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 installer, run it and be sure to check the Unity plug-in during installation. The next time you run Unity, select Open Project, click on Open Other then navigate to c:\Users\Public\Documents\Unity Projects\ and choose the Houdini_Engine_Project.
- Launch the Houdini installer.
- Follow the steps and make sure to select the "Houdini Engine for Unity" option on the Houdini Engine installer screen.
- In Unity you can either load the default Houdini Engine project or open a Unity project you wish to use Houdini Engine on.
- In Unity, go to Assets > Import Package > Custom Package...
- Navigate to C:\Users\Public\Public Documents\Unity Projects\Houdini_Engine_Project_X.Y.Z where X.Y.Z is the version of Houdini you just installed.
- Select the houdini-engine.scripts.unitypackage file for import and import everything inside.
- You will see the Houdini Engine menu but it is not fully functional yet. Restart Unity to initiate the engine properly.
3. Load an Asset into Unity
There are sample assets the come with the default Houdini project. If you want to use them you'll need to copy the Assets/OTLs and Assets/Resources folders into your own Assets/... Unity project directory.
You can also open the default Unity project from C:\Users\Public\Public Documents\Unity Projects\Houdini_Engine_Project_X.Y.Z. Doing so will automatically include the Houdini Engine plugin as well as the sample Houdini assets.
To use one of the sample assets, click on OTLs > Samples. You can click and drag them into your Hierarchy to load then into Unity. Here are a couple of these assets being used in Unity:
Curve Decorator Asset
This video introduces you to the Curve Decorator Asset which makes it easy to propagate props into the Unity editor using an input curve. This asset uses the Houdini Engine to instance the objects and includes a number of procedural controls for tweaking the results.
Mesh Decorator Asset
This video introduces you to the Mesh Decorator Asset which makes it easy to propagate props into the Unity editor using an input surface. This asset uses the Houdini Engine to instance the objects and includes a number of procedural controls for tweaking the results.
4. Create your Own Asset
You can use Houdini Engine for Unity to work with existing assets or you can create your own. Below are a couple of lessons outlining the steps needed to create digital assets in Houdini.
This lesson outlines the basic steps for getting a procedural asset from Houdini to Unity. This is not a proper game asset but simply an example of the workflow for learning purposes.
This lesson creates a procedural barrel for use in Unity as a proper game asset. You will learn how to use Houdini's node-based workflow to build up controls for the asset.
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.