AutoCAD® 2009 & AutoCAD LT® 2009 All-in-One Desk Reference for Dummies®

Chapter 3. External References

The first two chapters of this minibook explain how to create and work with blocks. Blocks form the cornerstone of reusable content in drawings. In this chapter, you read about external references and how you can use them to improve communication and keep file size down. External references are used to link DWG, DWF, DWFx, DGN, and raster image files into a drawing. By linking these files into the drawing, you have the most up-to-date geometry or image displayed. Some types of external references allow you to snap directly to the geometry that they reference.

Note

AutoCAD LT 2009 now allows you to not only view raster images that are attached to a drawing file but also to attach raster images to a drawing file.

Blocks versus External References

Blocks are groups of objects that are assigned a user-defined name. The definition of a block is stored in a drawing file, and when a change is required, the block needs to be redefined. This can be a problem if the block is contained in a number of different drawings. External references maintain a link to a file outside a drawing that contains drawing objects or a raster image; the contents of the file are not actually part of the drawing file that they are being referenced into.

An external reference in a drawing file contains the location of the external file on disk, the file name of the referenced file, and its insertion point, scale, and angle of rotation. When you open a drawing that contains references to ...