In Houdini, networks of nodes can be easily wrapped up into Houdini Digital Assets then shared with other artists. With the Houdini Engine, these assets can be loaded into the Unity game editor with procedural controls available to artists.
The results can then be further manipulated in Unity. Anytime a parameter is changed on the asset, the Houdini Engine is called upon to "cook" the network of nodes and publish the results to Unity. This allows for deep integration of Houdini Digital Assets into a Unity game development pipeline. The game content is baked out when the game is published.
To get started with Houdini Engine for Unity, follow the steps outlined below. Houdini, Houdini FX, Houdini Indie, Houdini Engine or Houdini Engine Indie licenses can be used to load assets into Unity. If you don't have a license then a 30-day Trial is available.
1. Download the Houdini Engine
To access the Houdini Engine, download the Houdini installer which comes with the Unity plug-in. While the plug-in connects Unity to the Houdini Engine, a full Houdini install is needed to cook the results under the surface. You can run the Engine using either a Houdini, Houdini FX, Houdini Engine license. Houdini Indie and Houdini Engine Indie will work with limited commercial asset files. Houdini Engine for Unity works with Unity 4.6 or higher.
2. Install and Load the Plug-in
Once you have downloaded the Houdini installer, run it and be sure to select the "Houdini Engine for Unity" option on the Houdini Engine installer screen.
After installation, you’ll need to import the plug-in package into your Unity project. You can find the plug-in package at <Houdini installation>/engine/unity/HoudiniEngineUnity_v2_beta.unitypackage. If you don’t see it, re-run the installer and make sure to enable the Houdini Engine for Unity option. This is the new Version 2 plug-in that has lots of new modern features that makes it more compatible with Unity.
To import the plug-in into your Unity project:
- Make sure to delete any previous Houdini Engine for Unity plug-in folder. You’ll find it in Assets/Plugins/HoudiniEngineUnity. If you have the HoudiniEngineUnity folder, delete it along with all its contents from inside Unity.
- In Unity, go to Assets > Import Package > Custom Package
- Navigate to and select the <Houdini installation>/engine/unity/HoudiniEngineUnity_v2_beta.unitypackage
- Make sure all files are selected (they should be by default), and select Import.
- Unity will now install the plug-in files into Assets/Plugins/HoudiniEngineUnity
- Once complete, you should see the Houdini Engine Unity menu show up at the top if you move the mouse over to the menu in Unity.
3. Load an Asset into Unity
Currently the EverGreen asset is shipped with the Houdini Engine for Unity plug-in. You’ll find the asset file under Assets/Plugins/HoudiniEngineUnity/HDAs/Evergreen.hda in your Unity project.
You can drag & drop the EverGreen asset into your Scene or Hierarchy window to instantiate it. When you do that, a Houdini session is launched in the background, and the asset will be loaded into it, then cooked. In Unity, it will be created as a Houdini Digital Asset gameobject hierarchy which consists of several gameobjects with Houdini Engine scripts, a custom Inspector UI, generated meshes, colliders, and materials.
To load other assets, you can place the asset’s .hda or .otl file in your Unity project’s Assets folder, then drag & drop into the Unity scene or hierarchy window.
Another option is to load the asset from the menu: Go to Houdini Engine Unity > Load Houdini Digital Asset then select the asset file.
For more information about the plug-in, please see the online documentation:
4. Creating Digital Assets for Unity
To learn how to use the Unity plug-in, check out the Guard Tower project which teaches new Houdini users how to construct game-ready assets. The main goal is to show the process of building the Guard Tower scene procedurally using Houdini then to deploy those assets inside Unity using the Houdini Engine plug-in.
5. More Learning
The Game Tools Learning Path offers a number of games-focused lessons covering Houdini and the Houdini Engine. These lessons teach you how to create digital assets for use in host applications such as Unity and are a great resource for game makers to learn how to go procedural.