In Blender there is a 'Mask ID Node' in the 'Compositor' to extract IndexOB or IndexMA of a Multilayer EXR. But how to work with these passes in other compositing packages? In e.g. Nuke or After Effects there is nothing like an ID Node.
To make it work in all other packages you need to manually create custom output channels and append the passes to your Multilayer EXR via Blenders Compositor:
In Nuke you can use J_Ops. With this tool you don't need the additional node setup above. There is a tool called J_GotSomeID which is able to detect such IDs from the EXR Multilayer automatically.
- Select the pass (IndexOB or IndexMA)
- Set the Selection Mode to Find
- To detect the IDs click Autofill