The basic procedure is as follows:

Activate a cryptomatte AOV. This should be configured to write to an RGB EXR file.

Create a cryptomatte shader and connect it to an AOV Output.

Connect a cryptomatte shader to AOV shaders in the Arnold ROP (Properties > Output tab).

Render the EXR to disk. You'll get the AOV expanded into all the cryptomatte data, with metadata. Options on the cryptomatte shader can be considered global options for the system, in a sense an extension of the Arnold options.

cryptomatte workflow example can be found here. More information about cryptomatte AOVs can be found here.

Cryptomatte Globals

Sidecar Manifests

Cryptomatte Depth

Strip Object Namespaces

Strip Material Namespaces

Standard Cryptomatte

User Defined Cryptomatte

User Cryptomatte AOV 0

AOV Name 0

Source User Data 0

User Cryptomatte AOV 1

AOV Name 1

Source User Data 1

User Cryptomatte AOV 2

AOV Name 2

Source User Data 2

User Cryptomatte AOV 3

AOV Name 3

Source User Data 3


Preview in Exr

Process Maya

Process Paths

Process Obj Path Pipes

Process Mat Path Pipes

Process Legacy