AutoCAD Map 3D toolset uses polygons by default for import and export. If you do not want to use polygons, for example, for compatibility with an older drawing, you can select the option to import polygons as polylines. You can also change the default setting for this option.
To change the default setting for importing polygons
You are asked whether you want to use polygons.
If you turn off mpolygons, AutoCAD Map 3D toolset creates closed polylines for polygon objects that it imports.
To change the default fill for polygons
All polygons you create or convert will use the new default fill. You can change the fill for an existing polygon with MAPMPEDIT (Edit Polygon command).
To change the display of polygon edges