Join Paul F. Aubin for an in-depth discussion in this video Fine detail small volute, part of HBIM: Historic Building Re-creation.
In the previous movie we began laying out the small volute for our Corinthian capital, but more importantly we talked about a concept that we'll be seeing again and again throughout the remaining movies, and that is building a spline path that our geometry will be generated from. In this movie, I want to talk about the second half of that process, and that is hosted points on the spline path and the profiles that will sit on those points to help us create the 3D forms. So the file I have on-screen here has the completed version of the path in it from the previous movie, and as you may recall it is a 2D spline drawn on that plane there to make the shape of the volute.
So now what I need to do is host profiles along this path that I can turn into a lofted 3D form. Now, to host profiles on a path, you need to create reference points. So, that'll be our first step here. So I'll go to my Point command, and I want to make sure that the Draw on Face option is chosen, and then I want to click directly on the spline. And I'll place one here, I'll place one maybe about here. Actually I'll place it right at the midpoint because that'll set it at 0.5.
I'll place another one right about here. And then the final one towards the end. Now, you could snap right to the end, but I like to back it off a little bit and then select the point and modify it. So, if you come over to the properties and you scroll down the normalized curve parameter right here you can modify that number to anything you want. So I'm going to set this one to one, and the one at the other end I'm going to set to zero. So that means I'll have a reference point at the start and another one at the end.
Now this one is already at 0.5, because we snapped to the midpoint. If it's not, you can change it to 0.5. And then this one I'll make about 0.84. Now there's nothing really special about the positions of any of these points. I just did some trial and error and I like the results that they give. So, if you want to vary those later, you can. What's important here is if we go to the 3D view, and we zoom in and we look at this, is that now we have this spline path, and hosted on that spline path we have several points, each of which defines a plane.
Those planes can, in turn, host geometry and that geometry will always be perpendicular to the path. And that's what we need to create a lofted form. So now, the way that we create the geometry on the path we're going to look at a few different ways to do that over the course of the next several movies. In this movie, we're going to look at the massing environment equivalent of using a profile. So if you think back to the traditional Family Editor, when you create a sweep, you can draw your sweep path and then you can load a 2D profile family in and use that profile family to shape your sweep.
2D profile families cannot be used in the massing environment. So what we do instead is we use a generic model family. And I've got one open right here, so I've named it PRF_FB, so profile, face-based. And it is a face-based 3D model family. However, as you can see from the 3D view here, I don't have any 3D geometry in it. I've just placed a model line, and the model line is just a simple circle.
So, with that closed shape, when I load that into my other family, it will function the same way as a profile would. So the massing environment won't let you use a 2D family, but it will use a 3D family that has model lines drawn within it. So it achieves the same end result. Now, what I've done in this family is, you know of course I've got my width, and I've got my depth, and you can see that I've got this circle that's kind of centered that way. But I've got a slight variation in here that I want to point out to you.
Notice here that I've got a parameter called Total Offset. So the Total Offset parameter actually allows me to shift the position of this circle off-center, and not only that, but I've built it in such a way that I can shift it either positive or negative. Normally you can't put a negative number in a dimension. If you do, it will fail. So what we do instead is, I've created this reference plane down here, and that reference plane I've set at a fixed distance away. In this case, I just chose the number two.
I chose two because I figured that we would never need to go more than two away from center. If you need to go more than two away from center just move this reference plane and increase this dimension. But this is now your anchor point, and then by doing the math, depending on whether it's a positive or a negative number in the offset field, the profile will either move closer or further away from this reference line. So let me show you that by going to Family Types, and here's Profile 1, here's Profile 2.
Notice that when I apply it it's still the same size, but it does shift a little bit further away. Here's Profile 3. When I apply that, it shifts even further away and it got a little smaller. And then finally, here's Profile 4, and when I apply that the furthest away and it gets the smallest. Now, notice that Profile 4 is using a positive offset multiplier, where Profiles 2 and 1 are using a negative Profile Offset multiplier. And so those numbers are multiplied by the part length and then that gets added to that negative offset value that's fixed at two, and that's what allows it to shift either up or down.
