Affect Region Modifier

The Affect Region modifier is a surface modeling tool, primarily used with vertex sub-object selections while surface modeling. With Affect Region, transforming a selection of vertices can also transform vertices in the region that surrounds the selection. This can help you form a bubble or indentation in the surface of an object. The easiest way to see this modifier's effect is with a shallow, flat box object with plenty of subdivisions. The Affect Region modifier has a two-part, arrow-shaped gizmo, plus numeric controls.

Modify panel > Make a vertex sub-object selection. > Modifier List > Object-Space Modifiers > Affect Region
Standard menu: Make a vertex sub-object selection. > Modifiers menu > Parametric > Affect Region
Enhanced menu: Make a vertex sub-object selection. > Modifiers menu > Geometry (Parametric) > Affect Region

When you apply the Affect Region modifier, it assigns an arrow-like gizmo consisting of two points connected by a line. The base of the arrow is the start point. The length and direction of the arrow defines the amount of movement of the vertices. Any vertices within Falloff distance of the base of the arrow are translated in the direction of the arrow.

Because no points on the mesh are directly selected, this modifier doesn't depend on the topology of the input object. You can apply it to any renderable object. However, you can limit the effect by using a selection modifier like Mesh Select or Volume Select to pass a sub-object selection up the stack.

Note: The Affect Region modifier is ideal for simple animated effects, especially when you need to use interactive parameters. However, for fine-tuned modeling, you'll probably prefer the expanded capabilities of Soft Selection in Editable Mesh, Editable Poly, Edit Mesh, Mesh Select, Volume Select, the HSDS modifier, and NURBS.

Affect Region modifier applied

Procedures

Example: To form a bubble over the surface of a plane:

Create a plane with 15 width and length segments.
Set the length and width of the plane to 50 units.
Apply the Affect Region modifier.
In the Parameters group, set Falloff to 50.
Adjust the parameters to achieve different effects.

Interface

Note: The parameters of this modifier are similar to those of the Soft Selection function of an Editable Mesh.

Modifier Stack

Point sub-object level

At this sub-object level, the base and tip of the gizmo arrow are points that can be selected. You can select, translate, and animate these two points together or individually.

For more information on the stack display, see Modifier Stack.

Parameters rollout

Parameters group

Falloff: Sets the radius of affected vertices, in units, from the base of the gizmo arrow. (Spinner value range: float, 0.0 to 999,999.0)
Ignore Back Facing: Affects only those vertices whose face normals are in the same general direction as the gizmo arrow. When turned off, all vertices in the Falloff group are affected.

Curve group

Pinch: Affects the tangency of the curve where it meets the arrow tip. Positive values produce a pointed tip while negative values produce a dimple. (Spinner value range: float, –999,999.0 to 999,999.0)
Bubble: Changes the curvature of the affected vertices. A value of 1.0 produces a half-dome. As you reduce this value, the sides of the dome slope more steeply. Negative values lower the base of the curve below the base of the arrow gizmo. (Spinner value range: float, –999,999.0 to 999,999.0)