Modifying at Sub-Object Level

In a row of column sub-objects, a single column has been modified at the sub-object level.

To achieve highly detailed modeling effects, you can directly transform, modify, and align the geometry of objects at the sub-object level.

Sub-objects are the pieces that make up objects, such as vertices and faces. You can also access and transform the sub-object components of modifiers.

The particular geometry available at sub-object level depends on the object type. See Edit Modifiers and Editable Objects for details on each object type.

Making a Sub-Object Selection

These are the general steps in setting up an object for sub-object selection. See Edit Modifiers and Editable Objects for more information.

Convert the object into an editable object such as an editable mesh, editable spline, editable poly, and so on. (Some modifiers you can apply to the object, such as Mesh Select or Spline Select, also have sub-object levels.)
Tip: Work in a wireframe viewport so you can see the geometry.
On the modifier stack display, click the plus icon to the left of the name of the modifier or editable object. This expands the object's hierarchy, showing the names of the sub-object levels at which you can work.
On the stack display, choose the kind of sub-object geometry you want to work with: for example, Vertex, Face, or Edge. Each sub-object selection level has rollouts with their own sets of options.
The sub-object level highlight is yellow by default.
Use standard selection techniques to select sub-object geometry, from a single sub-object to the entire object. By default, the sub-object selection highlights in red.

Once you make a sub-object selection of geometry, you can do any of the following:

Apply any options supplied for the kind of object and the selection level.
Apply standard transforms (move, scale, rotate). See Transforming a Sub-Object Selection (below).
Apply object-space modifiers (Bend, Taper, and Twist, for example) to perform useful modeling operations.
Bind a space warp to the selection. The rest of the object is unaffected by the warping.
Use the toolbar commands Align, Normal Align, and Align To View with face selections.

Transforming a Sub-Object Selection

Using an editable mesh, poly, patch, or spline, you can directly transform any sub-object selection. However, Mesh Select and Spline Select enable only selection.

To transform a sub-object selection made with a Select modifier:

Add an XForm modifier to the stack, following (or somewhere above) the Select modifier.
In the stack, open the Select modifier and make a sub-object selection.
Choose XForm in the stack. You then transform the XForm gizmo, which applies the transform to the selection.

Selecting and Transforming Modifier Components

Most modifiers have sub-object components, such as a gizmo and center. Like sub-object geometry, these components can be accessed and transformed at sub-object level, directly modifying the object’s shape.

Other modifiers, like those for free-form deformation, have control points and lattices at a sub-object level. Moving these components creates the modeling effects of the modifier.