Houdini 19.5 Character

Character Rig Tree View

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The rig tree view gives a hierarchical view of character components and is compatible with Object-node-based rigs and SOP rigs. Traversals are different between Object rigs and SOP rigs.

Object Node Rigs

Object Node Rigs are composed of Object nodes. When you display Object node rigs, each item corresponds to an Object node in the rig.

The hierarchy in the rig tree is built from the parent-child relationship between these Object nodes. An example is you have two Object nodes named Geo1 and Geo2 and the output of Geo1 goes into the input of Geo2. The rig tree displays a simple hierarchy where Geo1 is the parent of Geo2.

SOP Rigs

SOP Rigs are produced by the output of SOP nodes in the form of points and prims connecting the points. When you display SOP rigs, each item in the tree view represents a point.

When you select a SOP node, it reads the geometry and generates the hierarchy from the points and what prims connect the points.


Rig Tree Hierarchy View

The rig tree provides two options for viewing the hierarchy:

  • Topology: default option that shows the hierarchy as a tree view, showing the parent-child relationship of the Object nodes.

  • Flat View: shows all items in a flat list, disregarding any parent-child relationship.

Example: Showing how to change the Rig Tree Hierchary View

Rig Tree Filtering

The rig tree provides a filtering option to show only your desired items in the view. You should add the name into the filter system to display what you want. Wildcards are also accepted.

In Topology view, if you filter an item with at least one child, it also shows the parent.

Example: Topology view showing at least one child and its parent

Flat List view only shows filtered items.

Example: Flat view showing only filtered items

Rig Tree Flat List Sorting

In Flat List view, the rig tree provides a sorting option to determine the order to display the items in the view.

Example: Showing the Flat List Sorting options


The gear menu in the right corner of the pane provides a set of useful options:

  • Reset: causes the pane to retraverse the Object nodes or points of a SOP node

  • Parameter Editor - Select Geometry

    • Show Window when Selecting: automatically opens a rig tree pane if it’s closed when interacting with a parameter selector; this can help with selections if the rig tree is closed

    • Close Window after Selection: after the parameter selection is done, if you opened a pane on selection start it will now close

  • Node States

    • Show Window when Entering: automatically open up a rig tree pane if it’s closed when you enter a node state; this can provide access to rig tree custom features while in the node state if the rig tree is closed

    • Close Window after Exiting: if you open a pane on state enter it now closes

Example: Showing the options menu and its settings

Custom Behavior

Rig Tree Selection

Rig tree selection has the following behavior:

  • With Object node rigs, selecting an item in the rig tree view selects that Object node in the network view.

  • With SOP rigs, selecting an item in the rig tree view automatically enters the node’s state, or the default Rig tree select state, and selects that point.

    The rig tree shows the icon of the state that it enters on selection.

Example: Showing an Object node rig tree view
Example: Showing a SOP node rig tree view

Rig Tree Drag and Drop

Rig tree drag and drop has the following behavior:

  • For Object node rigs, drag and drop rearranges the connections between the Object nodes.

  • For SOP rigs, drag and drop performs a parenting operation if the node state supports it.

    See Parent Joints SOP or Skeleton SOP for examples.

Rig Tree Renaming

Rig tree renaming has the following behavior:

  • For Object rigs, renaming by default changes the name of the associated Object node.

  • For SOP rigs, renaming changes the name of the selected joints if the node state supports it.

    See Skeleton SOP for an example.

Rig Tree Deletion

Rig tree deletion has the following behavior:

  • For Object rigs, it does nothing.

  • For SOP rigs, the delete operation deletes the selected joints from the skeleton if the node state supports it.

    See Skeleton SOP or Skeleton SOP for examples.

Rig Tree Custom State Actions

Custom state actions are functions that users can access via the context menu that’s opened by right-clicking in the rig tree (actions listed at the bottom of the menu).


KineFX characters

Geometry-level procedural rigging and animation with SOP-based rigs.

Object-level characters

Object-level rigging and animation with bone-based rigs.