Graphics Programs Reference
In-Depth Information
Figure 1-2: Heading (H) rotates around the
Y axis
.
Pitch (P) rotates around the
X axis
. Bank (B) rotates
around the
Z axis
.
Figure 1-1: The convention for defining
three-dimensional space.
with negative values, and space to the right
of X=0 is measured with positive values.
Space “away from you” is measured with
positive values of the Z axis, and space
“toward you” is measured with negative
values of the Z axis.
Bear in mind that like the image in Fig-
ure 1-1, your
viewport
(your window into
this “virtual world,” of which you may have
more than one open) may be offset from
what the computer considers “world-
space.”
World-space
is easy to think of as
LightWave's “handle” on its reality. No mat-
ter how you spin an object, no matter how
you rotate a viewport, LightWave will
always keep X=0, Y=0, and Z=0
exactly
where it always has been (and forever will
be). So, like in Figure 1-1, the viewport can
be rotated counterclockwise a bit and tilted
up just a bit so you can see the axes all
nicely laid out before you, but LightWave's
handle on where +X becomes -X will
never vary.
For keeping track of how an object is
rotated within three-dimensional space,
LightWave has taken its labels for the rota-
tion axes from what you'd think of while
flying a plane:
H
eading,
P
itch, and
B
ank.
Figure 1-2 is probably confusing. Let me
take a different angle on the concept.
If you think of your hand like an airplane
(I know it's simplistic, but bear with me),
heading is the axis that would change your
compass direction, pitch is the axis that
would raise and lower the nose of the air-
plane, and bank is the axis that would get
the plane to roll on its side. It may seem
silly, but for the first couple of years that I
worked in 3D, I still did the “my-hand-is-
an-airplane” thing to figure out rotation
axes. (Hey, if it works, don't knock it!)
