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Overview
In Houdini you build scenes using networks of nodes. For example, 
Object nodes represent characters, props, simulations, or transforms in the scene, while 
Geometry nodes create or modify geometry.
You can turn your own networks into reusable custom nodes with their own user interfaces. A custom node is called a digital asset. It lets you package a complex action, a character, or a set of tools, into something that users can install and use just like any other part of Houdini.
For example, you could create a light object asset that contains your custom light and shadow shaders, has defaults tweaked they way you want them, and only exposes the controls you want lighters to use.
Digital assets contain the node network that defines how they work. They can also contain extra files, which the contained nodes can reference. For example, a character asset can contain all the textures the character needs, so you don’t have to worry about making them available to users separately.
You can create a user interface for your asset by promoting parameters on the contained nodes up onto the asset node. You can combine this with scripting to create very powerful user interfaces.
Houdini can get assets from a central network location, allowing you to update the assets used by artists instantly and simply.
Common uses for digital assets
Characters
You can put all the parts your character needs (bones, skin geometry, textures, materials) inside a single node with a custom user interface for the character controls you want animators to use. The animators can interact with the character node exclusively without being exposed to the implementation details.
A digital asset makes it easy to do things like rig with a low-poly skin and switch to a high-resolution skin for rendering. Just create a switch between the two skins in the geometry network, and promote the switch’s control up to the asset as a custom parameter.
Procedural props
You can, for example, package a entire workflow for making buildings as a digital asset. It might have controls for architectural style, number of floors, placement of windows, randomized elements, and so on. Then you can then put down multiple instances of the node to create different buildings in a city.
Procedural effects
Similarly, you can package up a complex effect such as an explosion, give it an explosion-specific user interface, and give it to artists to reuse without having to understand what’s inside.
Custom nodes
You can package up large, complex node networks into a single, reusable node with a custom interface for use in other networks. For example, you could create a geometry node (SOP) that randomly jitters points in a model. Installing the asset library makes the custom node available alongside all of Houdini’s other nodes (many of which are actually assets themselves).
Sets and lighting rigs
You can create reusable sets and lighting rigs that allow artists to create complex setups with a single node.
Materials
Material assets let you include support files, such as textures, with the material, so you don’t have to worry about external files.
Rendering
You can create rendering assets that contain sub-renderers to generate layers, and compositing networks to post-process rendered images.
How digital assets work
You create a digital asset by converting a subnetwork. See creating a digital asset for more information.
Digital assets are stored in a digital asset library file, with a .hda (Houdini Digital Assets) extension. (Older versions of Houdini created libraries with a .otl extension.) A library file contain one or more digital assets.
Houdini loads any asset libraries it finds in HOUDINIPATH/hda. You can also manually install libraries from other locations using the operator type manager.
Orbolt
The Orbolt store contains many free and for-pay digital assets you can download directly into Houdini and use in your scenes.