Graphics Programs Reference
In-Depth Information
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The Write Block dialog box offers a way to save parts of your current drawing as a file. As you
can see from the dialog box shown in the previous exercise, you have several options.
In that exercise, you used the Block option of the Save Location group to select an existing
block as the source object to be exported. You can also export a set of objects by choosing the
Selected Objects option. If you choose this option, the Base Point and Source Objects groups
become available. These options work the same way as their counterparts in the Define Block
dialog box, which you saw earlier when you created the Tub and Toilet blocks.
The other option in the Save Location group, Entire Drawing, lets you export the whole
drawing to its own file. This may seem to duplicate the Save As option in the File menu on the
menu bar, but saving the entire drawing from the Write Block dialog box performs some addi-
tional operations, such as stripping out unused blocks or other unused components. This has
the effect of reducing file size. You'll learn more about this feature later in this chapter.
Other Uses for Blocks
So far you've used the Create icon to create symbols, and you've used the Export and Wblock
commands to save those symbols to disk. As you can see, you can create symbols and save them
at any time while you're drawing. You've made the tub and toilet symbols into drawing files that
you can see when you check the contents of your current folder.
However, creating symbols isn't the only use for the Block, Export, and Wblock commands.
You can use them in any situation that requires grouping objects. You can also use blocks to
stretch a set of objects along one axis by using the Properties Inspector palette. Export and
Wblock also enable you to save a part of a drawing to disk. You'll see instances of these other
uses of the Block, Export, and Wblock commands throughout the topic.
Block, Export, and Wblock are extremely versatile commands, and if used judiciously, they
can boost your productivity and simplify your work. If you aren't careful, however, you can get
carried away and create more blocks than you can track. Planning your drawings helps you
determine which elements will work best as blocks and recognize situations in which other
methods of organization are more suitable.
Another way of using symbols is to use AutoCAD's external reference capabilities. External
reference files, known as
Xrefs
, are files inserted into a drawing in a way similar to how blocks
are inserted. The difference is that Xrefs don't become part of the drawing's database. Instead,
they're loaded along with the current file at startup time. It's as if AutoCAD opens several draw-
ings at once: the main file you specify when you start AutoCAD and the Xrefs associated with
the main file.
By keeping the Xrefs independent from the current file, you make sure that any changes
made to the Xrefs automatically appear in the current file. You don't have to update each
inserted copy of an Xref. For example, if you use the Insert
DWG Reference option on the
menu bar to insert the tub drawing and later you make changes to the tub, the next time you
open the Bath file, you'll see the new version of the tub.
Xrefs are especially useful in workgroup environments, where several people are working
on the same project. One person might be updating several files that have been inserted into a
variety of other files. Before Xrefs were available, everyone in the workgroup had to be notified
of the changes and had to update all the affected blocks in all the drawings that contained them.
With Xrefs, the updating is automatic. Many other features are unique to these files. They're dis-
cussed in more detail in Chapters 7 and 14.