So I built it that way so that this profile can move around, and that's really the key that I wanted to outline here. By letting this profile move around, I will gain way more flexibility when I build my lofted shape from it back in the other family. Otherwise, I would have to go to a 3D spline. So by building this offset this way, I don't need a 3D spline. I instead am shifting the profile closer and further away from the 2D spline and I'm getting the same effect.
So let's go ahead and load this into the project, and it'll try and place itself here in the front view. That's not really what I want, so let me just cancel out of there and go to the 3D ortho view, and now let's see how we can place this into the project. I want to place one of these profiles on each of the four points. So, if I expand Families, expand Generic Models, and then finally expand my PRF_FB, I'm going to start with Profile 1, drag-and-drop it in.
Now it'll initially tell me that it can't place because there's no face, it's trying to place itself on a 3D geometry, I want to click the Set button here to set the work plane. And specifically where I want to set the work plane is on that point that's sitting down at zero. Once I do that, I can change the placement method to Place on Workplane, and now I can snap directly to that point. Now make sure you're getting snapping to the point. If you want to be sure, type SX.
That's the keyboard shortcut for Snap to Point. I'm still in the command. I'll come over here and change to Profile 2, click the Set Workplane again. The second point is the one here at 50%. I'll click it, Place on Workplane, and place that shape right there. Repeat for Profile 3, set the workplane on the 84% one, place on workplane, place it right there. And then, finally, Profile 4. Set, place that on the final one, and place it right there.
And again, make sure you're snapping to the point. So, as you orbit this around, notice that like if we spin it down to top here, notice that the profile starts off centered and slowly is moving it's way out as it spirals around. So now, all that remains to do is select the path, hold the Control key, and select each of those generic models. You should have five items selected over here, and I'll click Create Form. And just like that, it will create this 3D form, and because of that offset, you can see the way it wraps around and actually changes in the Z direction as well as in the X and the Y.
And without that offset parameter, you really couldn't do that with a 2D spline. So that's really the key variable there that makes this work. You could use a 3D spline, but as I say, it tends to be a little heavier. So you see this seam here? I don't really like seeing that. Now there's a neat little trick you can do to get rid of that seam. All you have to do is get this 3D form to participate in either a join or cut geometry operation with some other 3D form. Now I don't really want to join or cut this object with anything, so what I'm going to do is tip the model down so I can see the underside.
I'll come in here and draw a circle, and I want to draw it right on this workplane, so I'm going to set and pick that same reference point down there at the bottom. Then I can draw my circle, and I'll just draw it a random size there. I'll select that circle, and come over here to the drop-down on the Create Form button, and choose Void Form. And when I do that, it will suggest making a little cylinder there, and I want to choose either this or this, well I want it to engage the 3D form.
And do you see how it went up in there and it cut out a little hole underneath? But more importantly, that eliminates the seam. The final thing you want to do is, I don't want to see these ribs either. So I'll make a window around the entire model, or at least around all of the four circles. Make sure you don't get the overall 3D form. Go to Filter, check None, and I want to check just the four Generic Models.
It should say four here. If it says any other quantity, you need to deselect whatever that is, because you want only four. With those four generic models selected, I'll uncheck the Visible checkbox right there. Now here in the Family Editor they'll still be visible, but when you load this into other projects or families, they won't show up. And that completes the small volute. But more importantly, that gives you the complete process of how we're going to create so many of the forms that make up the Corinthian capital.
So in the previous movie we talked about creating that 2D spline path, and how to go about doing that. And then in this movie, we added the points along that path and then added profiles. Now, there's other ways we can add the profiles, so we'll see variations on this theme in later movies, but the essential process is the same. When you select all of the profiles plus the path and Create Form, you get a very organic 3D shape.
- 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