Revit supports the import and export to 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 the need for at least one DWG at some point. So in this movie, I'd like to look at the process to link in a DWG file. We can also embed a DWG, but in this movie I want to look at the linking process. When you link a DWG. You maintain a connection back to the original file. And sort of that original file changes in a new way you can actually go to a dialog and reload to capture this latest changes. So mean to file called linkCAD and its just created from the default architectural template and there is no geometry in here at the moment. I am going to go to the insert tab and click the LinkCAD button. Now what you will see here is there actually are several different file formats that we can link in.
And as I said we are going to focus on the DWG for the time being but the process would work nearly the same for any of these other file formats. With the exercise files, I have a few different files included, and I'm going to choose this one here, AutoCAD floor plan, and you can see the preview over here on the right. It's just a simple floor plan of basically the condo layout that we were working with in the last chapter. So, let's look at some of the settings here in the middle. Let's start with colors. There's a few different ways we can treat the color information coming in from the imported CAD file. We can force it to black and white or we could either invert or preserve to maintain it in color. Now we'll talk about black and white in a later movie. Invert and preserve, the only real difference is if you look at the preview over in the upper right hand corner.
You can see that the colors are very bright primary colors. That's pretty common in an Auto CAD file, but, they might not look so good on the white background here in Revit. So, if we chose preserve, we would get those bright primary colors. But if we choose invert instead, it'll take all those color values and it will reverse them, so that they look a little bit nicer on the white background. Now CAD files are organized in, either, layers or levels. Autocad DWG files use layers. Microstation uses levels. And you can bring in all of those layers or levels or you could specify to bring in just certain ones.
Now if you're very familiar with the file, you can choose to specify and pick from a list. But in this case, I'm going to choose all and bring everything in. You can always go later and turn on and off the layers that you don't want to see. For units all the standard measurement systems are available and Revit usually does a pretty good job of auto detecting the correct units. So I recommend that you start with auto detect, and if for some reason it doesn't correctly interpret them then you can undo and reimport and choose a specific unit off the list. Now, sometimes Revit will generate error messages when it's bringing in a CAD file because it finds certain lines that are a little bit skewed. Revit calls those "off access lines," and they have this check box here to kind of auto correct that problem for you so that you don't generate the error. So, I recommend you leave this turned on.
Now, under positioning, we have a lot of options. We can use center to center, we can do a manual placement, an automatic placement. For this example, I'm going to choose origin to origin. Now, that will take the origin, or the zero-zero point in the CAD file, and it will line it up with the origin in the Revit file. Now, if I move this box out of the way here, the origin in the Revit file is usually right about here in the middle of the screen. Kind of in the middle of this location between all of these elevation marks. So that's the location it will use. The final setting I want to consider is over not he left, the current View Only check box.
Now it may be checked for you, it may be unchecked. Revit remembers the last setting that you chose. The choice here determines how Revit will interpret the cad data coming in. If you check current view only, which is what I want to do in this case, I want to make sure it is checked. It will treat this CAD data as view specific geometry in other words it will be similar to text, or dimensions, or tags in Rivet and it will only appear in the view the (UNKNOWN). So if you look over here in my Project browser in the background you can see that I am in level 1 floor plan that's a bit bold.
If I open up level two or the 3D view or one of the elevations. This CAD file will not appear in those views as long as current view only is turned on. If I un check it, then it will treat the CAD data as part of a model. And so it would show in all views regardless of the one that it was brought in. In the next movie we will look at example of turning off the Current View Only setting. So for this example I want you to make sure Current View Only is checked. And then we'll go ahead and click Open. Now, as you can see, the colors have reversed from what they looked in the preview.
So the walls in particular are nice bright blue instead that bright yellow color. If I move my mouse around the file, you'll see a box highlight around it. So when you have a linked file Revit just highlights it with a box all the way around, and if you were to click to select it, you'll see the entire object select. So it doesn't matter which object. You can't reach into the individual elements, you pick the entire file. Now, if you look where that corner of that box is, you can see that it's right about there, at the location where I indicated would be the origin of this Revit model. Now, if I select the file, you'll notice that it has a push pin on it. That's another by product of using the origin to origin option and that just simply prevents you from accidentally moving this file. Now, you could always unpin it if for some reason you decided that you needed to move the file.
So it's perfectly fine to unpin it if you no longer want it at the origin. I'm going to undo that with control z. I'm going to re-select it, and I'm going to pin it again. Now as you may recall from the selection toggles movie in chapter two, we can also get to the same options down here on the right hand side of the status bar. So here we actually have an example of two of those situations. This is a linked CAD file, and it's also pinned. So if you recall, the select drop down here, under the modified tool, has some options to prevent links or pinned elements from being selected.
