Thanks for all your comments !
tyrellcorp : For the cracks, i mainly use the clay tubes, and sometimes the planar cute,gouge or standard (it depends of what kind of rock you are working on). I truely love working surfaces, especially those ruins stuff!
NEX is only used to build your ingame asset by using the HD geometry. You manually create the topology by placing points over you HD model, and then build polygons ! , but you have to decimate the HD before importing it in Maya otherwise your computer will be very slow
Uncharted was a source of inspiration ! One of my favorite game ever ! They ruins are simply amazing ! Just can’t stop playing uncharted 2