Graphics Programs Reference
In-Depth Information
FIGURE 22.8
The bracket so far,
with hidden lines
removed
As you learned in the earlier chapters in Part 4, Wireframe views, such as the one in the pre-
vious exercise, are somewhat difficult to decipher. Until you use the Hide command (View
Hide), you can't be sure that the subtracted cylinders are in fact holes. Using the Hide command
frequently will help you keep track of what's going on with your solid model. You can also use a
visual style like Hidden or Shades Of Gray.
You may also have noticed in step 4 that even though the cylinders were taller than the open-
ing they created, they worked fine to remove part of the rectangular solid. The cylinders were
1.5 units tall, not 1 unit, which is the thickness of the bracket. Having drawn the cylinders taller
than needed, you saw that when AutoCAD performed the subtraction, it ignored the portion of
the cylinders that didn't affect the bracket. AutoCAD always discards the portion of a primitive
that isn't used in a subtract operation.
USING 3D SOLID OPERATIONS ON 2D DRAWINGS
You can apply some of the features described in this chapter to 2D drafting by taking advantage
of AutoCAD's region object.
Regions
are two-dimensional objects to which you can apply Boolean
operations.
The following illustration shows how a set of closed polyline shapes can be quickly turned into
a drawing of a wrench using regions. The shapes at the top of the figure are first converted into
regions using the Region tool on the Closed Shapes tool group. Next, the shapes are aligned, as
shown in the middle of the image. Finally, the circles and rectangle are joined with the Union
command (type
UNI
↵); then, the hexagonal shapes are subtracted from the combined shape (type
SU
↵). You can use the Region.dwg sample file if you'd like to experiment.
Create closed polyline
shapes and convert
them to regions.
Move the shapes
into position to lay
out the object.
Use the Union and
Subtract commands
to create the final object.
