Levels

MicroStation PowerDraft levels are the same as DWG layers. In MicroStation PowerDraft, levels can be identified with both level numbers and names, but in the DWG file format, layers are identified only with names.

Another difference in DGN and DWG files is the way that the display of levels (layers) is controlled. In MicroStation PowerDraft, each view can have its own display configuration, or levels can be displayed globally throughout the file. In AutoCAD, layers are only displayed globally — they affect all viewports. (A viewport is analogous to a reference attachment.)

Working with Levels That Will Be Saved to DWG Files

When working with a DGN file that will be saved to a DWG file:

Use level names rather than level numbers, since level numbers are not supported in DWG files.
To define how levels are converted to layers, use options on the General and Remap tabs in the Save As DWG/DXF Options dialog.
To control the display of levels, use level filters. Level filters are analogous to DWG layer filters. MicroStation PowerDraft supports layer filters in DWG files from AutoCAD 2000 and later releases. Within MicroStation PowerDraft, you can also create, edit, and save layer filters to DWG files. Layer filters are loaded when a DWG file is opened, and changes are written back when the file is saved.
To control display of elements in the selected levels, use the Level Display dialog. If you want to freeze elements in levels, select Global Freeze. You can also control level display with the Global Display or View Display modes.
Alternatively, you can use the Level Manager dialog to control element display and freeze settings on a level-by-level basis.
When saving to a DWG file, you can choose to omit geometry on frozen levels. To do this, turn off the Frozen Layers option on the Save As DWG/DXF Options, Filter tab.
Any of the element symbology settings (color, line weight, and line style) can be defined as with the value of ByLevel, which is similar to the ByLayer setting in AutoCAD. When an element that uses ByLevel symbology settings is placed on a level, it uses the symbology settings assigned to that level.
To control the symbology settings for each level, use the Level Manager dialog. To be consistent with the DWG file format, always set symbology to ByLevel, since AutoCAD does not have a setting similar to Overrides.

Note: DWG files commonly use the ByLayer setting, since this was the default method for setting the appearance of objects for many years.

Working with Levels in DWG Workmode

In DWG workmode:

Levels can only be identified by names, not numbers, since level numbers are not supported in DWG files.
To control how levels are displayed, use the Level Display dialog. In DWG workmode, you can use the Global Display mode, or opt to freeze elements with the Global Freeze or Viewport Freeze mode.
Alternatively, you can use the Level Manager dialog to globally control element display and freeze settings on a level-by-level basis.
Element symbology (color, line weight, and line style) can be defined ByLevel, which is similar to the ByLayer setting in AutoCAD. When you place an element on a level, it uses the color, line weight, and line style assigned to that level.
To control the symbology settings for each level, use the Level Manager dialog. In DWG workmode, Symbology is always set to ByLevel; overrides are not allowed.