116 Section 1 Introduction to Drafting
accuracy. Most CAD packages provide several
different drawing aids. These can range from a
display grid or viewport ruler to various forms
of snap. The features discussed in this section
include grid, snap, and ortho.
Grid
A display grid is a visual guideline in the
viewport, much like the lines on graph paper.
How the grid appears when displayed depends
on which CAD program you are using. For
example, AutoCAD uses dots to show the grid.
See Figure 4-19. In most CAD programs with
a grid function, you can change the density, or
spacing, of the grid.
Some CAD programs also have rulers that
can be displayed along the horizontal and verti-
cal edge of the drawing screen. The display of
these rulers is often controlled by a single com-
mand. However, the display may also be part of
an
Options
or
Settings
command, depending on
the CAD program.
AutoCAD Example:
Command: grid↵
Specify grid spacing(X) or [ON/OFF/Snap/Major/
aDaptive/Limits/Follow/Aspect] 0.5000: .25↵
Command: grid↵
Specify grid spacing(X) or [ON/OFF/Snap/Major/
aDaptive/Limits/Follow/Aspect] 0.2500: off↵f f
Command:
Snap
Snap is a function that allows the cursor
to “grab on to” certain locations on the screen.
There are two basic types of snap. These are grid
snap and object snap. A grid snap uses an invis-
ible grid, much like the visible grid produced by
the
Grid
command. When grid snap is turned on,
the cursor “jumps” to the closest snap grid point.
In most CAD programs, it is impossible to select
a location that is not one of the snap grid points
when grid snap is on. Just as with a grid, you can
typically set the snap grid density or spacing.
Figure 4-19. AutoCAD shows its grid as a matrix of dots.