Houdini Engine for Unity
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This section provides useful tips to troubleshoot issues.

When using the Unity plug-in, a hidden Houdini scene is being managed by Houdini Engine:

  • When an Houdini Asset is instantiated in Unity, Houdini Engine instantiates the same asset inside the Houdini scene.
  • Asset Overview values in Unity are mirrored in the Houdini scene.
  • When input geometry is connected to a Houdini asset in Unity, this geometry data is marshalled and replicated into the Houdini scene.
  • Curves are also replicated in and linked to the Houdini scene.
  • Lastly, the geometries that the Houdini asset Outputs_Overview in the Houdini scene are replicated back into Unity.

Therefore the internal Houdini scene is at the very core of how Houdini Engine works. This internal Houdini scene is normally hidden away from the user.

However, it is useful to access this internal scene for investigating problems and unexpected behavior. For example, this is particularly useful in cases where the asset is behaving correctly in standalone Houdini, but not in Unity.

Debugging Workflows

In Unity, there are options in the HoudiniEngine menu to open or save the internal Houdini scene. This allows the internal Houdini scene to be inspected in a separate Houdini UI session. This is extremely useful when troubleshooting Houdini Engine issues. In order to open the scene, a Houdini license capable of running the Houdini UI is required.


For Inputs geometry, inspecting the scene in Houdini will allow to see exactly what data and metadata has been passed in from Unity.

This could also be useful for authoring assets while viewing this internal Houdini scene. The scene can be saved in Unity, and then loaded into Houdini. The author can then make changes to the asset in the Houdini UI, save it, and then Rebuild the asset inside Unity to immediately see the changes.

Houdini Engine Debugger

Another method to troubleshoot issues would be to use a Houdini Engine Debugger session. This creates a running interactive instance of the Houdini application which is used as the actual internal Houdini scene. This allows fast iteration when debugging a digital asset as it allows to see changes in the Houdini scene in real-time. For more information, see Houdini Engine Debugger.