Chapter 1 Introduction to Three-Dimensional Modeling
3
Copyright Goodheart-Willcox Co., Inc.
Right-Hand Rule of 3D Drawing Right-Hand Rule of 3D Drawing
In order to effectively draw in 3D, you must be able to visualize objects in 3D space.
The right-hand rule is a simple method for visualizing the 3D coordinate system. It
is a representation of the positive coordinate values in the three axis directions. The
AutoCAD world coordinate system (WCS) and a user coordinate system (UCS) are
based on this concept of visualization.
To use the right-hand rule, position the thumb, index fi nger, and middle fi nger of
your right hand as shown in Figure 1-3. Imagine that your thumb is the X axis, your
index fi nger is the Y axis, and your middle fi nger is the Z axis. Hold your hand in front
of you so that your middle fi nger is pointing directly at you, as shown in Figure 1-3.
This is the plan view of the XY plane. The positive X axis is pointing to the right and
the positive Y axis is pointing up. The positive Z axis comes toward you and the origin
of this system is the palm of your hand.
The concept behind the right-hand rule can be visualized even better if you are
sitting at a computer and the AutoCAD drawing window is displayed. Make sure the
current drawing is based on the
acad.dwt
template. If the UCS icon is not displayed
in the lower-left corner of the screen, turn it on by using the
UCSICON
command, or
Figure 1-2.
A—The points making up a 2D object require only two coordinates. B—Each point of a 3D
object must have an X, Y, and Z value. Notice that the first two coordinates (X and Y) are the
same for each endpoint of a vertical line.
A B
0,4 6,4
0,4,1
6,4,1
6,4,0
6,2,0
4,2,0
4,0,0
2,0,0
0,0,0
2,0,1
4,0,1
0,2,0
0,2,1
2,2,1
4,2,1
6,2,1
6,2 4,2 2,2 0,2
0,0 2,0 4,0
X
Y
Z
Figure 1-3.
Positioning your
hand to use the
right-hand rule to
understand the
relationship of the X,
Y, and Z axes.
UCSICON
Ribbon
View
Viewport Tools
UCS Icon
Type
UCSICON