Selection Types

The following selection types are available in the Mesh Operations list.

Modifying Selections

You can use procedural selection modifiers to change your selection, similarly to traditional selection modifiers. They are selection operations that take the previous selection and modify it. You can convert polygon to boundary selection, grow, shrink, or invert your selection.

Note:  For more information on traditional selection modifiers, see Using Selection Modifiers.

Boundary Edges

This selection modifier converts a polygonal selection into an edge selection by using the boundary of the polygon selection to determine the edges to select.

You can add this selection operation above the selection you want to modify in the Mesh Operations list:

1.   Add a mesh operation that has a selection input, then add a selection operation to it, as described in Procedural Selection.

The image below shows Edge Extrude applied to a plane using a Select By Falloff selection operation with a Radial Falloff.

2.   Add a Boundary Edges selection operation to the list, then drag it above the selection you want to modify in the Mesh Operations list:

This selects all the edges that were the boundary of the previous selection:

Growing and Shrinking Selections

You can increase or decrease your selection using the Grow/Shrink selection operation.

1.   In the Mesh Operations list, add the selection above the selection operation you want to modify.
2.   In the Grow/Shrink operation's Properties panel, increase or decrease the Steps value to grow or shrink your selection, respectively.

Inverting a Selection

Modo allows you to invert a single selection operation, or all selection operations in the list.

To reverse a single selection operation, in the selection operation's Properties panel, enable the Invert checkbox.

To reverse a list of operations, use the Invert selection modifier. Place it above the selections you want to invert in the Mesh Operations list.

Using Multiple Selection Operations

You can add multiple selection operations to a mesh operation and specify how Modo should evaluate them. When you add a selection operation to the Mesh Operations list, its properties are displayed in the Properties panel under the list.

Blend Mode allows you to specify how Modo treats the preceding selections.

Adding a Select by Falloff (using a Linear Falloff) and a Select by Border selection operation produces the following results:

Blend Modes


The default behavior. The current selection overrides all selection operations below it in the list. Previous selections are discarded, and the new selection is used instead.


Adds the new selection to the previous selection. Elements are treated as de-selected if they are de-selected by all selection operations in the list.


Removes any elements that are selected by the selection operation from the previous selection.


Only selects elements from the new selection operation that are also selected by the first, filtering the previous selection.