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1172 Chapter 9: Surface Modeling
U S eed a nd V S eed—
Change the UV location of
theseedvalueonthesurface.Ifthereisachoice
of projections, the projection closest to the seed
pointistheoneusedtocreatethecurve.
Vector Projected Curve rollout (modification
time)
Trim Controls group
Trim—When on, t rims the surface against the
curve. When off, the surface isn’t trimmed.
If it’s impossible to trim with this curve, the surface
is displayed in the er ror color (orange by default).
Forexample,thecurveisunusablefortrimmingif
it neither crosses the edge of the surface nor forms
aclosedloop.
Flip Trim—When on, trims the surface in the
opposite direction.
U S eed a nd V S eed—Change the UV location of
theseedvalueonthesurface.Ifthereisachoice
of projections, the projection closest to the seed
pointistheoneusedtocreatethecurve.
Replace Cur ve and Replace Sur face—Let you replace
the parent sub-objects. Click a button, then click
acurveorsurfacetoreplacetheoriginalparent
object.
CV Curv e o n Surf ace
Select N U RBS object. > Modify panel > Create Curves
rollout>DependentCurvesgroupbox>CVonSurf
button
Select NURBS object. > Modify panel > NURBS toolbox >
Create CV Curve on Surface button
A CV curve on surface is similar to a plain CV
curve,butitliesonasurface. Youcreateitby
drawing rather than project ing from a different
curve. You can use this curve type for trimming
(page 1–1080) the surface on which it lies.
Trimming a surface with a CV curve on surface
There are two methods for drawing and editing
curves on surfaces: dra wing in a viewport, or
using the Edit Curve on Surface dialog. The choice
is useful be cause you draw in two dimensions, with
a mouse or other pointing device, while the curve
on a sur face can exist in three dimensions. The
more complex the 3D surface, the more effort it
can require to create and edit a curve on a surface.
Visual feedback can help you draw the curve. The
point whose surface you first click is shown as a
blue square , and the sur face’s minimum UV point
is shown as a plus sign (+). As you draw the curve,
it is displayed interactively in viewports.
Dra wing in a Viewpor t
When you click to posit ion a CV, the click is
projected in the viewport’s Z dimension. That is,
your click is projected "through the screen" and
ontothesurface.Thisisastraightforwardwayto