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Dependent Sub-Objects 1087
them are required to lie on the curve or surface.
Unlike CVs, points do not have a weight.
Point curves and point surfaces can be more
intuitive to create and work with. However ,
workingwithpointsub-objectsisslowerthan
working with CV sub-objects. You can think of a
point curve or point surface as being dependent
on the points to which it fits.
Points that you create individually are the same as
the points on point curves and surfaces, except that
initially they aren’t part of a curve or surface. You
cancreateapointcurvebyfittingittopointsthat
you select. When you fit the new point curve, you
can u se points that are part of curves or surfaces,
and individual point sub-objects.
Dependent S ub-Objects
NURBS sub-objects are either independen t or
dependent. A dependent sub-object is based on
the geometr y of other sub-objects. For example,
a blend surface smoothly connects two other
surfaces. Transforming or animating either of
the original, parent surfaces causes the shape of
the blend to change as it maintains a connection
between the parents.
Moving a parent surface changes the blend surface (the blend
surface i s d ispla yed in green)
The immediate, interactive relation be tween the
parent and dependent sub-objects is known as
relational modeling. Relational modeling is one of
the reasons NURBS models can be part icularly
easy to change or to animat e.
Impor tant: Dependent sub-objects must have
parents that are also sub-objects of the same NURBS
model. Dependent relationships can’t exist bet ween
object-level NURBS curves or surfaces. If you want to use
a top-level NURBS object to create a dependent object,
first you must attach or import the top-level object. See
Attaching and Importing 3ds Max Objects (page 1–1120).
You have the option of making a dependent
sub-object independent. After you do so, the
sub-object is no longer related to its parents.
Changestotheformerparentsdon’taffectit,but
you can edit and transform it as an independent
sub-object in its own right.
At the appropriate sub-object level, dependent
NURBS are displayed in green in wireframe
viewports. (You can change the display color using
the Colors panel of the Customize User Interface
dialog (page 3–792).)
Relational modeling does add computation time to
a model, so when you transform or edit dependent
sub-objects in other wa ys, often you will notice
aslowdowninperformance. Onceadependent
surface sub-object has the shape you want, you
can improve per formance by making it into a rigid
surface (page 1–1089).