So if I unchecked select pinned elements, for example, I can no longer highlight or select this CAD file. Now we also have a different option for select links. Now, right now they're both turned back on, so I can select again. But if I turn off Select Links now I can no longer select it. Now it's not necessary to uncheck both. One or the other will do the trick. But in either case, what that would do is prevent you from accidentally selecting this CAD file, and moving it with other modifications that you make. So it can be a little bit safer way to work to maintain this file just as essentially a reference.
Now I'm going to zoom in on the CAD file and let's talk about one of the reasons we might want to have this link in the first place. A very common scenario might be that you actually want to start converting what you see here in this file into Revit geometry. Now unfortunately there's no automatic convert. We can't just click a button somewhere and have it convert the geometry. But what we can do is very quickly and easily trace over this CAD file. And if I go to the Architectural tab, click the Wall tool. And I'm going to choose the 12 inch generic wall here. What you're going to see is, there's a really handy feature that we can take advantage of here. Notice that Revit would find the center line between two parallel lines in the CAD file.
That's going to make really easy for me to click and start tracing over that underlying CAD file and doing that very precisely. I am going to add couple of walls there, zoom in a little bit closer change to a smaller size like a 5 inch generic. And you don't even have to do this terribly precisely. I'm just going to draw a wall making sure that it's at the center. That's what I'm concerned about press escape one time, make sure this wall is at the center. Now in some cases you'll be able to turn the corner but in other cases you don't even really have to worry about it too much.
And the reason for that is it's very easy to take these walls we've begun drawing and then use Revit Modify tools to kind of clean it up. So, I'm going to go to these tools here, we've got trim and extend with a single element or with multiple elements. Now, I want to take both of these walls and extend them out to this one out here, now let me cancel out of my wall command. Go to my Modify tab. And I'm going to choose that trim and extend multiple elements. This lets me pick a boundary edge one time. And then select more than one object that I want to extend to that.
Now, I want to stay in this command, but I want to reset my boundary edge. So I just click an empty space to do that, pick a new boundary edge. Extend this one and this one. Click an empty space to reset. Pick a new boundary edge. Extend this one. Empty space to reset. Here and here. Empty space to reset. Here and here, and so I can quickly take these walls and kind of extend them and clean them up with one another. Now you see one of the advantages of bringing the CAD file in in color.
Notice that the underlying color starts to disappear as we begin to trace over it with the Revit elements. And so in a really large floor plan if you were doing this work you would be able to tell what you had completed and what still needed to be done. By simply noticing where the color (UNKNOWN). Now you may also notice that I'm drawing the walls directly over openings, so I'm going to go back to the Architecture tab, pick on the Door tool. Choose a size and these are Revit elements now so they will automatically cut holes in these Revit walls. And if we go to a 3D view, hold the shift key down orbit around you will start to see that what I am left with is Revit geometry that's been created very precisely over the underlying CAD file.
But notice the CAD file does not displayed in this view, that's because when we first brought it in, we checked that box for Current View Only. And so the only view that shows the CAD file is the Level 1 floor plan. All the other views, it's invisible. Later, if the original owner of the CAD file sends me an update I can go to the Insert tab. Click Manage Links, go to CAD formats, select it here and reload it. And I'll get the latest changes to that CAD file. So any time you need to use a cad file in your Revit projects, its a simple matter of just linking it in, placing it where you want to go.
And then you can use that CAD file in a variety of ways such as tracing it over to create Revit geometry as we've see here.
- What is BIM?
- Understanding Revit element hierarchy
- Navigating views
- Creating a new project from a template
- Refining a layout with temporary dimensions
- 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
- Plotting and creating a PDF
Skill Level Beginner
Q: Is this course valid for all of the Revit architecture products? Are there any movies in this course that do not work in Revit LT?
A: This course is designed to work for anybody learning any of the Revit architecture products, including Autodesk Revit (available as part of the "Autodesk Building Design Suite"product), Autodesk Revit Architecture, and Autodesk Revit LT.
However, some individual movies in the course are not valid in Revit LT, due to the limited feature set of that application. Those movies are:
Chapter 3 - Accessing multi-user worksharing projects
Chapter 5 - Establishing shared coordinates
Chapter 6 - Using the shape editing tools to create a flat roof
Chapter 7 - Working with stairs