Houdini 20.5 Unreal Meshes

Using procedural modeling assets in Unreal

Workflow to generate a landscape in Houdini and import it into Unreal

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This covers how to expose

A few key things you will learn in this workflow:

Copy over the HDA file

Before you begin, copy the Houdini HDA file that you will be working with throughout this workflow:

  1. Open a file browser window and then navigate to your Houdini Engine install directory.

  2. In the install directory, navigate to the \Plugins\HoudiniEngine\Content\Examples\hda folder.

  3. In the \hda folder, copy the HEUE_Geometry_Fence.hda file.

  4. Navigate to your user directory and then create a new folder named \ProceduralModeling.

  5. In the \ProceduralModeling working folder, paste the HDA file.

  6. Run Houdini.

  7. Open the HEUE_Geometry_Fence.hda workflow file and become familiar with its contents.

Inspect Houdini setup (optional)

The following sections inspects how the content example was created and a few important setups before going into Unreal. You can skip to the Import to Unreal section to see the Unreal setup.

Mesh generation setup

  1. Double-click the geo1 to enter into Geometry view. Then double-click hece_geometry_fence1 to enter the Surface Operator network view.

  2. Double-click the Mesh_Generation subnetwork. You can now see the setup for the procedural modeling fence.

  3. Locate the Output SOP at the end of the node network.

    • This node is important to add to the end of your modeling setup. Houdini Engine for Unreal reads the Output SOP node and exports your entire node network. If you want to export a specific node, select that node and set the display flag on it.

Mesh Prep setup

This example uses packed primitives to export multiple geometries using one HDA. It also shows how to use special attributes to send a bake folder and output name to Unreal.

  1. In the SOP view of hece_geometry_fence1, double-click Mesh_Prep subnetwork.

  2. Select the Attribute Create SOP namned attribcreate_path.

    • The Name parameter is set to unreal_bake_folder which sets the folder path to where your bakes output to in Unreal. This can be useful to organize a large batch of baked assets instead of using the default folder. See Attributes and Groups for more information.

    • The String parameter is set to chs("../../out_path"). The chs represents the channel string and the out_path is a name used later for a promoted parameter. This is explained in the Promote parameters for export section.

  • The Attribute Create SOP named attribcreate_name performs a similar task but using the unreal_output_name attribute which allows you to set the name of the baked asset.

  • The sequence from the Blast SOP to the Merge SOP separates the fence into planks, support_beams, and end_post. You can use packed primitives to separate multiple meshes in your output. See Mesh generation for more information.

Promote parameters for export

  1. the hece_geometry_fence1 and select Type Properties. Locate the Parameters tab.

  2. On the Existing Parameters section, you can see all the promoted parameters that will carry forward into Unreal.

    • In the Design folder, these promoted modeling parameters allows you to change them in real-time in Unreal before baking it out into an asset.

    • In the Output folder, these promoted naming parameters allows you to rename the different meshes and set the baked folder on the HDA before baking it into an asset.

Create HDA for Unreal

  1. Step out into Geometry view, the hece_geometry_fence1 subnetwork and select Create Digital Asset.

  2. In the pop-up window, change the Asset Label name to hece_geometry_fence.

    • You can change the other settings to your preference.

  3. Select Acccept.

Import into Unreal

Make sure you have a Houdini Engine for Unreal session running. See Session for more information.

  1. In Unreal, import the fence_examplev01 HDA.

  2. the HDA and select Instantiate at the origin.

    • You should now see the fence in the viewport.

Change Houdini parameters

During the Houdini setup, certain parameters were promoted to use them in Unreal.

  1. In Houdini Parameters detail panel, locate the Mesh tab.

    • You can see the exported parameters from Houdini that you are able to change in Unreal now.

  2. Change the parameters and see the fence change in real-time in the viewport.

  3. In the Output section, you can see geoemetry exports, renaming, and vizualization parameters.

    • The Output Folder allows you to set the output path for the baked assets.

    • The export checkboxes allows you to bake out separate geometries for the full fence, panel, and fence post. If you check multiple ones, they will bake out as separate Unreal Static Mesh Actors. You can also set the name of the baked out assets.

    • The Visualize Name Attributes dropdown allows you to visualize the mesh name or output folder as text in the viewport.

Bake into actor

Once you're done with the fence parameters, you can bake the HDA to change it into an Unreal Static Mesh Actor.

  1. In the outliner, select the fence_examplev01 HDA.

  2. In the Houdini Engine panel, select Bake.

    • In the outliner, you should see a folder fence_examplev01 with the Static Mesh Actors you checked to export. They are also named to the label you put in the output fields.

See also

Meshes