Join Paul F. Aubin for an in-depth discussion in this video Understanding linking vs. importing, part of Migrating from AutoCAD to Revit.
There are two ways you can bring CAD files into Revit, you can import the files, or you can link them. When you import a CAD file, it becomes embedded in the Revit file, and it maintains no link back to the original. So, if the original file should change, and you needed those changes in Revit, you'd be forced to delete the CAD file and re-import it. On the other hand, if you choose Link, it behaves much more like an X-ref in AutoCAD. So, it will maintain a link back to the original, and when the original changes, you can simply go to Manage Links, select the link, and reload it.
So, let's take a look at both procedures. I'm here in an empty Revit project created from the default Architectural Template, and I'm going to go to the Insert tab. And on the Link panel here, we have a Link CAD button, and on the Import panel, we have Import CAD. So, we'll look at both, but let's start with Link CAD. So, in the Chapter_3 file of the Excise Files, I'm going to select the AutoCAD Floorplan. Now, be sure you don't double-click it because if you do, you'll lose the chance to input some of the settings down at the bottom. Now, I want to just point out a couple of these settings to you right now.
Down here at the bottom, we can tell Revit how to interpret the colors that are coming in from the CAD file. Most of the time AutoCAD files are on a black background, and Revit's on a white background. So, if you want to keep the file in color, you could use Preserve, which will preserve the original colors in the CAD file, but often they're not going to look so good on a white background, so it's usually a better idea to choose Invert. That will reverse the colors and make them look a little bit more legible in Revit. Now, you also have the option for black and white, and that's useful if you want to print the CAD file directly in Revit.
Now, you can also tell Revit how to deal with the Levels or the Layers. Levels are part of a DGN file and Layers of course part of a DWG file. Now, I usually just choose All here because I can easily go in later and turn off layers that I don't want to see, but there actually is a Specify option, or you can choose just the visible layers that are coming in from the CAD file. So you can certainly choose one of those other options. For Units, Revit almost always does a good job of interpreting units. So, I usually don't change this. But if the file comes in, and it's way too big or way too small, then what you can do is undo it, come back here, and you can choose an appropriate unit.
So usually, you don't have to do that, my recommendation is start with Auto-Detect and only change the unit if you have to. Finally, the last setting I want to point out here is correct lines that are slightly off axis. This is a handy little setting that they introduced in recent releases here in Revit that helps correct an error that would often appear when you imported a CAD file. You'd get this warning about lines that were off axis, and you have to OK out of the warning. So, this basically prevents that warning from occurring. So I'm going to go ahead and click Open here. And when I do, you're going to see the file come in, and I'm going to zoom in.
You can see that if I move my mouse near the file, the entire thing highlights with a box around it. And if I click on it and select it, it selects the whole thing. So, that entire file becomes a single object here in Revit. Now, when I select it, there are a few buttons that appear on the Modify tab. I mentioned that we can come back after the fact, and we can manipulate the layers if we wanted to. So, the way that you do that is to use this Query button right here, and you can move your mouse around in the CAD file, and it will actually highlight the individual parts and pieces in that file.
So, for example, if I click on this blue line right here, I can see that, that layer is I-WALL. And if I click on this line right here, I can see that, that layer is A-DOOR. Now, it turns out you can even hide those layers in the CAD file if you wanted to. So, I can use this Hide in view button right here, and that hides the door layer. Now, if I later change my mind and realize I hid the door layer but I'd like to bring it back again, I use Visibility Graphics to do that. That's the standard Revit Visibility Graphics command.
Now, I can go to the View tab and choose Visibility Graphics, or I can use the keyboard shortcut V+G to get there. When you get to Visibility Graphics, you're going to use the Import Categories tab to access CAD files. And you'll see each of the CAD files that are in the file is listed here, and you could see there is A-CAD Floorplan, and I can expand it. And you'll notice that A-DOOR is checked off. So, I'll just turn it back on again, click OK, and my door layer comes back. We brought this in as a link, and I want to see what happens if the owner of the file in CAD makes a change. Let's switch over to AutoCAD. And here in AutoCAD, I'm in the original file.
And what I'm going to do is just make a really simple change. And perhaps this closet right here needs to be a little bit larger, so I'll just use a simple stretch operation, and I'll make that closet larger like so, zoom back out, and let's save the file. Switch back over to Revit, and let's zoom in on that same area here, and of course, we're still seeing the original closet. I've been informed that the CAD file has changed. I'm going to use the same Manage Links dialog that I used to manage Revit links in an earlier movie.
Now, when I click on that, the Revit tab is empty. We don't have any Revit links in this file. But you'll notice there is a CAD Formats tab. When I click there, you could see my A-CAD Floorplan is listed here. Down at the bottom, I have several buttons. We can reload it from a different, reload it from the same file, unload it, remove it, I'm going to reload it, click OK, and you'll see the closet gets bigger. Let me zoom back out. That was the basic process to link a CAD file. Let's talk about importing a CAD file now.
I'm going to import a detail file, which is pretty typical one to use import for. Now, to bring in a detail file, I don't want to bring it in, in this Floorplan view, so I'm going to go to the View tab here, create a Drafting view, and I'll call it Details, and I get a blank sheet of paper. And now I'm going to go back to Insert, and choose Import CAD. I'm just going to select this file here called AutoCAD Detail, and for the moment, I'm not going to change anything down here, I'll just accept all the defaults and click Open. Then I'll do a Zoom to Fit which is Z+F.
And it finds the file, zooms in on it, and you can see that it highlights the same way as the Floorplan did. I've got the same Query button, and I could click on things, and I could see what layers they're on, and I can do Hide in view, all the same features are basically available. The only thing I can't do with the import file is if I go to the Insert tab, and I click on Manage Links, if you go to CAD Formats, you notice it's not listed here. The import file is not linked, therefore if somebody were to make a change to this detail back in AutoCAD, I would have to erase it here and re-import it in order to get that change.
So you can see that we have both Import and Link, both are valuable ways to bring in CAD files and incorporate them into our Revit workflow.
- Comparing AutoCAD and Revit
- Customizing Revit settings
- Exploring the Revit interface
- Organizing with categories versus layers
- Understanding families and groups versus blocks
- Using links instead of Xrefs
- Tracing, nesting, and exploding CAD files