9

Splines and Extended Splines 269
Lengt h—
Specifies the size of the cross–section
along the local Y axis.
Width—Specifies the size of the cross–sect ion
along the local X axis.
Angle—Adjusts the rotational position of the
cross-section in the viewpor t or renderer. For
example, if you have a square cross-sect ion you
canuseAngletopositiona"flat"sidedown.
Aspect—Sets the aspect ratio for rectangular
cross-sections. The Lo ck check box lets you lock
the aspect ratio. When Lock is turned on, Width is
locked to Leng th that results in a constant ratio of
Width to Length.
Auto S mooth—If Auto Smooth is turned on, t he
spline is auto-smoothed using the threshold
specified by the Threshold setting below it. Auto
Smooth sets the smoothing based on the ang le
between spline segments. A ny two adjacent
segmentsareputinthesamesmoothinggroupif
the angle between them is less than t he threshold
angle.
Note: Turning Auto Smooth on for every situation
doesnotalwaysgiveyouthebestsmoothing
quality. Altering the Threshold angle may be
necessary or turning Auto Smooth off may
produce the b est results.
Threshold—Specifies the threshold angle in
degrees. Any two adjacent spline segments are put
inthesamesmoothinggroupiftheanglebetween
them is less than the threshold angle.
Interpolation rollout
These settings control how a spline is generated.
All spline curves are divided into small straig ht
linesthatapproximatethetruecurve.Thenumber
of divisions between each vertex on the spline are
called steps. The more steps used, t he smoother
the cu rve appears.
Steps—Spline steps can be either adaptive (that
is,setautomaticallybyturningonAdaptive)or
specified manually.
When Adaptive is off, use the Steps field/spinner
to set the number of divisions between each vertex.
Splines with tight curves require many steps to
look smooth while gentle curves require fewer
steps. Range=0 to 100.
Optimi ze—When on, removes unneeded steps
from straight seg m ents in the spline. Optimize is
not available when Adaptive is on. Default=on.
Adaptive—When off, enables manual interpolation
control using Optimize and Steps. Default=off.
When on, Adaptive sets the number of steps for
each spline to produce a smooth curve. Straig ht
segments always receive 0 steps.
Optimized spline left and adaptive spline right. Resulting
wireframe view of eac h, res pectively, on the right.
The m ain use for m anual interpolation of splines is
in mor phing or other operations where you must
have exact control over the number of vertices
created.
Creation Method rollout