Arnold 5: (AlShaders2): https://github.com/anderslanglands/alShaders2/releases
Nuke and Fusion: https://github.com/Psyop/Cryptomatte
Arnold 5 Cryptomatte
Cryptomatte for Arnold 5 is being released as part of AlShaders, as before, but is now a standalone node. Arnold 5.0.1 adds support for “AOV shaders”, which allow code to run on all materials in a scene, without manually connecting passthrough nodes. This improves the workflow in numerous ways. Using a central AOV shader node gives easy access to global Cryptomatte settings (on the one central Cryptomatte node). It is now also much easier for a studio to create a customized version of Cryptomatte, since the code does not need to be embedded in a surface shader. In addition to adopting the AOV shader methodology, we’ve added other features as well, such as sidecar manifests that work with deferred-loaded stand-ins, and “integer offsets” for modifying names.
Arnold 5 Documentation: Cryptomatte documentation, MtoA, MAXtoA, C4DtoA, HtoA.