- User Data (named userid) is applied to each object that is required a user AOV. You can define any custom name for the objects in the userid parameter, they are used as the IDs in the custom user AOV.
- Create a Custom AOV called crypto_userid.
- Create a cryptomatte shader and under AOV name, enter crypto_userid.
- Set userid as the Source User Data in the shader.
- Render the scene. You should be able to view the crypto_userid AOV.