Xrefs are frequently used to import large drawings for reference or backgrounds. Multiple Xrefs, such as a floor plan, column grid layout, and site plan drawing, might be combined into one file. One drawback to multiple Xrefs in earlier versions of AutoCAD is that the entireXref is loaded into Jllemory, even if only a small portion of the Xref is used for the final plotted output. For computers with limited . resources, multiple Xrefs could slow the system to a crawl. AutoCAD 2000 offers two tools that help make display and memory use more efficient when using Xrefs: The Xclip command and the Demand Load option in the Options dialog box.
Xclip is the name of a command accessed by choosing Modify :> Clip >Xref. This command allows you to clip the display of an’ Xref or block to any shape you desire as shown in Figure 6.14. For example, you may want to display only an L-shaped portion of a floor plan Io be part of your current drawing. Xclip lets you define such a view.
Blocks and multiple Xrefs can be clipped as well. And you can specify a front and back’clipping distance so that visibility of objects in 3D space can be controlled (see Using 3D Features to TrickAutoCAD in this chapter). You can define a clip area using polylines or spline curves, although curve-fitted polylines will revert to decurved polylines. (See Chapter 13 for more on polylines and spline curves.)
Controlling Xref Settings in the Options Dialog Box
The External Reference button group in the Open and Save tab of the Options dialog . box offers some tools to help y~u manage memory use and other features related to Xrefs. If you’re working on large projects with others in a workgroup, you’ll want to . be aware of these settings and what they do.
The Demand Load Xref drop-down list offers three settings: Disabled, Enabled, and Enabled with Copy. Demand Load is enabled by default in the standard AutoCAD drawing setup. Besides reducing the amount of memory an Xrer consumes, Demand Load also prevent other users from editing the ~f while it is’being viewed as part of your current drawing. This is done to help aid drawirl version control and drawing management. The third Demand Load option. Enabled . with’ Copy, creates a copy of the source Xref file, and then uses the copy, thereby allowing other autoCAD users to edit the source Xref file.
Demand improves performance by loading only the parts of the referenced drawing that are needed to regenerate the current drawing. You can set the location for the Xref copy in the Files tab of the Options dialog box under Temporary External Reference File Location.
Two other options are also available in the Options dialog box. Retain Changes to Xref-Layers Instructs AutoCAD to remember any layer color or visibility settings of Xrefs from one editing session to the next. In the standard AutoCAD settings, this option is on by default Allow Other Users to Refedit Current Drawing Lets others edit the current drawing using the Modify> In-Place Xref and Block Edit> Edit Reference command (Refedit), You’ll learn about this command in the next section.
Editing Xrefs In Place
option in the Modify pull-down menu. This option issues the Refedit command.
The following exercise demonstrates how Refedit works.
1. If it isn’t already open, open the Pl anx ref. dwg file..
2. Zoom intothe Unit plan in the lower-left comer of the drawing so you see a view similar to Figure 6.15.
3. Choose Modify> In-Place Xref and Block Edit> Edit Reference from the menu bar ..
4. At the Se1ect reference: prompt, click the kitchenette in the comer unit.
The Reference Edit dialog box appears.
5. The Reference Edit dialog box contains two windows, The right-hand window shows- the entire Xref that you “are editing. The window to the left shows a listing of the specific item you selected in the Xref. Notice that the Ustlng ‘shows the hierarchical relationship of the kitchenette block.in relation to the Unitxref Xref. ‘
6. In the left-hand window, click the Kitchen listing, then click OK. The Reference Edit dialog box disappears. ..
7. Use a selection window to select the entire.1ower-left comer unit. Notice that only the kitchenette is highlighted while all other objects become gray.
8. Press.J. The Refedit toolbar <lppears. You C,1I1 now edit the kitchenette.
Command isolates the objects you select in step 7 for editing. You cannot edit anything else until you choose Modify In-Place Xref and Block Edit Save Reference Edit or Modify. In-Place Xref and Block Edit> Discard Reference Edit from the menu bar.
Note that at this point, you are actually able to edit a block within an Xref. Now let’s continue editing the kitchenette.
1. Zoom in on the kitchenette, then move the four burners to the right 8 inches (20cm for metric users).
2. Erase the sink.
3. Click the Save Back Changes to Reference button on the Refedit toolbar
5. z.oom back to your previous view. Notice that the other units now reflect the changes you made to the Unitxref Xref.
6. Open the Unitxref. dwg file. Notice that the kitchen now changes you made to the Xref of the unit in the Planxref file. This 51, that by choosing to save the reference edit in step 3, you actually ,the (1 back to the Xref’s source file.
As you saw from these two exercises, you can actually edit a specific block within an Xref, but you must click that block when you are prompted to select objects at the beginning of the Refedit command.
The Reference Edit dialog box offers you the option to isolate the block itself, or select the,bject up in the block /Xref hierarchy. You can also cycle through the hierarchy using the Next button just below the hierarchy listing.
In these exercises, you edited a block contained within an Xref, but you could have just as easily edited a single block or a block nested inside another block. Changes in blocks will not affect other files, however. The changes remain within the current file until you explicitly export the changed block to a file, as you saw is, earlier exercises.