setBackgroundMesh( mesh ) {

		if( this._backgroundMesh ) {

			this.remove( this._backgroundMesh );
			this.unbindBackgroundMeshProperties();

		}

		this._backgroundMesh = mesh;

		if ( this._backgroundMesh ) {

			this.bindBackgroundMeshProperties();

			if( this._backgroundCustomDepthMaterial ) {
				this._backgroundMesh.customDepthMaterial = this._backgroundCustomDepthMaterial;
			}

			if( this._backgroundMaterial ) {
				uniformOrUserDataTransformer( this._backgroundMaterial, 'frameSize', this._backgroundMesh.scale );
			}

			this._transferToBackgroundMesh();

			this.add( this._backgroundMesh );

		}

	}
@internal
@param {Mesh|Array.<Mesh>|null} mesh