This option allows you to add a complexity field and absolute checkbox to an object. This is useful for Bézier-based objects such as Extrude, Lathe, Bézier patch, etc.
The value entered in the numeric field is the percentage of complexity, or amount of detail, with which the object is rendered, either in the Modeling window or in the final image (in Raytracing and Raydiosity). It does NOT change the complexity of the object (which is defined mathematically), but only the way the polygon renderers (Scanline and OpenGL) display it.
To remove a Complexity attribute, select the object, then select Delete Attribute > Complexity Attribute in the Plus menu of the Project window.