isOccluded( object ) {

		const renderContext = this._currentRenderContext;

		return renderContext && this.backend.isOccluded( renderContext, object );

	}
This method performs an occlusion query for the given 3D object.
It returns `true` if the given 3D object is fully occluded by other
3D objects in the scene.

@param {Object3D} object - The 3D object to test.
@return {boolean} Whether the 3D object is fully occluded or not.