170 Exploring Drafting
The Extend command is used to extend
lines and arcs to meet other objects. After
entering the command, a boundary edge
must be specified. This represents the point to
where the object is extended. Next, the object
to be extended is selected. The object is then
extended to the boundary to create a larger
entity. As with the Trim command, you can
select as many cutting edges and objects as
needed to complete the extend operation.
Using Display Commands
There are a variety of ways to display
drawing content on screen when working on
a CAD drawing. Display commands are used
to change the magnification of the drawing,
change the viewpoint, and establish drawing
views, such as the views in a multiview
drawing. Multiview drawings are discussed
in Chapter 9.
When working on a CAD drawing, it
is often necessary to “zoom” into certain
portions to view features. TheZoomcommand
provides this capability. After entering the
command, you can zoom into a portion of the
drawing by windowing around the display.
The windowed portion is then shown at a
greater magnification scale. You can also
enter a magnification scale factor to reduce
or enlarge the display relative to the current
display. A third option allows you to zoom
the view in real time by using the pointing
device to move the cursor upward (to enlarge
the view) or downward (to reduce the view).
When you want to move the drawing
across the screen to view areas outside of the
current display without changing the magnifi- fi
cation, youcanusethePancommand.Panning
adjusts the view in real time. The drawing is
panned by using the pointing device to move
the cursor in the direction desired.
More advanced viewing commands are
available with 3D drawing programs. While
command names and navigation methods
will vary, 3D viewing commands typically
allow you to rotate a 3D model in three
dimensions by using the pointing device.
The view is changed in real time, allowing
you to view different features across the
model dynamically.
Using Measurement, Object
Property, and Drawing
Status Commands
During the drawing process, it is common
to check measurements of existing objects
to verify accuracy and confirm that design
requirements are met. Measurements are also
needed to determine the correct dimensions
when constructing new features in relation
to other features. CAD programs typically
provide commands to make measurements
of existing objects and determine other infor-
mation, such as object properties and current
drawing fi le data.
Measurement commands allow you to
quickly determine common measurements,
such as linear distances and area and perim-
eter calculations. The Measure Geometry
command allows you to select two points and
measure the distance and/or angle between
them. You can also use this command to
determine the radius or diameter of a circle
or arc by selecting the object. When using the
Measure Geometry command to determine
the area or perimeter of a closed object or a
specifi area, you must select the object or fic
pick the points defining the area.
Common object properties, such as
layer and linetype settings, can be identi-
fi ed by using the fi Properties command. After
entering the command and selecting an
object, the program displays various informa-
tion, including the object coordinates and the
layer, linetype, and color settings assigned to
the object.
Other commands are available for deter-
mining additional information about objects
in the current drawing and data associated
with the drawing file. The fi List command
allows you to select one or more objects and