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1146 Chapter 9: Surface Modeling
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 deg ree greater than 3 isn’t
recommended because higher-degrees are
slower to calculate and less stable numerically.
Higher-degrees are supported primarily to be
compatible with models created using other
surface modeling programs.
The number of CVs in a given dimension must be
at least one g reater than that dimension’s degree.
Automatic Reparameterization group
The cont rols in this group box let you specify
automatic reparameterization. They are similar
to the controls in the Repar ameterize dialog (page
1–1237), with the addition tha t all choices except
for None tell the software to reparameterize the
curve automatically; that is, w henever 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 surface.
The close controls let you close a surface. They
aredisplayedontheCVSurfacerolloutwhilean
independent CV surface sub-object is selected.
They are disabled if the surface is already closed in
that direction.
Close R ows —Closes the surface by joining the ends
of its rows.
Close Cols.—Closes the surface by joining the ends
of its columns.
Rebuild—Displays the Rebuild CV Surface dialog
(page 1–1236), which lets you specify how to
rebuild the surface. Rebuilding the surface can
change its appearance.
Wa rn in g : When you rebuild a surface, you lose th e
animation controllers for all CVs on the surface.
Reparam.—
Displays the Reparameterize dialog
(page 1–1237). Reparameterizing a surface
changes the surface’s parameter space (page 3–988)
to prov ide a b e tter relation between control point
locationsandtheshapeofthesurface.
Tip: It is a good idea to reparameterize after you
have added CVs to the surface by refining or
inserting.
Wa rn in g : When you reparameterize a surface, you lose
the animation controllers for all CVs on the surface.