To achieve this, follow these steps in Blender using the Cycles Render Engine (Version 3.5):
- Set your render engine to Cycles.
- In the View Layer Properties, locate the Cryptomatte section.
- Choose the Cryptomatte option that suits your needs: Object, Material, or Asset.
- In the Compositing tab, enable the Use Nodes option.
- You'll find a Render Layers node and a File Output node. Press Shift+A to create a new output node.
- Connect the File Output node to your Crypto Passes.
- Adjust the node options by changing the file output format from PNG to OpenEXR MultiLayer.
- Within the node view of the File Output node, click on Add Input.
- Add your three Cryptomatte passes and make sure their names match those in your Render Layers.
- Render your images, and you're all set for compositing.