About Importing MicroStation DGN Files

The import process translates basic DGN data into the corresponding DWG file data and specialized data as a best fit. There are several translation options to determine how certain data such as text elements and external references are handled. You can manipulate text elements and external references, and select the conversion units based on DGN unit settings.

Understand the Limitations

The import process handles DGN objects and properties that have a direct correlation to DWG objects and properties without any issues. For example, levels in MicroStation translate directly to AutoCAD layers. However, DGN objects and properties that have no direct correlation to DWG objects and properties may not translate completely. The following are known limitations resulting from this issue.

• Data with built-in features or variations are visually approximated. For example, text and dimensions with specialized formatting, and color definitions might be customized.
• Entities in the DGN file that have a color property set for a symbol lose the symbol color when imported as a block.
• Linetypes associated with multilines do not display.
• Entities with DGN line styles in nonuniformly scaled blocks may look different to how they appear in MicroStation.
• Line style modifier settings of an element in the DGN file are lost when exporting them from AutoCAD back to MicroStation.
• The Closed property of a DGN polygon or closed polyline changes to No during import.

See the DGNIMPORT Conversion Table for specific details about the scope of importing MicroStation objects and other data.

See the DGNIMPORT Unit Mapping Table for specific details about unit conversions when importing MicroStation objects.

Recommendations

To optimize the data transfer from the MicroStation® DGN file format, request that the creator of the MicroStation drawings consider the following recommendations:

• Create a separate DGN file for each design model.
• Do not reference sheet models from design models.
• Minimize the use of custom objects and other data unique to MicroStation.
• Use ByLevel for color, line style, and weight properties.
• Use simple patterns and pattern styles.
• Use TrueType text fonts rather than SHX text fonts.
• Use defined styles for dimensions and text rather than a “none” style.
• Use simple dimension styles if possible.
• Use shared cells as opposed to normal (library) cells.
• Work primarily in one format, DWG or DGN, rather than switching back and forth.

Conversion Units

When importing a DGN file, ensure that the DWG file's drawing units match either the master units or sub units of the DGN file. For example, assume that you are importing a DGN file with master units set to meters, and sub units set to millimeters. You can set the DWG file's drawing units to meters. When importing the DGN file, in the Import DGN Settings dialog box, specify master units as the conversion unit.

Import Custom Line Style Definitions

If a DGN file does not contain linetype definitions, and these definitions do not exist in any *.rsc files in the support path, all linetypes in the DGN file are displayed as a continuous linetype in AutoCAD. To ensure that custom linetypes are displayed, copy the corresponding *.rsc files to the support path. Alternatively you can add the RSC file path to the search path in AutoCAD in the Options dialog box (Files tab, Support File Search Path).

Import Referenced DGN Files

While importing a DGN file, the program displays the Import DGN Settings dialog box. To convert referenced DGN files to block references, select the Import into Current Drawing option and the Translate References to Blocks or Xrefs option. To convert the referenced DGN files to DWG external references, ensure that both these options are cleared.

Microstation Standard Line Styles

Do not use the MicroStation standard line styles 1 to 7. The scaling for these line styles is based on output device coordinates. For best results, use custom line styles.

Manage Translation Mapping Setups

Translation mappings define how DGN properties translate to DWG properties. You can use the DGN Mapping Setups dialog box to create, modify, rename, or delete mapping translations based on your company’s CAD standards. For example:

• Change DGN level names to appropriate DWG layer names
• Remap unsupported DGN linestyles to DWG linetypes
• Remap lineweights and adjust color mapping

The DGN Mapping Setups dialog box displays when you click Mapping Setups in the Import DGN Settings and Export DGN Settings dialog boxes. You can also use the DGNMAPPING command to display this dialog box.