Chair grouped. Within the group of two objects: chair itself and the auxiliary "null_for_patina", which is used in conjunction with VRayDistanceTex texture to simulate wood patina in the material of the chair. Copy the chair, if necessary, should be a group, while in VRayDistanceTex in the list of objects you need to make the newly created (by copying the chair) null_for_patina01 etc. in the case of repeated copying.