Join Paul F. Aubin for an in-depth discussion in this video Fine detail shaft, part of Project Soane: Recover a Lost Monument with BIM.
- Let's continue with the fine detailed version of our column and move on to the shaft. Now I'm back in the diagram here, the scanned illustration and I'm looking at the shaft and specifically it's the fluting that I want to talk about here, around the shaft. The Vesta at Tivoli Temple uses very unique fluting. And you can see that the channels are actually squared off at both the top and the bottom. Not only are they squared off at the top, but down at the bottom you can see they have this really interesting sort of sloping chamfer down here at the bottom of the channel.
Now, in a more typical fluted column what you'd actually see is a rounded top and bottom that's more like it was scooped out like with an ice cream scoop, or you know, with a router bit or something like that. So, it turns out that actually creating it with that rounded top and bottom, is actually way more difficult than this channel here with the squared off top and bottom. So, when I was writing Renaissance Revit my first instinct, the first thing I tried to do was to use voids to create the channels. I figured you just do a void, you'd array it around, and you'd be in business.
But Revit wasn't having any part of it. So I had to come up with alternate techniques to do the fluted columns in Renaissance Revit, well I'm not going to actually use either of those techniques here. I'm going back to my original idea of using voids, but because of the Vesta column, and because it's got the squared off top and bottom, it actually works just fine. So that's the process that we're going to walk through. We're also going to create this molding here at the top. So let's switch over to Revit, and I have a start file open on screen and the pieces that are already in here is the sweep for the shaft of course, and we've already talked about this sweep.
This is exactly the same sweep that we talked about in the medium detail version of the shaft with the elliptical entasis, the internal profile, all of that so you can go out and review that movie if you want to see that in more detail. Meanwhile, if I zoom in down here at the bottom, you can see that sloping chamfer cut there, at the bottom of the channel. So, if I select this, that's the overall sweep. But if I press tab, and reach in, you can see that I've added a second sweep and it'll be a little bit easier to see that if we go to front view, and zoom in.
So this second sweep is just really a little wedge shape that's been spun around that same circle. If I do edit sweep, there's the shape of the profile. So, to build that is exactly the same as the steps we followed in the previous movie when we did the Torus shapes at the base of the Capitol. So I'm not going to review that here. You can go back to that movie if you want, and you can delete this and get additional practice if you choose to. What I am going to do is stay here in the front view, and zoom in instead here at the top and I'm going to look at an alternative way to create the molding at the top.
Now we could of course go in and create another sweep, we could sketch the shape directly in the sweep, or we could create a separate profile. We could load that profile in and use it on the sweep. But sometimes it's just easier to use a revolve. So that's what I'm going to do right here. Now, to help us get started, I've added some reference planes in both directions, so that we have some stuff to snap to and to avoid having unnecessary parameters, I just use equal dimensions wherever possible to locate those reference planes.
So I'm going to zoom in on this area here and the main curve in this molding is actually an ellipse. So, I'm going to go to Create. Click the Revolve command and I'll choose the elliptical arc. Now I'm going to start the first point right here at this intersection. So it's like one, two, three up from the bottom there. And drag it across until the center snaps at this final one, right there. So you can see that's seven units away and it snaps right to that center one.
And then I'll pull this straight up until it snaps to that intersection there. And I'll click modify to cancel. Grab the grip at the end and snap it back to that point so that it's just a quarter of an ellipse. Then I'm going to go to my toolbox here and choose a tangent arc next. Now I've added this little stray reference plane right here so I'm going to click the end point of the elliptical arc and then come over and snap to this intersection which should give me a 90° arc there, but keep it nice and tangent to the ellipse.
Then I'll switch to a straight line, pull this across to here, pull it straight down here, come across all the way to the center line, back up to the top here, across right there, and then down to here. So all of the rest of that is just simple straight lines. Now as I said if you wanted to do this with a sweep you could, you just wouldn't be able to go all the way to the center because the sweep would fail if you did that, you'd have to leave the center hollow. But otherwise, it would work largely the same.
Let me draw an axis line and that's the point that this profile will spin around. When I click finish, it will create the revolve and if I go to 3D, let's just do an extense and zoom out here, you can see that form that's been created. I'll select it, scroll down, and assign that to the shaft material property to get it assigned to the same material. So that's our topmost molding. Now I'm going to select this void and you might have to use your tab key to reach in there and grab it and that void was created with a swept blend.
So I'm going to delete that void and recreate it now. So, I'm going to delete that and then, I've actually created a section view in this file, specifically for the purpose of creating the swept blend. I just find it a little easier to do it in a section. And what we need to do is create the path of the swept blend and then, what's unique about a swept blend is, it can have two profiles. So, if you think back to the illustration, the shapes of the channels are a half round in here and then straight lines that flare out.
