Wednesday, May 7, 2008

DWG visibility in Revit projects

When you link or import a DWG file into your project (with the option "Current view only" unchecked), Revit sees this information as part of the building model and will use standard model visibility rules to display it. If you check the above mentioned option, Revit will see it as view-specific "annotation" and that DWG will be visible only in the view where it was imported/linked.

The use of DWG files in Revit projects varies. The most typical applications are to pull from one firm's detail library and for use as background drawings, such as site surveys, casework backgrounds, etc. I know, not a great use, but when transitioning, you need to somehow eat that elephant in small bites, especially when project size is large and Revit knowledge is not substantial!

When used as backgrounds, DWG visibility could get a bit confusing. For example last week I was helping someone with their project. This user linked a DWG on the first level and another on the second level. Typically, if you open the second floor plan, you would not expect the first floor DWG to show up. The team wanted to quickly bail out and turn it off manually on the second floor plan by unchecking the subcategory visibility in the Imported Categories tab, but that's just bad practice in my opinion. If you go this route, you'll have to manage visibility in every second floor plan view! Not very efficient, isn't it? The key is to understand why it was showing up and prescribe a cure.

We checked the View Range and it was set correctly. We opened the linked file in ADT/ACA and looked at it in side elevation and saw a number of lines going up in the Z direction. Once your View Range can see any geometry in the DWG file, the entire link/import shows up. The DWG link/import doesn't act as a cuttable object; instead, once the View Range overlaps a part of the DWG, it acts as a switch and turns the light on over the entire link.

So next time your "2D" DWG seems to misbehave, just check for those maverick elements that turn it into a 3D object and zero out their Z coordinate values or lower them so your View Range doesn't overlap these elements. You'll be pleased with the results ;)


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2 comments:

Unknown said...

had the same problem, tnx for sharing the solution.

Dave Baldacchino said...

After all these years eh? :) Good to know.

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