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Thursday, November 19, 2009

Starting Your Revit Model from a 2D AutoCAD Drawing | CADuzer

This is almost a year old, but I just found it stored in my Google Reader starred items. For any of you Rewbies out there (Revit Newbies...I just made that up) this is a great tutorial from Scott on bringing in your CAD drawings for use in Revit.


I received an email recently from a woman named Monica asking if I would go through the process of importing an AutoCAD DWG file into Revit and modeling from it. We very often jump to the very complicated features of software and sometimes ignore the basics, for example, how to get into the program and start working. So, I’m going to go through how to place your drawing into Revit and start working with it. One thing I’d like to suggest, however, is that you look at one of my earlier posts, Shared Coordinates in Revit (and AutoCAD), which is what I’ll be talking about first. OK, here goes:
Let’s take a look at a simple AutoCAD drawing that I want to import (fig. 1):
You can see here that we’ve just got some walls, doors and windows and they’re all on their appropriate layer. Now, let’s bring them into Revit.

  • 1. In Revit, within a new project, click File –> Import/Link – CAD Formats.
    2. When the Import/Link CAD Formats dialog box appears, after locating the drawing, at the bottom of the dialog box, check the box next to the word Link.

  • The next important option comes from the pull-down menu next to Positioning. The tells Revit how, and more importantly where, to insert the DWG. If your drawing was drawn in a random location in AutoCAD, the specific location in Revit is not important so, from the pull-down menu, you should choose Auto – Center to Center. This also assumes that there are no other drawings that you plan on importing that might rely on the positioning of the original drawing. If there are, and your drawing in AutoCAD is close to the origin (0,0), then you should choose Auto – Origin to Origin. Again, only choose this option if your drawing in AutoCAD is close to the origin. If it isn’t close to it (and Autodesk refers to anything beyond 1 mile from the origin as not close) then you should choose Manual – Center and follow the steps in the other post I referred to above, to acquire the coordinate system from the imported DWG.

  • 3. For this example, we’re going to choose Auto – Center to Center since our location is random and no other drawings will be imported which might rely on it’s position in space.

  • 4. In the middle of the bottom of the dialog box you’ll see three more options, the first of which is Colors. Some people like to choose Preserve so they can easily see that, since objects drawn in Revit are black (by default), any objects in color came from AutoCAD. Most of the time, I like to choose Black and White. Choose that.

  • 5. The Layers option allows you to choose which layers from AutoCAD you want to import. Leave this on the default option, All.

  • 6. Finally, Import Units allows you to specify the units of the drawing being imported. This is important because Revit’s architectural units are feet by default while AutoCAD’s architectural units are inches. While you can keep this option on Auto-Detect, I like to set it to inches just to be sure.

  • 7. Finally, the Place at pull-down menu lets you choose on which level you want your drawing placed. We’ll leave this on the default Level 1 as well.

  • acfig02

  • 8. Click OK to import the file.

  • 9. Next, we need to create Revit objects based on the imported CAD data. Let’s start with the walls. The exterior walls are 6″ masonry walls. On the Design Bar, click Walls and then from the Type-selector, choose Basic Wall : Generic – 6″ Masonry.

  • 10. We could certainly trace over the lines from the AutoCAD file, but there is a faster way. To the right of the Type-selector pull-down, click the Pick Lines arrow.

  • 11. Click the pull-down menu next to Height and choose Level 2.

  • 12. Next to Loc Line, click the pull-down menu and choose Finish Face: Interior. This is telling Revit that the Interior walls that you’ll create should remain fixed. In other words, the wall will grow to the exterior (which is the line from AutoCAD you’ll be selecting) if you changed it to a different thickness in the future.

  • acfig03a

  • 13. Place your mouse over one of the exterior wall lines until it highlights AND a dashed blue line appears inside your sketched walls. In many cases, if you now tapped the Tab key, Revit would try to select all connected walls allowing you to create all of the exterior walls in one shot. This feature works better when trying to select more than one connected Revit object as opposed to an imported AutoCAD line. Click the exterior line and the new Revit wall will be created.

  • 14. Repeat this process for all of the exterior walls.

  • 15. We’ll want to repeat the process again for the interior walls with the wall type Basic Wall : Interior – 4″ Partition (1-hr). Since this is not a wall type built into the standard template file, you’ll need to duplicate one of the others and modify it’s structure. Using the method described in Step 13, use the Loc Line: Finish Face Interior just as before and create the interior walls as in figure 4 below.

  • acfig04

  • 16. Finally, we need to insert the windows and doors. Since part of the doors and all of the windows are currently obscured by the newly created walls, click the Model Graphics Style button at the bottom of the Revit window and choose Wireframe.

  • 17. Place doors and the varying sizes of windows using the object snaps available in Revit.

  • 18. Once finished, if you no longer need to have the DWG as an underlay, click File –> Manager Links.

  • 19. When the dialog box appears, select the drawing file from the list, and click Remove.

  • The completed Revit model will look as it does in the image below:
    If you’ve got any questions, please feel free to comment on this post and I’ll answer as soon as possible.

    Starting Your Revit Model from a 2D AutoCAD Drawing | CADuzer


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