118 Section 1 Introduction to Drafting
Colors and Linetypes
Another important “management” aspect
of CAD programs is object display color. At a
very simple level, object display colors help to
visually catalog the objects in a drawing. For
example, if all objects in a drawing are displayed
in the same color, it can be hard to identify the
individual features. On the other hand, if all
dimension lines are displayed in red, object
lines are displayed in green, and all symbols are
displayed in yellow, at a glance anybody who is
familiar with this color scheme can determine
what is represented. Just as with layer names, it
is important to adopt a color usage convention
and make sure everybody follows it.
Often, object display colors are determined
by the layer on which they are drawn. This is one
reason that layer conventions are so important,
as described in the previous section. However,
most CAD programs allow you to “override”
this setting and assign a specifi display color to fic
an object, regardless of which layer it is on. The
command used to change an object display color
can be
Change, Color,
r r
Properties, or another com-
mand. The exact command will be determined
by the CAD program you are using.
Managing the types of lines used on a
drawing is also important. Fortunately, there is
an almost universally accepted practice for rep-
resenting lines. This practice is the Alphabet of
Lines. The Alphabet of Lines is covered in detail in
Chapter 2. You should always follow the Alphabet
of Lines. Just because you use CAD to create a
drawing does not remove your responsibility to
follow this practice. Most CAD programs provide
several linetypes that conform to the Alphabet of
Lines. You can typically adjust the scale of each
line (or all lines) so your particular application
better conforms. Do not let the ease at which lines
can be drawn “slide” into bad drafting habits.
Always follow the Alphabet of Lines.
As with colors, most CAD programs allow
you to assign linetypes to individual objects.
You can also generally assign a linetype based
on which layer the object is currently “residing”
on. While the Alphabet of Lines provides clear
direction on which linetypes to use, be sure to
develop a convention based on how the linetypes
are assigned. Choose to assign linetypes “by
layer” or “by object,” or some combination of the
two, and then be sure everybody follows that
convention.
Blocks and Attributes
Blocks are special objects that can best be
thought of as symbols inserted into a drawing.
Most CAD systems support blocks. In addition,
in most CAD systems, the block function sup-
ports a feature called attributes. An attribute is
text information saved with the block when it is
inserted into a drawing. For example, you may
create a block that consists of all lines you would
normally draw to represent a case-molded win-
dow. In addition to creating the block, you assign
attributes to the block describing the window
size, style, and manufacturer. See Figure 4-20A.
Figure 4-20. A—This window block contains attributes, which have values assigned. B—The AutoCAD command
sequence for inserting the block and assigning attribute values.
A B
Command: INSERTˆ
(In the
INSERT
dialog box, pick the block)
Specify insertion point or
[Basepoint/Scale/Rotate]:
(specify an insertion point)
Enter attribute values
Enter window width 36":ˆ
Type manufacturer name GlazRus:ˆ
Enter wood or vinyl Wood:ˆ
Command: