Houdini 18.5 Digital assets

Creating a digital asset

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You can create a digital asset of any type (Object, Geometry node, Dynamics node) by converting a subnetwork of that type into a digital asset.

See how to install and use assets for how users can access the new asset after it is created.

How to create a digital asset

  1. Create a subnetwork containing the nodes that will define the behavior of the asset.

    • Make sure you use relative references in expressions so they will still be valid inside the asset. For example, use ch('../copy1') instead of ch('/obj/geo1/subnet1/copy1').

    • To quickly put a bunch of nodes inside a subnetwork, select them, right click and choose Actions ▸ Collapse into Subnet.

  2. Right click the subnet node and choose Create digital asset.

    (Houdini will warn you if you have references inside the subnet to nodes outside it, since they won’t work in the digital asset.)

  3. A dialog appears that lets you name the asset and decide where to save it.

    • The Operator label is the human-readable name that shows up in Houdini’s user interface, for example Three Light Rig.

    • The Operator name is a unique internal name to distinguish it from other nodes, for example threelightrig.

      You can change the label later, but you can’t change the name without recreating the asset. In a studio environment, you may want to ensure your node names don’t collide with Houdini’s node names, or vendor node names, by using namespaces.

    • The Save to library path sets the name of a library file to save the asset definition into. See asset libraries below for more information.

  4. Click Accept.

    Houdini opens the Type properties window for the new node type to let you edit its options. (To open the type properties window again later, you can right click an instance of the asset and choose Type properties.)

    You can use this window to set up the new node type’s parameter interface.

    You can write documentation on the asset’s Help tab to explain its purpose and controls to users, using a Wiki markup language.

Serving assets and data over HTTP

Most places you can specify a file in Houdini will also accept a URL. You can use a web server to serve shared .hda asset libraries as well as shared project data (such as textures).

Specifying files inside an asset using opdef:

You can embed files inside the digital asset, using the Extra files tab in the Type properties window.

In parameters where you can specify a file path, you can use the following syntax to instead specify the content of a section inside an asset:


You can use this to include all the files an asset needs (such as textures) in the asset itself.

For example:


You can also use opdef:.?section (to get a file from the current asset) and opdef:..?section (to get a file from the parent of the current node). For example, if you have a File node directly inside an asset, you can load a geometry file from the asset using:


Note that relative opdef: may not work in all places. For example, in a shader you can say texture("opdef:/Shop/foo/texture.rat") but you can’t use opdef:.. because the compiled VEX has no concept of a parent node.


You can interactively choose embedded files from inside assets using the Houdini file chooser. Click the opdef: root on the left side of the chooser window.

Asset libraries

Digital assets are stored in digital asset library files, with a .hda extension. (Older versions of Houdini used a .otl extension.) Houdini loads any .hda (or .otl) files it finds in HOUDINIPATH/otls.

The default library save location when you create a new asset is in your user account’s Houdini preferences directory (under HOUDINIPREFS/hda), so the asset will only be available to you. In a studio environment, you might save the asset in a central, network-accessible directory (that has been added to the Houdini path) so other users can install it.

A library file can contain multiple assets (this means you can keep saving new assets into the library for your account). However, we recommend you store each asset in a separate library file. This makes it straightforward to share some assets and not others, and keep track of which assets are in which files.

Embedding assets in the current scene file

  • You can embed an asset in the current .hip file instead of in an external file. This may be useful for testing or sharing example files. When you create an asset, set the Save to library field to Embedded.

  • You can enable an option to save the definitions of any assets used in a scene file with the scene file. This allows you to use the scene file even in environments where the asset libraries are not available, but can cause confusion about which definitions are being used. Choose Windows ▸ Operator type manager, click the Configuration tab, and turn on Save node definitions to HIP file.

  • When an asset is both embedded in the scene file and available from a library file, by default Houdini will load the asset from the library. To reverse this, choose Windows ▸ Operator type manager, click the Configuration tab, and turn on Prefer definitions saved with HIP file.

  • Although Houdini lets you embed an asset definition in the scene file, we recommend you store all assets in library files.

    One issue is that Houdini only embeds definitions for assets that are used in the scene. If you unknowingly delete the last instance of an asset and save, the definition of the asset will be lost.

Digital assets

Getting started

Creating assets

Next steps