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Revit is a robust design and documentation software package that requires no other software in order to function. However, the building industry utilizes many software packages and tools. Fortunately, Revit can read and write to many of the most popular file formats. The most common file format of all in the building industry is Revit's own DWG format. This is the native file format for AutoCAD. If you share files with architects or engineers, there's a good chance that someone on the project team is sharing data in the DWG format. Fortunately, using DWG files with Revit is easy.
So let's take a look. In this chapter, we're going to look at a few different examples, but I'm going to start here in this movie with the LinkCAD function. The LinkCAD function allows me to bring the DWG file into my Revit project but maintains a link back to the original file. This will be really handy if something has changed in the original DWG file, we'll be able to automatically reload the latest changes from that DWG file without having to repeat the whole linking process over again.
So this is largely considered the best practice way to bring in CAD data from AutoCAD. I'm in a file here called Link CAD and it's just based on the default architectural template, and I'm going to go to the Insert tab and click here on the Link CAD button. And that will take me to a browse window, and you can see here that in the Chapter05 folder, I've got a few different DWG files provided, and I'm going to select this one right here, AutoCAD Floorplan.dwg and you can see that that's really just a copy of our two bedroom condo unit that we were using in the last chapter.
Now down at the bottom we have lots of settings and we want to kind of run through each of these. I'm going to start here in the middle with the ones that are a little bit more self-explanatory. How do you want to deal with the colors or the layers or the import units? For colors, we have three choices; we can invert, preserve, or force everything to black and white. The main issue here is that most AutoCAD users work on a black background with bright primary colors. You can see the bright colors over here in the background. Those colors don't look so well on a white background that we have here in Revit. So typically, Preserve isn't going to give you the nicest results.
So you'll want to choose either Invert or Black and White. Now we'll look at an example of Black and White a little bit later, so for now I'm going to choose Invert. This is going to leave the file in color but it's just going to reverse all the colors and make them a little bit easier to see on a white background. CAD files are organized into layers, layers are just how all the data is organized and separated from one another. If you're familiar with the CAD file, you can choose one of the options here like the Visible layers or the Specify in order to choose the actual layers that you want to bring in.
If you're not familiar with the file, it's best to just choose All, see what you get on screen, and then you can manipulate the layer settings after you bring it in. So both are possibilities. Units can be Auto-Detect, that's the default. That's usually the best choice, but if for some reason the file comes in and it didn't interpret the units correctly, you can undo and then reopen this list and choose the specific unit that you need. But normally, Auto-Detect will give you exactly what you want, so I recommend you start with that. Correct lines that are slightly off axis; this is a new feature in 2013.
This is a really welcome new feature, because previously, what would happen is when you bring in a CAD file, you would often get this error message that said that lines were slightly off axis, and it could cause errors. The way that AutoCAD calculates geometry and the way Revit calculates geometry is a little different from one another, and there is a variety of technical reasons why this error would generate. But nonetheless, the error was relatively benign, but it was troubling just the same to see an error appear. So this option corrects the error before it occurs, and it's a welcome addition to 2013. So I highly recommend that you check that box.
For Positioning, you have a variety of choices. We're going to look at a few different options throughout the course of this in the next several movies. So for this first example, I'm going to use the Origin to Origin option which is going to try to take the 0, 0 point or the origin in the CAD file, and line it up with the origin here in Revit. Now the origin here in Revit is typically right about there in the center of the screen. So that's what I'm looking for is to get this file to line up in that general location. If Origin to Origin doesn't work and there's times when it won't work and we'll discuss that a little bit later, not to worry, we can always move the file afterwards.
So it's not a setting that you have to get too concerned about. Choose what you think is the best option, see what results you get, and then make modifications as necessary. I'm going to place it at Level 1, that seems perfectly logical. And then over here, this setting is actually fairly important, when we bring in the CAD file, there's two ways that Revit can interpret it. If we choose Current view only, it treats the CAD file like any other view specific element in Revit. So if you think about tags and dimensions and text, those are view specific elements in Revit.
Choosing current view only would make this CAD file behave the same way. In other words, it would only show in my Level 1 floor plan. If I go to Level 2 or if I go to 3D, it would disappear. That's probably a pretty good idea if you're bringing in a CAD file for every level of the building. Let's say your designer did sketches in AutoCAD, and laid out the rough floor plans for levels 2, 3, 4, 5, and then you're bringing them in to Revit in order to trace over them and create a Revit file. You're probably not going to want to have to manually hide all the floor plans and all the other views.
