Join Paul F. Aubin for an in-depth discussion in this video Linking AutoCAD DWG files, part of Revit Architecture 2016 Essential Training (Imperial).
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- Revit supports the import and export of many popular CAD formats. Chief among them is the DWG format used by AutoCAD, so it's quite likely that some of your projects will have a need for at least one DWG point at some point in the project. So, in this movie, I'd like to talk about the process to link a DWG file. We can also embed the DWG, but it's much more common and usually more preferable to use the linking process, so that's what I'm gonna cover, here. When you link, you maintain a connection back to the original file, so if the original file is changed, you can update that link and get the latest and greatest changes directly here in Revit.
So, I made a file here called Link CAD, and I'm here on my Insert tab, and you can see that there are actually several different kinds of files that we can link, and in this movie, we're gonna look at the Link CAD button, which gives me access to several file formats. DWG, of course, DXF, DGN, SAT files, and even SketchUp files. So, since DWG is, by far, the most popular, I'm gonna choose that. Now, I have here a copy of the floorplan of my condominium unit, drawn in AutoCAD. So, perhaps my designer worked in AutoCAD originally, and now, I want to bring that AutoCAD file into Revit to begin creating the Revit project.
Now, if you look at the bottom of the dialogue, you can see that there are several user-configurable options that we have when we're linking in a CAD file, so let's talk about a few of these. The first is, if you look over here in the preview window, you can see that the CAD file is in these bright, primary colors. Now, that's very common in AutoCAD for people to work in those bright colors, but those colors probably wouldn't look so nice on Revit's white background. So, down here, we have our color options, and we can either preserve those colors, invert them but keep them in color and just kind of reverse the hues, or convert everything to black and white.
In this example, I'm gonna choose the invert option, and I'll talk about why in a few moments. Now, CAD files are usually organized into layers or levels, so here, we can choose which of those layers or levels we want to bring in. All of them, just the visible ones, or we can even open a dialogue and specify the ones we want. In this case, I'm gonna leave it set to all and bring in all the layers. You can always turn off the layers you don't want, later, if it turns out that there's some of them you don't wanna see. Now, under units, it has all the standard measuring systems that are common in architectural production, and Revit usually does a pretty good job of auto-detecting, so that's what I'm gonna leave.
If, for some reason, it comes in as the wrong size, you can always undo and then figure out what unit it's supposed to choose and come choose it off of here. Occasionally, you'll get an error message that displays that the lines are slightly off axis. This is just a precision calculation that Revit's doing, and this check box right here corrects for that, so usually a pretty good idea to leave that checked. Over here, we have an option for current view only. Keep in mind that, when you're bringing in CAD data, it is not Revit data, so Revit doesn't actually know what's in the CAD file. It's gonna just treat it as just graphics.
It's just gonna be linework, so with this setting, you can tell it whether or not the information should display only in the current view, or whether it should be treated more like model elements and display in all views. Now, in this case, I'm gonna choose current view only, and this way, if I went up to another floor plan, like second floor or third floor, I'm not gonna have to worry that the floorplan for the first floor is showing through on all those levels. It also wouldn't show if I went to a 3D view or a section view or anything like that. So, Current View Only is usually a pretty good choice for floor plans, particularly if you're planning to trace over them, which is what we're gonna do in a few moments.
Now, over here, you've got your positioning options, and there's lots of choices available. Now, a pretty common thing to do is to try and match up the origins, so I'm gonna choose the Auto Origin-to-Origin. Now, if I move this dialogue out of the way, typically the origin in a Revit project is right about here, in the center of the screen. So, when we bring in this file, you're gonna see that it's lined up with that point right there, choosing Origin-Origin. So, lemme go ahead and click Open, here, and see what we get. Now, if I move my mouse near the file as it came in, you'll notice that it highlights with a box all the way around it.
If you look at the upper right-hand corner of that box, it's right about at the center point where I indicated the origin of this Revit file was. If you click to select the file, it highlights the entire file, so it's treated as one continuous piece in the Revit project, and there's this little pushpin icon that appears right here that's designed to prevent you from accidentally moving this. So, notice that, if I tried to drag and move this file, I can't actually do that as long as it's pinned. Now, if for some reason, you decided you did need to move it, you can just simply unpin it, and then, you're free to move it, but I'm gonna do Control Z and undo that, select it again, and repin it.
Now, in a previous movie, we talked about selection toggles, and you may recall that they were down at the lower right-hand corner of the screen, or they were up here on this dropdown right here, and in this case, we have both a link and a pinned element, so if you uncheck either of these check boxes, the Select Links or the Select Pinned Elements, you will no longer be able to select this file. Now, you don't need to uncheck both of them. Either one would do the trick, but as long as you uncheck one of those, not only will you be preventing people from accidentally moving the file, but they won't even be able to select it.