They're very similar in fact, to the Torus shape that we did in the previous movie. So if we scroll down here on the project browser, beneath Families and Profiles, I've created two profile families that are already loaded here in the project and they're just called Flute B for bottom and Flute T for top. And if I edit one of these and show you, you can see that it does have an arc but then the lines come off tangent to the arc instead of making a hard corner. Otherwise, it's pretty much the same form as the ones that we did in the previous movie and I'll let you experiment with that or create you own if you choose.
So we're going to use those two profiles that are already here. So our challenge is going to be drawing the path. Now you may think it's not that big of a challenge, but what turns out to be a limitation with the swept blend is that you can only have a one segment path. So, when I choose swept blend, I'm going to click Sketch Path, it's going to ask me for a work plane. So I'm going to sketch on the center front-back work plane, that's parallel to my section. Click okay. If you use any of these shapes, you could only do one shape.
Well, the problem is, remember the bottom third of the column is straight and then it curves in that really subtle elliptical curve. So that would be two segments. So that wouldn't work here. So what we're going to do instead is we're going to use a spline. Now a spline is not going to be a perfect match to the shape that's there, but we can get it close enough that when we're carving out the void it will be acceptable. So, I'm going to use my spline, zoom in here at the bottom, and the first point that I want to snap to is the intersection right there.
Remember the channel drops down a little bit lower than that chamfer point. So that's this point right here. And I'll click that. Then I'm going to zoom out a little bit, and find that first third. And I want to pull it straight up and click again at that point. Now this is a spline, which means that it can bend in all sorts of directions. So pull up a little bit further and click a second point, because we're going to need that point later to fine tune things, and then zoom out. So we want two points there, kind of close together. And then finally the last point, is going to be up here towards the top.
I've got another reference plane intersection right there. And I want to snap exactly to it. I click my modified tool to cancel out and if you zoom out and kind of look here, you can see that we didn't quite match the curve. But that's where that second point comes into play. So I'm going to go back down to here, select the spline, and now I can use this point and just sort of start pulling it up a little bit. Now, I'm pulling it up and slightly away from the profile.
And if you zoom in, you can see I'm real close. Maybe I want to pull it out just a little bit more. So, I'll just zoom in here, pull it up and out just a touch more, see how I did. So it's a little bit of fine tuning, to kind of get it where you want it to go. But, you should be able to get it really close. So that it matches that curvature almost exactly. Now, once you've got the path, you're virtually done. All you have to do now is click Finish, and then let's go to 3D so we can actually see what's going on as we do it.
And, since I'm zoomed in here at the top, I can go ahead and start with that profile. So that's going to be profile two. So I do select profile two, and then, from the list here, I will choose Flute top. And you'll see that it places that shape right in the correct location. Let me zoom out, scroll down to the bottom, click select profile one, change that to the bottom flute, it puts that shape right in there, and then I'll click Finish to create the swept blend.
Now, when I deselect, it's a solid object. That's because when I was on the create tab, I clicked the swept blend tool. Now there is a separate void swept blend tool and I could've used that instead, but it turns out that if you select a solid, or a void you can come over here to Properties and change it later between the two. So, I'll choose void in this case and that turns that into a void. But then I need to go to Cut geometry, select my shaft, and then select my void to carve that channel out of the shape there.
So, now all I need to do is copy that channel around and we need 20 of them total. So I'm going to do that in plan view, It'll be the easiest way to see what's going on. So I'm going to highlight near the channel, press the tab key until I can select the swept blend. Once I've got it selected, I'll go to my array tool. Now, the array tool defaults to linear array, we want to change that to radial. It also defaults to group and associate, which is often very useful, but in this case I don't want to group and associate.
I know that I need 20, and that's never going to change. So I'm going to put in 20. I'm going to move to the second element, and I want to use this button over here to place the center of rotation right in the center of the column. And then finally, I'll click in the Angle field, and if you take 360° and divide that by 20, you get 18. So I'll put in 18, press enter, and now I get all of my channels arrayed around. Now, sometimes it skips one, I'm not sure why, so I can just do Cut geometry, select the overall form, select the missing void and that will take care of it.
And when I go back to 3D, we now have our completed fluted column. So, using a swept blend as a void it becomes real easy to cut these channels out of the shaft. But I want to warn you, that if you need the rounded tops, it's a lot trickier. And I did not have anywhere near as good a success with that. So if you want to learn alternative ways to create fluted shafts you can check out some of the exercises in chapter 12 of Renaissance Revit.
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