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1088 Chapter 9: Surface Modeling
Tra nsfor ming Dependent S ub-Objects
In general, you can select and tr ansform
dependent sub-objects, but the effect of the
transform depends on the sub-object type. Some
dependent objects have a gizmo, similar to the
gizm o used with modifiers. Sub-objects that don’t
havegizmoscan’tchangerelativetotheirparent
objects. For these kinds of sub-objects, transforms
apply equally 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 g izmos, 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 1–1237) a
dependent NURBS sub-object, by default the
parent objects are also cloned. For example, if you
Shi f t +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
Shif t +Clone a
NURBS sub-object, you can also choose to remove
dependencies in order to improve performance.
Er r or Conditi on for Dependent
Sub-Objects
Sometimes changes you m ake to the parent objects
make it no longer possible to correctly update
the dependent object’s geometry. For example, a
fillet between two curves requires the curves to b e
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 c an change the error
color using the Colors panel (page 3–799) of the
Customize User Interface dialog (page 3–792).)
The arrow points to the segment indicating an error condition.
Seed Va lues
Some kinds of depen dent sub-object s depend on
geometrythatmighthavemorethanonesolution.
For example, if you want to create a surface-curve
intersection point, and the curve intersects the
surfacemorethanonce,thesoftwaremustdecide
which intersection is to be the location of the point.
For these kinds of objects, seed value (page 3–1008)
parameters control the decision. The seed location
is on a p arent object, and the software chooses the
location nearest to the seed value that satisfies the
creation condition. You can a lter the seed value
whenyoueditthesedependentsub-objects.The
seed loc ation is displayed as a yellow square.
For example, t he seed location for a sur face-curve
intersection point is a U position along the length
oftheparentcurve.Thesurface-curveintersection
closest to the seed is chosen as the loc ation of the
dependent point.
TheseedlocationforasurfaceisapairofUV
coordinates in the surface’s parameter space (page
3–988).
Replacing Parent Sub-Objects
Dependent sub-objects have controls that let
you replace the object or objects on which they
depend. For example, Offset Surface has a button