Houdini 20.0 Unreal

PDG Asset Link

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The PDG Asset Link allows you to cook and impor results from PDG Graphs embedded in HDAs directly in Unreal.

Creation

The PDG Asset Link is automatically created after instantiating an HDA that contains a TOP Network.

It displays a list of the TOP Networks available in the HDA and the TOP Nodes available in the currently selected TOP Network. This also displays the options to cook, cancel, dirty all, and unload all work item objects.

Filters

The PDG asset link uses a filter that specifies a prefix for the node names to avoid showing every TOP network node. This controls if they list in the Asset Link UI.

The default value for this filter is HE_, so only these are listed in the PDG Asset Link. For example HE_Terrain or HE_Trees.

The TOP output filter is another prefix filter to identify nodes that produce ouput BGEOs. By default, the filter is set to HE_OUT_, so only these are load these work item output files. For example HE_OUT_Trees, HE_OUT_Roads, or HE_OUT_Buildings.

Those filters can be modified or disabled in the PDG Asset Link UI.

Loading Work Item Results

When you cook the PDG Graph, it imports Work Items geometry output files (bgeos) that have successfully cooked on the TOP Output Nodes. The results are loaded on actors that reproduce the PDG Graph’s hierarchy:

  • TOP NETWORK

    • TOP NODE

      • WorkItemOutput1

      • WorkItemOutput2

      • WorkItemOutput3

Cooked PDG results are considered temporary like normal HDA outputs. Until baked, it’s owned by the Houdini Asset Actor. This means if you dirty or change the PDG assset, it can potentialy destroy or update them.

The PDG Asset Link has its own bake section, which allows for fine grain controls to decide how the PDG graph’s results are baked.

You can choose to bake all outputs, only the selected top network, or selected TOP node.

You can decide if you want to replace existing assets and actors created from a previous bake or create new ones.

Asynchronous Importer

The PDG Asset Link allows you to use an asynchronous importer commandlet to import Work Item outputs once they are ready. This reduce lock ups of Unreal and is useful when processing lots of large meshes.

Asynchronous import can be enabled/started/stopped in the Work Item Import Settings entry in the Houdini Engine menu. The PDG Asset Link displays the status of the async importer in its details UI when in use.

Once started, the commandlet automatically imports the BGEO files from output work items, creating their UAssets. After a successful import, the commandlet notifies the PDG asset link which then initiates the Uasset in the level.

Unreal

Getting started

Basics

Using Houdini Engine

Reference

Houdini Engine for Unreal Engine is a plug-in that allows integration of Houdini technology into Unreal. Session Sync and Node Sync are two features of the Houdini Engine Plugin to interact with a live session of Houdini.

This plug-in brings Houdini’s powerful and flexible procedural workflow into Unreal Engine through Houdini Digital Assets. Artists can interactively adjust asset parameters inside the editor and use Unreal assets as inputs. Houdini’s procedural engine will then “cook” the asset and the results will be available in the editor without the need for baking.

General information:

Compatibility:

Currently, the plugins has binaries that have been built for UE5.3, 5.2, 5.1, 5.0, UE4.27 and UE4.26, and is linked with the latest production build of Houdini.

Source code for the plugin is available on this repository for UE5.3, 5.2, 5.1, 5.0, UE4.27, UE4.26.

Note

UE5.1 and UE5.0 use the same source files/branches, the 5.0 sources are also intended to be used with 5.1.

Support and reporting bugs:

SessionSync

The Houdini Engine SessionSync feature allows you to connect to a session of Houdini Engine running inside Houdini with its GUI. It supports all the features of the regular Houdini Engine workflow and additional features specific to Session Sync.

Houdini Engine uses a non-UI version of Houdini while Session Sync lets you see and interact with the Houdini session through Houdini’s user interface. It also synchronizes changes made in either Unreal or Houdini so both programs can make changes and see the same results.

NodeSync

NodeSync is a feature for the Houdini Unreal Engine Plugin that enables sharing assets between Unreal and Houdini Session Sync. It works for Skeletal and static meshes.

You can send and receive data to and from Unreal without a dedicated HDA. It works with Static and Skeletal meshes as well as Actors.

Houdini Niagara

The Houdini-Niagara plugin allows you to exchange point cloud data between Houdini and Unreal’s Niagara system using the HoudiniNiagara Data Interface. You can export Houdini’s attribute data as HoudiniPointCache assets. These can then be imported into Unreal to use the Niagara systems and emitters to create complex effects and particle systems.

The Houdini KineFX Live Link plugin lets you control rigs in Unreal directly from KineFX in Houdini.