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Add a user attribute for MatteID0.

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Set its type and color value.

Add PxrMatteID

Create a Houdini buildarray node to connect to the Utility Pattern on the PxrSurface material. Then connect a PxrMatteID Pattern node to the buildarray as shown below.

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In your PxrMaterialBuilder Network, add a PxrMatteID VOP.  Set the color as the user attribute above.

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Connect PxrMatteID's resultAOV to PxrSurface's Utility Pattern.

Set up AOV for Output

Choose the correct/corresponding MatteID AOV output from the RenderMan ROP node Displays Tab

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