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1140 Chapter 9: Surface Modeling
Wa rning: When you break a curve sub-object, you lose
the animation controllers for all points or CVs on the
curve.
Join—
Joins two curve sub-objects together. After
you have joined the curves in a viewport, the Join
Curves dialog (page 1–1232) is displayed. This
dialog lets you choose the method for joining the
two curves.
Wa rning: When you join two curve sub-objects, you
lose the animation controllers for all points or CVs on
both curves.
Mater ial ID—
LetsyouassignamaterialIDvalue
to the curve. If the curve is renderable, material
IDs let you assign a material to the curve using
a Mult i/Sub-Object (page 2–1594) mater ial. In
addition, the Select by ID button lets you select a
curveormultiplecurvesbyspecifyingamaterial
ID number. Can range from 1 to 100. Default=1.
Select by ID—Displays a Select by Material ID (page
1–1238) dialog.
CV Curve rollout
This additional rollout is displa y ed when a CV
cur ve is selected.
Degree—Setsthedegreeofthecurve.Thehigher
the degree value, the greater the continuit y. The
lower the degree, the more discontinuous the
cur ve segments b ecome. The deg ree can’t b e less
than one or greater than the number a llowed by
the number of CVs in t he curve. Degree 3 curves
are adequate to represent continuous curves, and
arestableandwellbehaved.Default=3.
Setting the degree greater than 3 isn’t
recommended because higher-degree curves are
slower to calculate and less stable numerically.
Higher-degree curves are supported primarily to
be compatible with models created using other
surface modeling programs.
The number of CVs in a CV cur ve must be at least
onegreaterthanthecurve’sdegree.
Automatic Reparam e ter ization group
The controls in this group bo x let you specify
automatic reparameterization. They are similar
to the controls in the Reparameterize dialog (page
1–1237), with the addition that all choices except
for None tell the software to reparameterize the
curve automatically; that is, whenever you edit it
by moving CVs, refining, and so on.
None—Do not reparameterize automatically.
Chord L e n g t h —Cho o ses the chord-length
algorithm for reparameterization.
Chord-length reparameterization spaces knots (in
parameter space (page 3–988)) based on the square
rootofthelengthofeachcurvesegment.
Chord-length reparameterization is usually the
best choice.
Unifor m—Spaces the knots uniformly.
A uniform knot vector has t he advantage that the
curve or surface changes only locally when you edit
it. W ith chord-length parameterization, moving
any CV can potentially change the entire curve.
Clo se—Closesthecurve.Disabledifthecurveis
already closed.
Rebuild—Displays the Rebuild CV Curve dialog
(page 1–1236), which lets you specify how to