Option has been added to DWG Save options that allows for setting how a sheet model is saved to DWG with the desired level display state.
In past versions of MicroStation levels display in DWG file create from DGN could be control by level display settings in Save As DWG/DXF Options. If set to Global, the AutoCAD layers visibility is controlled from the global setting, and the levels that are turned off on a per-view basis are turned on in the AutoCAD file. If set to one of the eight views, the AutoCAD layers are not visible if they are turned off either globally or in that view. Although MicroStation allows you to turn on and turn off levels either globally or on a per-view basis, AutoCAD allows only global control.
While DWG does not support per view based level display, in addition to globally frozen layers such viewport can have a list of frozen layers. When a source view is selected for DWG save, the view level display may be applied to Viewport Freeze, with following options:
The first two options are essentially holdovers from MicroStation V8i.
1. Viewports & Global Layers = Use Level Display For Viewport Freeze Only turned OFF in previous versions
2. Viewports Only = Use Level Display For Viewport turned ON in previous version
3. Force Global Layer Display =Turns all layers on globally
Option #3 applies source view level display to viewport freeze. Additionally, it also globally thaws all the levels. Following is the impact of the setting on different DWG features
Use option #3 if you want to ensure your sheet model to have correct level display in the DWG layout and care less about level display in the default model. In an instance where global display for a level is turned off in the DGN, the level will be turned on in the DWG file. The significance of that is to give the full control of level display to a layout model. This gives more of a "What You See Is What Get" (WYSIWYG) appearance in the layout model.
i.e. If you had a sheet model with a design model attached with the same level name(s), there was no way of differentiating the levels when saving to DWG format. AutoCAD does not have a separate viewport layer and layout layer although it does support viewport freeze. So if the level is turned on or off in the sheet model the and the reference level had a different setting the DWG file could not show this.
You can now have the same display for the layout and viewport in AutoCAD as it would appear in MicroStation, but the layers would all be globally turned on.