columns and moldings
- Creating an interior model
- Rendering the project