V-Ray Object Settings
This property contains VRay-specific options that apply to the selected object(s). You can apply the VRayObjectProperty by selecting the object(s) and choosing Get>Property> VRay Object from the Render menu
At this time, the object property is used only to control the object ID.
Object Id - this is an ID for the object. This is used by the MultiMatte render element which allows you to create selection masks based on Object IDs. ID values have no special meaning and can be chosen arbitrarily.