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This window lets you manage operator type libraries and set options for how Houdini handles assets and operator type libraries.

Colors of definition names

If an operator definition name is written in black, the current definition is being used for that operator type. Names in yellow are also being used as the current definition for that operator type, but there is a more recent definition available in another operator type library. Names in red are not the current definition for the specified operator.


Changing your color scheme will change these colors.

To make a definition current for an operator type, click RMB on the operator and choose Use This Definition. This setting overrides the global preferences on the Configuration tab, and are stored in a hip file. An operator type definition that has been given these overrides are green. To removed the override, click RMB on the operator and choose Clear Definition Preference.

The text box below the tree view lets you to search for operator types by name. You can find the current definition, latest (last modified) definition, or next definition in order. You can use wildcards in the name.

For example, to find the current definition of an operator named MassiveBrainExplosion, type *Brain* and click Current Definition.

HDA file context menu

This menu appears when you press RMB on the name of an operator type library file.


Unloads the type library and removes it from the library search path (that is, the OPLibraries file). This does not delete the actual .hda file, it just makes Houdini unaware of it.


Reloads all the HDA file context menu.

Merge with Library

Merges the contents of this library with one you choose.

Expand/Expand All

Shows the contents of the HDA file.

Sort Ascending/Descending/None

Choose how to sort the files in the menu.

Operator context menu

This menu appears when you press RMB on the name of an operator.

Type Properties

Opens a window for editing the custom operator’s settings. This item is only available for the current definition of an operator (for example, if you have two versions of “my_operator” available, only the active definition will have this item in its context menu).


Copies between .hda files, which keeps the last path.


Makes a duplicate within an .hda, which defaults to the type’s current path.

Jump to Next Definition

If you have multiple definitions of a custom operator (for example, within the .hip file and on disk, or in several directories on disk), this item selects the next definition. This is useful for quickly finding all the definitions for a single operator.

Show Namespace Order

If there are other operators of the same base name but in a different namespace or with a different version, then this item displays a list of such operators sorted according to the precedence order. It is useful to determine the operator type resolution order that Houdini uses when an unqualified (base) name is used in scripts. Houdini will use the first operator in that list that best matches the unqualified name.

Update Time Stamp

Sets the custom operator’s “last modified” time to now. This is useful if you have Houdini configured to use the last modified operator version and you want to rearrange the order.

Use This Definition

Defines which operator to use, since definitions may be located in multiple libraries.

Clear Definition Preference

Clears the selected operator to use. This option is only visible if after you choose Use This Definition for an operator.


Removes the custom operator from the HDA file. You cannot delete an operator type if it is in use.

Configuration tab

The options on this tab control how Houdini chooses between multiple versions of the same operator type.

Give Preference to Definitions from Index Files

Operators defined in index files (SHOPsurface, SUBobj) have priority over operators defined in HDA files.

Give Preference to Definitions Saved in Hip File

Definitions embedded in the hip file have priority over definitions stored on disk.

Give Preference to Definitions with Latest Date

Use the operator with the latest “last modified” time. This means the latest date stamp that the asset definition inside the HDA library file has, not the date stamp of the HDA library file on disk.


If you have more than one of the priority options turned on, the options higher in the list have priority over the options lower in the list.

Save Operator Definitions to Hip File

Embeds copies of the HDA definitions used in the current hip file in the hip file. This makes the hip file larger but means the custom operators the hip file depends on are always available.

Save Definitions of Unlocked Assets to Hip File

If this option is turned on, definitions of assets with unlocked instances in the hip file are saved to the hip file, even if Save Definitions to Hip File is turned off.


This option is irrelevant if Save Definitions to Hip File is turned on because that option always saves all definitions to the hip file.

Display Warning for Out of Date Operators

If you load a hip file (or use otrefresh) and an active operator is out of date, but Give Preference to Definitions with Latest Date is not on, Houdini will pop up a warning.

Display Warning for Operators With Incomplete Definitions

Generates a warning if you load a hip file containing a node with an incomplete asset definition because a complete definition is not available.

Create backup files when saving libraries

Saves a backup copy of the old version whenever you modify an operator type library file.

Safeguard Operator Definitions

Removes the Allow Editing of Contents and Match Current Definition menu items from the node tile context menu. Turning this option on can protect users from modifying operator definitions.

Leave Values When Defaults Change

Don’t update the parameter values of existing nodes when you change an operator’s defaults.

Use OPlibraries Files to Find HDAs

This option exists for backward compatibility. If this option is turned on, Houdini scans the HOUDINI_PATH for files called OPlibraries which contain a list of HDA files to load. This is what was done in previous versions. If this option is turned off, Houdini scans HOUDINI_OTLSCAN_PATH for *.hda and loads all matching HDA files.


If only HOUDINI_PATH is defined, then Houdini always uses the most recent .hda in the path, not the order they are defined.

Asset Definition Toolbar

Controls the visibility of the Asset Definition Toolbar that appears at the top of Parameter dialogs. This bar shows the path to the HDA file that defines the node pointed to by the Parameter dialog.

The Asset Definition Toolbar can be hidden completely, or it can be in a read-only mode where it simply displays the HDA path, or it can be in a mode where it presents a menu listing all HDAs that contain a definition for the asset.

Namespace Hierarchy

Displays the value of the HOUDINI_OPNAMESPACE_HIERARCHY used to build the namespace hierarchy and sort the operators with the same base name.