Create Topography from a DWG Link in Revit Architecture 2011
Creating topography from a DWG link
When you receive information from a civil engineer, it will always be in either DGN or DWG format. There is no Revit civil package, so these folks are always going to be working in either AutoCAD or MicroStation. Revit does, however, have some simple topography tools, which are going to allow us to build a terrain model based on that CAD data that we bring in. So let's look at the process. Once again, I am in a blank, empty file just created from the default template for the purposes of this exercise. I have provided a civil engineering file that actually is shipped with, and installed with, the default AutoCAD installation.
So this file actually comes from Autodesk and is in the sample files with AutoCAD, and I am just using it here as an example to show you how we can bring that file in and make topography from it. So I am going to go to the Insert tab, click on the LinkCAD, and I've got this AutoCAD Siteplan file right here that I've copied over from the AutoCAD application. It was in the sample file, shipped with AutoCAD. The most important setting that we want to do differently here from the Import Floorplan movie is we want to make sure that we do not choose Current View only when we are bringing in Siteplan data.
This is critical because when we uncheck this box, we are basically telling Revit to treat this imported CAD data as three-dimensional geometry. If we don't use it as three- dimensional geometry, then the topography cannot be generated from it. So, we want to make sure that that box is unchecked. The rest of the settings are less important, but we'll just run through them any way. I am going to go ahead and invert the colors. I am going to bring in all the layers, auto-detect the units. Now, here probably a pretty good idea to go ahead and try the Origin to Origin option and see what happens.
But 9 times out of 10 what's going to happen is Siteplan data, civil engineers are notorious for they've drawn the contours here that you can see, and the origin is 300 miles away at some state benchmark marker. So, Revit doesn't have an easy time reconciling such large distances, especially when they are miles away. They have expanded this in 2011 to a 20-mile radius. It used to be limited at 2 miles, which was more limiting, so 20 miles is better, but still, sometimes it runs into problems.
So there is a pretty good chance we are going to see some sort of an error about this. Let me go ahead and click OK, and the error looks something like that. So, it's telling me that the object was a large distance from the origin, and so they chose Center to Center for me anyway, even though I asked for Origin to Origin. This is not the end of the world because Revit has a feature called Shared Coordinates, which we are going to look at in a future movie. Share Coordinates allows us to reconcile the differences between two different coordinate systems. So at first, you might be concerned about that and say, well, that was not very good of it to arbitrarily move my file.
But it's pretty easy for us to reconcile it back and get it coordinated. So for now we are not going to concern ourselves too much with that warning. One last thing I want to say about the warning is when you get a warning down here in the bottom corner, that's what Revit likes to refer to as a warning that you can ignore, or believe it or not, if you looked it up in the Help file, it's actually called an Ignorable Warning, okay. This means that I can to simply click anywhere onscreen, and the warning will go away, and it doesn't require immediate attention, okay. So some warnings will not be ignorable.
You'll have to click some sort of button in the dialog box, and usually it's a distasteful button like Cancel or Delete Stuff, and we'll see those maybe later. Anyhow, I'm looking at this file, and the next thing that I want to do is I want to kind of assess the file. I want to figure out what I've got here. So, I am going to go to an Elevation view first and just kind of show you that the engineer who built this file actually created a series of contour lines set at their explicit three-dimensional heights.
So each of those contour lines is set at a certain Z height, and that's going to be critical to our success in creating a topo surface from this. If everything is flat, we are not going to get a topo surface. We're just going to get a flat plane. So we need this sort of three -dimensional characteristic. The next thing we need is we need to know which layers in the CAD file are actually contours, so that Revit doesn't try to create contours from these plot lines, or from these roads, or other things in here which would just distort the surface and cause a lot of problems.
We are only interested in the actual lines that are really contour lines. So if I kind of look in this area right here, that's probably a pretty good place for me to do this query. So I am going to zoom in right here, and what I want to know is what layer this bluish color line is, and what layer this darker purple line is? I can do that by simply selecting the CAD file, the whole thing will highlight, and then over here on the Ribbon, I have a Query button. When I click on that, it allows me to select the lines inside the CAD file, and it will tell me the names of those layers.
So this one is called CF-DEP_INDX, and this other one over here is called CF-DEP_INT, which I assume is intermediate. So we are going to take those two layers, and we are going to generate topography from just those two layers. So we are going to go to Massing & Site for that. Click on the Toposurface button, and we have a few options here. Place Point is the default option. In order to use Place Point, you would literally have to specify the Elevation and literally click point-by-point-by- point, every single point you wanted to create the surface from.
Very tedious process if you were doing a site of this magnitude. Not recommended. Instead, we are going to use the button next to it, where it's going to allow us to create from the Imported CAD file. I am going to select the Import Instance and when I do, it will give me a list of all the layers in that CAD file. I am going to click Check None, and then I am going to select those two layers that I just previously queried. So that was why it was important for me to do that query, so I know which layers to choose, and then I am going to click OK. What you are going to see is Revit will go through and analyze all of those CAD layers and generate points at the correct three- dimensional locations for all of those contours.
So I think you'll agree that that's going to happen much more quickly than you and I could go in and place those points manually. So if we zoom out, you can see there is a whole lot of points there. So all I need to do is click Finish, and let's go ahead and click the 3D tool and a little tough to see. So I am going to do two things. I am going to take the CAD file, select it. I can tell it's the CAD file because it highlights with this big box around it, and if I wait long enough, I'll get a tooltip that tells me that's an AutoCAD file. I am going to select it, and I am going to hide that object, okay.
I want to just turn it off and make it invisible. In this case, I am going to do that temporarily, and I can do that down here on the View Control bar, with this little Sunglass icon and just choose Hide Element. That's going to make that CAD file just go away, just temporarily. We are just kind of hiding it. And then the next thing I want to do is click this little white cube over here, which is different shading modes. The default is Hidden Line. We can do Shaded, Shaded with Edges. Shaded with Edges usually gives a little more contrast, so I am going to go ahead and choose that, hold down my Shift key, spin my mouse, and you can see that there is a surface here, and it's a little subtle, but it's actually picking up the 3D contours that were in the CAD file.
So very easy to take a CAD file and convert it into a 3D surface, and then we can start actually placing our building on the site.
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