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618 Chapter 8: Modifiers
base Editable Patch object, except that you c annot
animate sub-objects in Edit Patch. See
Editable
Patch (page 1–950)
foraparameterreference.
Other than the inability to animate sub-objects
with Edit Patch, the main difference between
Edit Patch and Editable Patch is that t he modifier
incorporates the ability of the Surface modifier to
generate a patch object from a spline cage. For
details, see
Spline Surface (page 1–618) .
When possible, it’s far more efficient and reliable
to perform explicit editing on an Editable Patch
object rather than store those edits within the Edit
Patch modifier. The Edit Patch modifier must copy
the geometry passed to it, and this storage can lead
to large file sizes. The Edit Patch modifier also
establishes a topological dependency that can be
adversely effected if earlier operations change the
topology being sent to it.
There are, however, situations w here usi ng the Edit
Patch modifier is the preferred method.
• You want to edit a parametric object as a patch,
butwanttoretaintheabilitytomodifyits
creation parameters after the edit.
• You want to store your edits temporarily within
Edit Patch until you are satisfied with the
results, before committing them permanently
to an editable patch.
• You want to streamline your workflow w ith the
SplineSurfacetools,whichareuniquetoEdit
Patch.
• You need to make edits across several patch
objectsatonce,butdonotwanttoconvert
them to a single editable patch object.
• You have a modifier in the stack that must stay
parametric, and the resulting patch must be
edited after the modifier is applied.
Procedure
To crea te a pa tch object us ing the Cros s Secti on and
Spline Sur f ace tools:
This procedure describes how to simplify the
workflow of building objects using a spline cage
to which a patch surface is applied, a method
described in the
Surface modifier (page 1–833)
topic as “Surface Tools.”
1. Create a spline object.
Make sure that the spline ver tices form valid
three-sided or four-sided p olygons. Vertices
on splines that cross one another should be
coincident.
To ma ke sp l i n e ve r t i c e s coi n c i d e nt , d r a g
vertices over each other with 3D Snap turned
on. 3D Snap must have the Vertex or End Point
option turned on. With 3D Snap turned on,
you can snap to vertices on existing splines
as you create new splines. You can also select
vertices and use the Fuse option in an Editable
Spline to make vertices coincident.
2. Convert the spline object to an Editable Spline,
if necessary, or apply an Edit Spline modifier.
3. Use the Cross Section command in
Edit/EditableSplinetoaddsplinesconnecting
different splines in the spline object, thus
creating a spline cage.
This replaces the previous workflow of using
the CrossSect ion modifier.
4. Apply the Edit Patch modifier to the spline
object.
By default, in Edit Patch the Geometry rollout >
Spline Surface group > Generate Surface option
is on, causing the modifier to create patches
over all valid three- and four-sided polygons
in the spline cage.
This replaces the previous workflow of using
the Surface modifier.