A system and method for displaying objects in a plurality of layers. The layers are distinguished from one another using a variety of display attributes in order to emphasize objects in upper layers and de-emphasize objects in lower layers. The display attributes may include use of color (hue, saturation,...http://www.google.com.hk/patents/US7187389?utm_source=gb-gplus-share專利 US7187389 - System and method for simultaneous display of multiple object categories
