This page provides details on the Object ID extra attribute used in V-Ray.
Overview
The ObjectID channel represents integer values that correspond to the specified object IDs to objects in your scene.
UI Path: ||Select mesh|| > Attribute Editor > Attributes menu > VRay > Object ID
Parameters
This group allows to assign an object ID to parts of the scene, for use with the Multimatte Render Element.
Object ID – Specifies an ID for the objects below the transform.
