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1180 Chapter 9: Surface Modeling
doesn’t change as you edit it, and can become
irregular.
None—Do not reparameterize.
Cho rd Le n g t h —Chooses the chord-length
algorithm for reparameterization.
Chord-length reparameterization spaces knots (in
parameter space (page 3–988)) based on the square
root of the length of each curve segment.
Chord-length reparameterization is usually the
best choice.
Unifor m—Spaces the knots uniformly.
A uniform knot vector has the advantage that the
surface will change only locally when you edit it.
With the other two forms of parameterization,
moving any CV can change the entire surface.
CV Surface rollout (modificatio n time)
U Degree a nd V Degr ee—Letyousetthedegreeof
the surface in either the U or V dimension. The
higher the degree va lue, the g reater the continuity.
Thelowerthedegree,themorediscontinuousthe
surface segments become. The degree can’t b e less
than one or greater than the number allowed by the
number of CVs in the specified dimension. Degree
3 is adequate to represent continuous surfaces, and
is stable and well behaved. Default=3.
Setting the degree greater than 3 isn’t
recommended, because higher degrees are slower
to calculate and less stable numerically. Hig her
degrees are suppor ted primarily to be compatible
with mo dels created using other surface modeling
programs.
The number of CVs in a g iven dimension must b e
at least one greater than that dimension’s degree.
Automatic Reparam e ter ization group
The radio buttons in this group box let you
choose automatic reparameterization. With
reparameterization, the surface maintains
its parameteri zation as you edit it. Without
reparameterization, the surface’s parameterization
doesn’t change as you edit it, and can become
irregular.
None—Do not reparameterize.
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
surface will change only locally when you edit it.
With the other two forms of p a rameterization,
moving any CV can change the entire surface.
The close controls let you close a surface. They
appear on the Point Surface rollout while an
independent p oint surface sub-object is selected.
They have no effect if the surface is already closed
in that dir ection.
Close R ows —Closes the surface by joining the ends
of its rows.