Okay, so why do we bring in a CAD file in the first place? Well, once again, maybe my designer was working in AutoCAD, but I really want to make this project in Revit. So, at this point, what I might do is I might take this CAD file and I might start trying to add Revit geometry in place of the CAD geometry. Now, unfortunately, there's no sort of auto-convert. You can't just push a button and convert it to Revit geometry, but what you can do is zoom in, so I'm just gonna roll my wheel, here, so I can get a better look, and you can actually start to trace over this CAD file using Revit geometry.
So, I'm gonna go to my Architecture tab, click my wall tool. I'll change the wall type to a generic 12-inch wall, and a really nice feature about working on top of the CAD file, here, is notice that, if you move your mouse, it kinda sees the center line between those two parallel lines in the CAD file, so all I need to do is wait for that little dashed line to appear and begin clicking the points to create my wall geometry. And what I'm gonna do is just sort of create a little L-shape, right there, and then, I'll escape out. I'm still in the wall command.
I only pressed escape once, and then, I'm gonna come over here and choose a thinner wall, like maybe a generic five-inch wall to draw some of these interior partitions, and I'll zoom in just a little bit closer, and I'm not even going to worry too much about getting these super-precise. Now, you can turn corners and stuff, if you want, but notice that I can just sort of place some of these, kind of in seemingly random locations, but what we're gonna do next is we're gonna use our trim and extend tools to clean this up.
So, we've got those basic walls, and they're centered in the positions relative to the parallel lines in the CAD file. So, let me escape out of there. Now, if I go to my Modify tab, I've got two tools, here, that I can use: the Trim and Extend Single Element, or the Trim and Extend Multiple Elements. Now, I'm gonna choose the multiple elements, in this case. This one allows me to choose a boundary edge and then extend or trim multiple elements to that boundary edge. So, for example, I could use this exterior wall over here as the boundary edge, and then, notice when I hover over this wall right here, I get a little dash line indicating that it's gonna extend over and connect itself to that wall.
The boundary is still active, so if I click on a second wall, it will continue to extend over to the same location. Now, at this point, I've got all the walls I wanted to extend over to that wall, and I wanna choose a new boundary. So, the way you do that is to just simply click an empty, white space, and that resets the command but stays within it, and then you can pick a new boundary. Now, with walls, it doesn't actually matter if you click this side or this side, or even the center. The entire wall will be seen as the boundary edge.
Now, if you want, you could click one at a time like I did a moment ago, but I'm gonna do Control Z, Control Z, and it's actually a little faster to pick your boundary edge and then do a crossing window, like so, and you can select several at once. Now, in this case, I only had two walls, but lemme Control Z again, suppose I had made this selection. You can see that all three of those walls would go across. Now, if I reset again, click this one and then click here, notice that it will actually trim it back, so this command is both a trim and an extend command, and if I drag through these two, the boundary edge was still active and those two will extend out.
So, you can start to see the reason, now, why I chose a color option to import the CAD file. Notice that the Revit wall geometry is in black, and it is covering up the colors as I go along, so as I'm tracing, it kind of gives me an indication of where I've been and what I still need to do. Now, the other strategy you may notice is that I made the walls go directly over the door openings. Well, this is because I'm drawing Revit geometry, now, so unlike CAD files, where you would have to trim and stop and start in between each location, here, when I simply place these Revit doors in the locations where they ought to be, they automatically cut the holes in the walls.
Now, finally, if I go to my little default 3D view icon right here and kind of hold my Shift key down and spin around, notice that I'm getting live Revit geometry, full-blown 3D geometry, but the CAD file does not display in this view, and once again, that's because, when I imported the CAD file, I chose that Current View Only option. So, you can use these CAD files in a variety of ways in Revit, and in this case, I showed an example where we could just very quickly use it as the basis to trace over it and begin creating a Revit model, but in some cases, you might have a discipline working on your team that's not working in Revit, maybe it's a lighting designer or some other kind of collaborator that's working with you, and you could simply link that CAD file in and leave it as a permanent part of the Revit project.
So, it's a very versatile way to work that allows you to very quickly and easily marry together both Revit and CAD geometry within the same project file.
Paul also shows advanced techniques for modeling stairs, complex walls, and partially obscured building elements, as well as adding rooms and solid geometry. Finally, discover how to annotate your drawing so all the components are perfectly understood, and learn how to output sheets to DWF, PDF, or AutoCAD.
- Understanding BIM and the Revit element hierarchy
- Navigating views
- Creating a new project from a template
- Adding walls, doors, and windows
- Adding plumbing fixtures and other components
- Linking AutoCAD DWG files
- Rotating and aligning Revit links
- Working with footprint and extrusion roofs
- Adding openings
- Adding railings and extensions to stairs
- Creating stacked and curtain walls
- Hiding and isolating objects
- Adding rooms
- Creating schedule views and tags
- Adding text and dimensions
- Creating new families
- Using reference planes, parameters, and constraints
- Plotting and creating a PDF