8

Dependent Sub-Objects 1089
Moving a parent sur face changes the blend surface (the
blend sur face is displayed in green)
The immediate, interactive relation between the
parent and dependent sub-objects is known as
relational modeling . Relational modeling is one
of the reasons NURBS models can be particularly
easy to change or to animate.
Impor tant: Dependent sub-objects must have
parents that are also sub-objec ts of the same NURBS
model. Dependent relationships can’t exist between
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 Impor ting 3ds Max Objec ts (page 1–1121) .
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.
Changes to the former parents don’t affect it, 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 3–836)
.)
Relational modeling does add computation time to
a model, so when you transform or edit dependent
sub-objects in other ways, often you will notice
aslowdowninperformance. Onceadependent
surface sub-object has the shape you want, you
can improve performance by making it into a
rigid
surface (p age 1–1090)
.
Tra nsfor ming Dependent S ub-Objects
In general, you c an select and transform
dependent sub-objects, but the effect of the
transform depends on the sub-object type. Some
dependent objects have a gizmo, similar to the
gizmo used with modifiers. Sub-objects that don’t
have giz mos can’t change relative to their parent
objects. For these kinds of sub-objects, transforms
apply e qually to the sub-object and its parents.
For example, moving a blend sub-object moves its
parentsaswell.Sub-objectsthathavegizmoscan
change relative to their parent objects. In this case,
as with modifiers that use gizmos, you are really
transforming the gizmo. For example, rotating a
mirror sub-object changes the mirror axis, and
therefore the mirror’s position relative to its parent
curve or surface.
When you
SHIFT+Clone (page 1–1239) a
dependent NURBS sub-object, by default the
parent objects are also cloned. For example, if you
SHIFT+Clone a UV loft, all the lofting curves are
copied as well. This means that the new object has
thesametypeastheoriginalobject.Thecloned
object keeps its parents, so you can edit it just as
you do the original. When you SHIFT+Clone a
NURBS sub-object, you can also choose to remove
dependencies in order to improve performance.
ErrorConditionforDependent
Sub-Objects
Sometimes changes you make to the parent objects
make it no longer possible to correctly update
the dep endent object’s geometry. For exa mple, a
fillet between two curves requires the curves to be
coplanar. If you move one curve (or its CVs or
points)sothatthecurvesarenolongercoplanar,
thefilletcannotupdatecorrectly.Inthiscase,the
dependent object’s geometry reverts to a default
position, and it is displayed in orange to indicate
an error condition. (You can change the error
color using the
Colors panel (page 3–843) of the
Customize User Interface dialog (page 3–836) .)