getNextRenderItem( object, geometry, material, groupOrder, z, group, clippingContext ) {

		let renderItem = this.renderItems[ this.renderItemsIndex ];

		if ( renderItem === undefined ) {

			renderItem = {
				id: object.id,
				object: object,
				geometry: geometry,
				material: material,
				groupOrder: groupOrder,
				renderOrder: object.renderOrder,
				z: z,
				group: group,
				clippingContext: clippingContext
			};

			this.renderItems[ this.renderItemsIndex ] = renderItem;

		} else {

			renderItem.id = object.id;
			renderItem.object = object;
			renderItem.geometry = geometry;
			renderItem.material = material;
			renderItem.groupOrder = groupOrder;
			renderItem.renderOrder = object.renderOrder;
			renderItem.z = z;
			renderItem.group = group;
			renderItem.clippingContext = clippingContext;

		}

		this.renderItemsIndex ++;

		return renderItem;

	}
Returns a render item for the giving render item state. The state is defined
by a series of object-related parameters.

The method avoids object creation by holding render items and reusing them in
subsequent render calls (just with different property values).

@param {Object3D} object - The 3D object.
@param {BufferGeometry} geometry - The 3D object's geometry.
@param {Material} material - The 3D object's material.
@param {number} groupOrder - The current group order.
@param {number} z - Th 3D object's depth value (z value in clip space).
@param {?number} group - {?Object} group - Only relevant for objects using multiple materials. This represents a group entry from the respective `BufferGeometry`.
@param {ClippingContext} clippingContext - The current clipping context.
@return {Object} The render item.