It's mainly for vegetation like this trees. This shot is from my rendersoftware:



As you can imagine, looks not this good when the branches in the back are rendering in front of the trunk

trueSpace 7.6, A7 commercial
Free gamegraphics, freewaregames http://www.reinerstilesets.de
Die Community rund um Spiele-Toolkits http://www.clickzone.de