Play Nicely with Others (Circles and Lines AutoCAD Tutorial)

1 May, 2007 By: Lynn Allen

AutoCAD 2008 imports and exports MicroStation files.

For as long as I've worked with Autodesk products (more than 20 years now), they haven't played nicely with others. Autodesk practically refused to admit there were any other players out there and consequently didn't feel the need to commingle design data. Of course, today the DWG file format has become the drawing standard by which most of us make our money and the fierce competitors seem to be dropping off like flies.

AutoCAD 2008 is the first release of AutoCAD that plays nicely with others -- and by "others," I'm referring to those who use MicroStation. And, why not support those who for whatever reason have chosen to take a CAD path that doesn't include the magnificent DWG? Can't we all just get along?

I realize that many of you have already figured out how to get around the top-secret society of all things AutoCAD and have found a means for DGN/DWG conversion. But, putting these tools right into AutoCAD increases the likelihood that the files will translate properly because Autodesk has an entire team of great programmers dedicated to DGN translation, so you can get more accurate results.

This month, we will look at the tools in AutoCAD 2008 that are certain to brighten the spirits of those who need and want to work with DGN files.

Exporting to DGN
After you've completed your AutoCAD drawing, you can translate it into the DGN format. Go to File/Export or type in DGNEXPORT at the Command prompt. Here you'll find the new V8 DGN format option.

The new V8 DGN Export option makes it easy to translate your drawings to MicroStation.

After selecting V8 DGN and Save, you're prompted to answer a few more questions to ensure you get the best results possible.

The Export DGN Settings dialog box helps you get the best results possible.

To begin, AutoCAD needs to know what you want to do with any external references in your drawing. If you select Translate all DWG references to DGN files, AutoCAD translates all the referenced files (even nested xrefs) into DGN files and saves them to the same directory as the DGN file with all of the relationships maintained. These new files maintain their original drawing name but with a DGN extension. If a DGN files already exists with the same name, AutoCAD doesn't overwrite it (a key thing to note).

If you choose to Bind the DWG references into one DGN file, all the references are bound first and then a DGN is created from the resulting file. The xrefs are converted to cells inside of the new DGN file.

The last option is self-explanatory with all the xrefs left behind.

External DGN References
You can import DGN references as underlays, much like DWF files. If you have any DGN underlays in the drawing file you are exporting, you must indicate whether or not those files should be included in the export process. The end result would be that these DGN underlays would become DGN references.

Seed Files
AutoCAD uses template files, and MicroStation uses seed files. These files contain the default settings and attributes such as working units. Selecting the correct seed file and conversion units can make or break the translation process and should not be overlooked. AutoCAD 2008 comes with four seed files: two imperial and two metric. You must indicate whether you're exporting a 2D or 3D file, as well.

Selecting a seed file is crucial to proper translation.

You might be better off using your own seed file to get the best results or modify the ones that come with AutoCAD. Below is a chart with more details about the information contained within the seed files.

Details of information you find in seed files, similar to template files in AutoCAD.

You aren't done yet! You also must choose between master and sub units. Selecting master indicates that one drawing unit in AutoCAD translates to one master unit in MicroStation (such as feet or meters). Sub units indicates that one drawing unit in AutoCAD translate to one sub unit (such as inches or millimeters).

After you've selected all the appropriate settings, crossed your fingers and shaken a few chicken bones over your head, press OK and your shiny new DGN file is created!

So, what about going the other direction -- bringing a DGN file into AutoCAD? You'll have no problems with the new Import DGN option, also found in the File menu (or use the DGNIMPORT command). The experience is similar to exporting.

Importing a DGN File
After selecting the DGN file to import, you need to answer a few questions for the best results.

Customize the DGN settings to get the best results.

First off, you must select the DGN design model you want imported into model space. DGN files might have multiple design models, so you may have to make a best choice because AutoCAD only has one model space per drawing. DGN files also have sheet models that translate over to paper space layouts (AutoCAD has plenty of those, so no decision needed here). Only those sheet models that reference the primary design model are imported. They are converted to paper space layouts and include viewports that display each reference to the primary design model.

DGN files can have external references as well. Do you want them to be included in the conversion (all external DGN references are converted to DWG)?

Here's the clincher, though. AutoCAD refuses to overwrite an existing DWG file using this command, which could lead to some unexpected results down the road. You probably won't run into this on the first go-around, but if you were to perform this operation again on the same drawing you'd find that any DWG xrefs would not convert because they would need to overwrite the existing ones. So, here's the deal! Delete those DWG files first or move the whole process to a different directory -- otherwise you'll feel like you're in the Twilight Zone when the files don't update!

You can also choose to import the externally referenced DGN files as the new DGN underlay. This lets you snap to, measure, reference, etc. but not edit the actual DGN file.

Explode Text Node to Text Elements
Text nodes elements in MicroStation are similar to our MTEXT objects -- they are multiple lines of text stored as one element.

When selected, multiple lines of text are divided into individual text objects. This is key if you have any text from the DGN file that was created along a curved path (which we can't do natively in AutoCAD). Otherwise, you might find that keeping the text as a single multiline text object might serve you just fine. A little trial and error here should eventually help you get the results you're after.

And, of course, last but not least, you must select the proper units.

Of course, you might need to make some adjustments along the way to get the best translation possible, but the key here is this is a giant step in the right direction. Anything that makes it easier for all of us to get our jobs done, regardless of the software used, is a beautiful thing, and I, for one, am delighted to see these new features added into AutoCAD 2008! So, a great big "Hoorah!" for Autodesk, and I hope to see more and more of these types of features in the future.

Until next month, Happy AutoCADing!

AutoCAD Tips!

Lynn Allen

In her easy-to-follow, friendly style, long-time Cadalyst contributing editor and Autodesk Technical Evangelist Lynn Allen guides you through a new feature or time-saving trick in every episode of her popular AutoCAD video tips. Subscribe to the free Cadalyst Video Picks newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!

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