8

1122 Chapter 9: Sur face Modeling
• To maintain parametric control over primitives.
For example, if you import a sphere, you can
change its radius directly, which you can’t do
after using Attach.
• TouseBeziersplinesasNURBScurves.
For example, if you want to use a Bezier spline
asacurveinaNURBSmodel,importit.This
allows you to edit it as a Bezier spline, and not
as a NU R BS curve.
Surfaces and curves created by an import are
available in the NURBS model. For example, if
you import a box, you can create a blend surface
between one of its polygons and another surf ace
in your NURBS object.
Once you have imported an object, the NURBS
object has an Imports sub-object level. When you
select an import, it is highlighted in red.
Itisanerrortoapplyamodifiertoanimportwhen
the modifier conver ts the import into something
that can’t be converted to a NURBS object. For
example, if you import a sphere and apply a
Bend
(page 1–541)
to it, the sphere con v erts to an
editable mesh, which can’t automatically convert
to a NURBS surface. In this case, the import
sub-object is in an error state, and it is displayed in
the error color (orange by default).
Imports are displayed in two different ways.
WhileyouworkattheNURBSobjectlevelorata
sub-object level other than Imports, imports are
displayed as NURBS curves or surfaces, and use
the NURBS object’s mesh tessellation (see
Surface
Approximation (page 1–1241)
). However, at the
Imports sub-object level, the selected import is
displayed using its native display format. In other
words, it displays as it would if it were a top-level
object.Thisisbecausethedisplaymustletyouedit
the imported object. For example, an imported
Bezier spline needs to display its tangent handles.
This wouldn’t be possible if it were displayed as
a converted NURBS curve. Leaving the Imports
sub-object level returns to NURBS-style display.
You can extract an imported object. This creates
an independent, top-level object again.
Procedures
To a tta ch or import a n obj ect to a NUR B S obj ect:
1.
Select the NURBS object and go to the
Modify panel.
2. (Optional.) Turn on Reorient if you want to
reorient and align the import with the center
of the NURBS object.
3. Turn on Attach or Import.
Note: At this step, you can click Attach Multiple
or Import Multiple instead. These buttons
display a select-by-name dialog so you can
choose multiple objects to attach or import.
4. Click the object to attach or import.
The mouse cursor changes shape to indicate
avalidobject.Youcanattachcurves,NURBS
surfaces, or objects convertible to NURBS.
To ex tr a ct an imported obj ect:
1.
Go to the Imports sub-object level and select
the object to extract.
2. Click Extract Import on the Import sub-object
rollout.
If Copy is set (the default), the extrac ted object
is a top-level copy of the imported object.
If Instance is set, the extracted object is an
instance of the imported object. Initially the
extracted object occupies the same space as the
imported object: you must move either the
extrac ted object, the import sub-object, or the