Edit Patch Modifier

Command entry:Create or select an object

Modify panel

Modifier List

Object Space Modifiers

Edit Patch

Command entry:Create or select an object

Modifiers menu

Patch/Spline Editing

Edit Patch

The Edit Patch modifier provides editing tools for different sub-object levels of the selected object: vertex, handle, edge, patch, and element. The Edit Patch modifier matches all the capabilities of the base Editable Patch object, except that you cannot animate sub-objects in Edit Patch. See Editable Patch for a parameter reference.

Other than the inability to animate sub-objects with Edit Patch, the main difference between Edit Patch and Editable Patch is that the modifier incorporates the ability of the Surface modifier to generate a patch object from a spline cage. For details, see Spline Surface.

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 where using the Edit Patch modifier is the preferred method.

You want to edit a parametric object as a patch, but want to retain the ability to modify its 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 with the Spline Surface tools, which are unique to Edit Patch.
You need to make edits across several patch objects at once, but do not want to convert 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.

Procedures

To create a patch object using the Cross Section and Spline Surface 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 topic as “Surface Tools.”

Create a spline object.
Make sure that the spline vertices form valid three-sided or four-sided polygons. Vertices on splines that cross one another should be coincident.

To make spline vertices coincident, drag 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.
Convert the spline object to an Editable Spline, if necessary, or apply an Edit Spline modifier.
Use the Cross Section command in Edit/Editable Spline to add splines connecting different splines in the spline object, thus creating a spline cage.
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.
Adjust the Spline Surface settings and edit the object as necessary. If you modify the spline object, for best results, edit at the Vertex sub-object level, and be sure to select all vertices at an intersection before moving them.

Interface

Spline Surface group

The Geometry rollout Spline Surface group is found only in the Edit Patch modifier; it's not available in the Editable Patch object. The group becomes available when the object to which the Edit Patch modifier is applied consists of splines. Its controls replicate the functionality of the Surface modifier.

For best results, apply the Spline Surface controls after creating a spline cage with the CrossSection modifier or the Editable Spline Cross Section command. The latter approach approximates the Surface Tools workflow (described in the Surface Modifier topic), but with a simpler modifier stack; instead of additional CrossSection and Surface modifiers, the stack need contain only an Editable Spline object and an Edit Patch modifier. Alternatively, you can use the Edit Spline modifier's Cross Section command.

Generate Surface: Creates a patch surface using existing splines to define the patch edges. Default=on.
Threshold: Determines the overall distance that is used to weld the vertices of the spline object. All vertices/vectors within the threshold distance of each other are treated as one. Threshold uses units set in the Units Setup dialog. Default=1.0.

NoteSpline control handles are also treated as vertices, so setting high Threshold levels can produce unexpected results.
Flip Normals: Reverses the facing direction of the patch surface. Default=off.
Remove Interior Patches: Removes interior faces of an object that you would not normally see. These are the faces created within the caps or other interior patches of the same type of a closed polygon. Default=on.
Use Only Selected Segs: Only segments selected in the Edit Spline modifier or the editable spline object will be used by the Surface modifier to create patches. Default=off.

NoteSegment Sub-Object does not have to be left on in the Edit Spline modifier or editable spline object.