So using Current view only is a great way to manage that. Now we'll see an example in the next movie where we're going to uncheck Current view only and that's going to give us 3D data from the CAD file, and so obviously, that's a slightly different approach. But in this case, we're going to use the Current view only, and that's going to tell this floor plan to only appear in Level 1. So I'm going to go ahead, and click Open here. You're going to see the file come in. If I click on it, it highlights the entire thing and it selects as a single unit, and it's got this little pushpin icon on it.
That pushpin is there because we chose the Origin to Origin option. Had we chose any of the other options, it would not be pinned and what the pin does is it prevents me from accidentally moving it. So you see how I can't move the object? Now if you need to move it, you can just simply unpin it, and then it's free to move, but I'm going to undo that, so that it's re-pinned. So you always have the option to unpin it and move it if necessary. Now if I go to Level 2, you can see that it doesn't display here. That was the Current view only setting.
Let me go back to Level 1. I'm going to zoom in a little bit. The colors are darker colors. That's because we chose the Invert option, so you can see here what the result of that option was. Now finally, if my assumption here was that this file came from AutoCAD because the designer was working in AutoCAD or perhaps the file was created years ago before we had Revit, and I now want to do something with it in Revit, one of the most common things you might want to do is to actually convert it to Revit geometry.
Now unfortunately, there's no Convert command, we can't just push a button and have it convert, but we can trace over the CAD file using Revit objects and we can actually do this fairly quickly. Let me show you how that works. If I go to the Architecture tab, click on the Wall tool, and I'm just going to use a generic wall for this example. So I'll start with a Generic 12 inch wall. Notice that as I move my mouse around in the CAD file, it's actually seeing the two parallel lines. So those lines are not walls in AutoCAD, AutoCAD doesn't have walls, those are just two parallel lines but it's finding the center line between those lines and I'm going to be able to draw a wall here, like so, and start tracing over the underlying CAD file.
Now I'm going to do a Zoom window over here, get in a little bit closer, change to a Generic 5 inch wall, do some of the interior walls, you see it works the same way. Now notice that I'm being a little loose about this. I'm not actually trying to draw the whole wall, I'll show you why in a second. I'm going to press Escape one time just to reset, press Escape one time to reset, again Escape one time.
And here is why I kind of left some of those off. So you see here I've got these gaps here and here? All I really need to do to, I'm going to cancel out of the Wall command, zoom out slightly. I'm going to take this wall for example and use the grip and snap it all the way up to here. Once I have that, I'm going to go to my Modify tool and I'm going to use this Trim/Extend to Single Element or this one, Trim/Extend Multiple Elements. Now in this case, I want to use this as a boundary and extend both of these walls, so I'm going to use the Multiple Elements option.
In both of these commands, you select a boundary edge and then you select the wall or walls that you want to trim or extend. If I click an empty space, I can reset the boundary, click a new one, and do it again, click in the empty space, reset, pick a new edge, and do it again. So the reason I'm doing it that way is it's actually a little quicker to draw the walls roughly at the center lines because that's what I'm mainly trying to get from the CAD file, and then I can clean it up very quickly with Revit objects.
Now I'm not going to do the whole floor plan, but if we did continue, what you would see is eventually the color starts to disappear, and what we're left with is the CAD file underneath. Now notice that I drew right over doorways and such, that's because when I come back, and I add a doorway, it will automatically cut the holes in the CAD file for me, and then later if I switch to another view such as a 3D view, and so on, remember we did Current view only, so the CAD file is not displayed and I'm left with only Revit geometry.
So regardless of the reason that you might be bringing in CAD files into your Revit project, this is a pretty common scenario where you might have an old CAD file, you need to trace over it. What you can see is, it's a very smooth and quick process that you can walk through, bring the file in, make your changes. If the designer later makes changes to the CAD file, then all we have to do is go to the Insert tab, click here on the Manage Links button, click the CAD Formats tab, and I can select the linked CAD file here in this list, and reload it, and I'll get the latest changes to that file and I can make adjustments to my underlying layout.
So it's a pretty smooth and easy process and very easy for us to marry together legacy CAD data with our current Revit projects.
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