Cryptomatte in the Arnold User Guide for the full shader documentation.
Arnold supports cryptomatte,�an ID matte creation tool created by�Jonah Friedman. It creates ID mattes automatically with support for motion blur, transparency, and depth of field.
Cryptomatte shader available in Shop> Arnold Vopnet
Create an OUT_AOV node and connect your Cryptomatte node to it.
Connect a cryptomatte shader to AOV shaders in the Arnold ROP (Properties > Output tab).
Render the Cryptomatte AOVs to disk (as EXR).
Opening the EXR in a compositing package such as Nuke or Fusion shows the available cryptomatte AOVs.
Note:
There is a limitation with the current cryptomatte implementation, where object names are expected to follow the MtoA naming convention. A workaround is to manually set the " crypto_asset " string attribute on the geometry you want to belong to the same asset ID, that works.
