After a DGN underlay is attached to the drawing, you can still modify the position, scale, or rotation at any time.
While you can specify the insertion point, scale factor, and rotation angle at the time you attach a DGN file, you may find the need to alter those settings as your drawing progresses. By default, the insertion point of a DGN file is 0,0,0 and its rotation angle is 0. The scale depends on the working units used in the DGN file, the conversion units used when attaching the DGN underlay, and the insertion scale units set in the DWG file.
Once it is attached, you can also change a DGN underlay’s fade, contrast, and monochrome settings from the Properties palette.
Because an attached DGN underlay acts like an attached raster image, general modify commands behave the same allowing you to move, scale, rotate, mirror, array, and so on. You can also affect alterations by choosing commands from the shortcut menu after you select a DGN underlay or from the Properties palette of the selected DGN underlay.
Object Snapping to DGN underlays
If you need to reference locations on a DGN underlay, you can turn on object snapping for objects in all DGN underlays.
Object snapping for DGN underlays is turned on and off with the DGOSNAP system variable or from the DGN Object Snap option on the shortcut menu when a DGN underlay is selected.
While DGN underlay behavior generally follows the behavior of raster images, one exception is the way that grips work. In this case, the behavior more closely follows that for blocks.
DGN underlays normally display only a base grip. The base grip can be used for repositioning the underlay in the drawing. If you have specified a clipping boundary, additional grips appear for each corner of the boundary when the DGNFRAME system variable is turned on. See “Adjust DGN Underlay Appearance and Clipping Boundaries”.
The grip for the base point looks like the base point for a block reference. The base point cannot be reset from within the current drawing file. It is defined in the DGN file.
