Graphics Programs Reference
In-Depth Information
Normals
nor
mal
adj.
4.
Mathematics
a.
Being at
right angles; perpendicular. (
The American
Heritage Dictionary
)
“Abby...someone ...”
“Abby
who
?”
“Abby... Normal.”
— Igor and Dr.
Frankenstein,
Young Frankenstein
Figure 3-5: The direction a polygon is facing is indicated by the dashed line
rising perpendicular from its surface. This dashed line is known as the surface
normal.
Surface normals tell LightWave which
direction a polygon is facing. If a polygon is
facing
away
from its viewer, it is treated as
“invisible,” like the polygon on the right in
the shaded Perspective window in Figure
3-5.
You can tell the specific surface on a
polygon to be visible from either side by
setting its Double Sided surface attribute
(
Surface Editor | Double Sided
). The
reason this attribute isn't active by default
is that most objects are really only seen
from one side, the
outside
— like a basket-
ball or a jet fighter. So LightWave
culls
the
back side of its surfaces by default to speed
its displays and its rendering. (
Elegance
—
If you aren't going to see something, don't
bust your chops on it!)
Note
You can use the fact that unless you specifi-
cally tell a surface to be treated as
double
sided
, it is “invisible” from its back side when
rendering interior sets. You won't be limited
to placing your camera inside the set. You
can have your camera positioned outside
your set, facing in, and if the walls of your
set aren't double-sided, you'll be able to see
right through them!
