Houdini 19.0 Nodes Geometry nodes Group Expand

Group Expand geometry node

Expands or shrinks groups of Edges, Points, Primitives, or Vertices.

On this page
Since 18.0

Expands or shrinks groups of elements.

Inputs

Source geometry

The geometry on which to expand the groups.

Parameters

Group Name

The new name of the created group. If left blank, no groups will be created or altered.

Base Group

The Group to expand.

Group Type

The type of group to operate on. If left as Guess from Group, will attempt to find a group of any type with the given Base Group name or pattern.

Require Primitives Share Edge

When selected, primitives will be expanded to, or shrunk away from, only if they share an edge with the boundary of the group.

Flood Fill to Connected Geometry

When selected, will allow unbounded growth to connected geometry, otherwise when not selected will allow specifying the number of Steps to expand or shrink.

Steps

Specifies the number of steps to expand or shrink. When Steps is positive it specifies the number of iterations to expand. When Steps is negative it specifies the number of iterations to shrink.

Step Attribute

An integer attribute that is set to the first step that any given element is expanded to, or shrunk away from.

Constraints

These options restrict what the group can expand to.

Normal Constraints

Restrict By Normal Spread Angle

Allows restricting growth by the curvature of the geometry. If selected, when expanding a group, it will compare the normals of adjacent components, and will only expand to components that have a normal within the specified angle.

Normal Attribute

If selected, one can specify a vector attribute to use instead of the default normal attribute. The normal attribute must be a 3 dimensional vector on either Points, Vertices, or Primitives.

Connectivity Constraints

Connectivity Attribute

This option allows using one or more attributes that specify connectivity in the geometry. When a Connectivity Attribute is given, groups will be contained within connected regions while growing, and will shrink away from boundaries in connected regions when shrinking.

The Connectivity Attribute can be on either Primitives, Points, or Vertices. When the Connectivity Attribute is on either Primitives or Points, edges that have differing attributes across the edge will be treated as a boundary, and will not be crossed when growing. When the Connectivity Attribute is on Points, groups of points, vertices, or edges, will not grow across edges that have differing attributes at the two ends, and groups of primitives will only grow to primitives that have the same attribute at each point.

Collision Group

Allows specifying a group that will prevent growth while expanding. If specified, expansion will stop at the boundaries of the specified Collision Group. When Shrinking, the group will shrink away from the boundaries of the specified Collision Group.

Collision Group Type

The type of elements in the specified Collision Group. The Collision Group Type does not need to match the Group Type.

Contain Growth within Collision Group

Allows constraining the growth to the interior of the Collision Group, rather than treating the Collision Group as a growth barrier.

Allow Growth to Collision Group Boundary

Allows the growth to include the boundary of the _Collision Group__ while expanding, but prevents it from expanding any further.

Examples

GroupExpandBasic Example for Group Expand geometry node

This example shows how to use group expand to expand a group of primitives while restricting growth by normal spread angle.

See also

Group Expand