About Opening Drawings

You open drawings to work on them just as you do with other applications.

TrustedDWG™ Drawing Files

DWG, DWT, and DWS files created with Autodesk applications and RealDWG™-based applications are trusted by Autodesk. When you open a TrustedDWG file, the following icon displays in the status bar.

If the DWGCHECK system variable is set to On (1), an alert box is displayed if

• The drawing file format is AutoCAD Release 14 or later and
• The drawing file was not originally created by an Autodesk application or RealDWG-based application.

For more information about TrustedDWG, click the TrustedDWG icon.

Change the Default Drawing Folder

Each time you start the product, the last folder that you used for opening or saving a file is set as the default path in the standard file selection dialog box. Alternatively, you can specify a fixed default folder with the program shortcut icon in Windows. For specific instructions, see the topic To Change the Default Drawing Folder.

Resolve Missing References

When you open a drawing, you are notified when an external reference such as an xref, image, or underlay cannot be located. If the external reference was moved to a different folder or drive, use the External References palette to locate the file.

Note: Missing shape files are often the result of custom shapes being used in a linetype. Browse to the missing linetype file, or place the shape file in the folder with the drawing or one of the support paths defined in the Options dialog box. For information about custom shape files in linetypes, see "About Shapes in Custom Linetypes".

Recover Defective Drawing Files

In some circumstances, it is possible that a drawing file becomes corrupted. This can result from hardware problems or transmission errors. If a drawing file is corrupt, you might be able to recover it:

• Use AUDIT when the drawing file is open.
• Use RECOVER when you cannot open the drawing file.

If you cannot recover a drawing file, rename the drawing's .bak file to a similar name specifying a .dwg extension. If the .bak file is also corrupt, hopefully you can access a copy from a backup device or location.

Convert Legacy Objects

Drawings created in earlier releases may contain objects that have been changed or are no longer supported. Usually, when you open a drawing file created in an earlier release, objects are automatically updated to their newest version. However, there are some objects that are not automatically updated and need to be manually converted. The following lists some of the objects that you might have to convert to work as expected in the latest release:

• Hatches created and stored in a drawing file prior to AutoCAD Release 14 or AutoCAD LT 97 are less optimized, which can impact performance. The CONVERT command can be used to update hatch formats. When updating hatches, it is recommended to update hatches individually and visually verify the results are correct, as any changes to the UCS since the hatch was created could affect hatches that are rotated.
• 2D Polylines created and stored in a drawing file prior to AutoCAD Release 14 or AutoCAD LT 97 are not optimized and impact performance. The CONVERT and CONVERTPOLY commands can be used to convert "legacy" 2D polylines to lightweight polylines, which are optimized and reduce drawing file size along with improving performance.
• Lights created in AutoCAD 2006 or earlier-based products must be converted before they can be used in rendering. The CONVERTOLDLIGHTS command can be used to convert lights created in previous drawing file formats to the current format.
• Materials created in AutoCAD 2010 or earlier-based products render in the latest release but must be converted before they can be edited. The CONVERTOLDMATERIALS command can be used to convert older materials to the current materials format.

Note: The 3DCONVERSIONMODE and PLINETYPE system variables control whether lights, materials, and 2D polylines are automatically converted to their latest and optimized formats.