XREF is a great way to quickly and easily connect
information from drawing to drawing.
Many users find it daunting, cumbersome, or just simply confusing. Let's take a closer look.
An XREF (eXternal REFerence) is an external CAD file, image,
or PDF that is linked to your current drawing.
AutoCAD loads the file into the current drawing and displays it, and
even notifies you if a referenced file has been modified, and prompts you to
reload the reference. You can think of
XREFs as blocks from another drawing.
XREFs have several benefits:
- Multiple drawings can reference the same file, so updating is easy, and more than one user can access the same data.
- Layer settings for XREF drawings can be easily manipulated.
- Since all that is tracked is the insertion, rotation and scale factor, XREFs do not add much to the size of a file.
- An XREF is like a block, if you freeze the layer it is inserted on, the entire XREF is frozen.
- When the reference file is modified, all the drawings that have it are updated.
- 5 types can be XREFed: DWG, DXF, DGN (yes, Microstation files!), PDF (yes, PDF files too!), and image files (JPG, GIF, TIF, PNG, .
Types
of XREFs
There are 2 types of XREF: Attachment and Overlay, which you
specify in the XREF attach dialog.
Attachment means
the file AND all of its XREFs get attached to when XREFed into another drawing.
Overlay means only the
selected file gets referenced when XREFed to another drawing; AutoCAD ignores
the XREFs that the file may have (no nested references).
To change from one to the other, toggle it in the Details
area of the XREF Palette.
Example: You have a drawing of a site, with a pipeline XREF
as Overlay. If the site drawing gets XREFed into another drawing, the pipeline
will not display, since overlays do not nest.
Visretain controls the appearance of XREF layers in
your drawing. If set to 1, any changes to XREF layer
properties, visibility, colour, etc is saved in the host file. When visretain
is set to 0, all layer settings get reset from the XREF each time the file is
loaded or reloaded.
Path
and Status
Loaded:
The reference is loaded into
the current drawing
Unloaded:
The reference is not loaded, but
AutoCAD still has the info, and can easily reload it.
Orphaned: The reference is nested in another
reference that has been unloaded. Orphaned references do not display.
Not Found: AutoCAD cannot locate the reference
file.
Unreferenced: The XREF has been erased from the drawing
file, but not detached as an XREF. AutoCAD knows where to find the XREF, but
not where it is inserted.
The XREF path can be set as either relative, full, or
none. AutoCAD saves either the full path
(drive name, directory structure, file name), relative path (the location of
the XREF relative to the host drawing, file name), or none (just the file
name).
TIP#1: If you want to know what layer, linetype, etc,
an object on an XREF is, use the command XLIST: it returns object information
without opening the XREF file!
TIP #2: NCOPY allows
copying of selected objects in an XREF directly into your drawing!
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