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The Houdini Engine for Unity plugin supports Copernicus Houdini digital assets (HDAs). COP HDAs allow you to generate, process, preview, and bake texture outputs from Houdini for use in Unity. The workflow for exporting COP HDAs is similar to the SOP-based workflow for importing assets. COPs workflows allow you to generate, cook, and bake textures to reduce VRAM use in Unity.
COP HDA inputs, outputs, and parameters ¶
The COP node’s inputs are available on the HDA in Unity. The HDA’s exposed path parameters are available as parameter inputs. This is similar to the inputs and parameters on other types of HDAs.
You can add and edit your inputs, parameters, and outputs in the type properties.
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your COP HDA and select Type Properties to open the Operator Type Properties window.
Outputs ¶
When you generate a material, the plugin matches each generated texture to a texture parameter in the material using the texture’s COP output name. For example, to override the material’s normal texture parameter, set the corresponding COP HDA output name to normal.
The plugin supports the following output names:
Output Name |
Description |
|---|---|
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Color texture for the material’s Diffuse or main texture. |
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Normal texture for the material. |
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Specular texture for the material. |
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Roughness texture for the material. |
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Emissive texture for the material. |
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Opacity texture for the material. |
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Ambient occlusion texture for the material. |
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Metallic texture for the material. |
Any texture with a different name is treated as the diffuse or main texture.
Main COPs workflows ¶
Copernicus with Unity has two main workflows:
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SOP HDA with material preview - Allows you to export geometry along with the textures. Houdini Engine automatically converts your COP textures into a Unity material and assigns the textures appropriately.
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COP HDA with texture outputs - Allows you to export generated texture assets without geometry using output attributes. These textures appear as preview quads in the scene and can be baked to texture assets.
SOP HDA with material preview ¶
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In the Geometry network, create a COP Network SOP node.
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Dive into the COP Network node and create a Preview Material COP node
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Assign your generated textures to the Preview Material COP node.
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Step out to the Geometry network, create an Output SOP node.
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Connect the output of COP Network SOP node to the input of the Output SOP node.
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Your geometry needs to be connected somewhere in the network to export along with the textures.
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An alternative is to dive into your COP Network SOP node, then create a SOP Import COP node and connnect the geometry wire to the geo input of the Preview Material COP node.
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Create a Houdini digital asset from the SOP network to export your HDA.
After you load the SOP HDA into Unity, a new folder appears in HoudiniEngineAssetCache/Working/YourAssetName. This folder contains the generated material and textures, which are automatically assigned to the geometry. You can bake these textures and materials like any other HDA output type.
COP HDA with texture outputs ¶
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Create a COP Network node.
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Dive into the COP Network node and create a Subnetwork COP node.
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In the Subnetwork COP node, create your texture network.
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Wire the textures you want to expose to the Output COP node. See Outputs for the type of textures you can expose.
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This example exposes the diffuse, height, roughness, normal, ao, and metallic textures.
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Back out to the Subnetwork COP node.
the node and select Create Digital Asset.-
The Edit Operator Type Properties window opens.
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In this window, select the output that matches your textures from the New Output dropdown menu. See the attributes table in the Outputs section for the correct output names and types.
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Save the HDA.
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Follow the Import HDA into Unreal workflow to import your COP HDA.
Once your COP HDA is in Unity:
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Load the HDA in the scene.
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Each texture output of the HDA appears as an individual quad.
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The material on the first (main) quad uses all textures with supported output names.
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You can then bake the textures like regular HDA mesh outputs.