AutoCAD: Managing Image References

As images are included more frequently in design and technical drafting, the task of managing external image references and maintaining link integrity when transmitting drawings can become increasingly frustrating and tedious. Many have found themselves sending drawings to others only to get return emails about broken links and missing references, leaving one to either fix them, or rely on the experience of the receiving party to readjust link locations. Knowledge of few principles however, can make the process manging image references significantly easier:

1. Organize your directory structures and use relative paths. Most of us have certain directory structures we maintain to organize our drawings and keep everything arranged. However you structure your directories is not of major importance -- keeping the referenced images associated with the drawing file after its transfer is. Consider adopting a directory structure that keeps everything arranged effectively, one solution: Season Year\Employer\Show Name\ -or- Employer\Season Year\Show Name\ Whether you keep your image references in this directory or in another directory under it (my personal preference) is a matter of personal taste. What this allows you to do is more easily use relative paths when referencing images in your drawings. Relative vs. Absolute paths: Absolute paths reference a file using the complete directory structure used to find the file on your computer. Once a file is moved to another computer, the directory structure will very likely change. Consider the example of saving files on the desktop of your computer. The absolute path to a file on your desktop on a windows machince will look something like this: C:\Documents and Settings\username\Desktop\filename.file In this example, username will be replaced with the username associated with the account you're currently logged into on a windows machine. Unless the person you're sending a file to has the same username as you (a rather unlikely scenario), the absolute path to the file you send will be different on the other persons computer. Relative paths, on the other hand, reference a file using the current directory as the starting point. In the case of AutoCAD references the starting point is the location of the file that contains the reference. A relative directory doesn't contain a starting drive letter (e.g. C:, D:, etc) or a leading backslash (\), lets looks at another example: The filename containing the reference is: C:\Documents and Settings\wreality\My Document's\mydrawing.dwg If I were to reference an image in this file using an absolute path it would look like: C:\Documents and Settings\wreality\My Document's\images\image.jpg When I send this DWG and image file to someone else, unless their username is the same as mine, AutoCAD would fail to load the reference because it would be looking for the image using the absolute directory I told it to look in. However, if I use relative a relative path: images\image.jpg AutoCAD will look for the file in a directory called 'images' under the directory in which the .dwg file is saved. As long as the person receiving this file saves it in such a directory, AutoCAD will find the referenced file. Saving relative paths when inserting drawings is a simple as selecting 'Relative Path' from the 'Path Type' drop down menu in the 'IMAGEATTACH' dialog:
   
   Selecting relative paths instructs AutoCAD to reference the attached file based on the saved location of the host file.
2. Using Reference Manager to correct links. Often times you're presented with a file in which the links have been incorrectly identified and AutoCAD is unable to find the referenced item, or you want to check to see that your file will be correctly interpreted once you send it on to someone else. The AutoCAD reference manger allows you to do just that. This often overlooked application resides in the same Start Menu folder that AutoCAD is contained in (by default Start Menu->Programs->AutoDesk->AutoCAD->Reference Manager). Starting Reference Manager and opening a dwg file (File->Add Drawing) presents us with the following:
   
   This dialog lists all externally referenced objects in the .dwg files as well as the current state of the referenced file (Resolved, Not Found). By right clicking on any reference in the list we can select 'Edit Selected Paths...' and modify the path stored in the .dwg file used to reference the object. Following the rules above for creating relative paths will reference the file from the current directory.