   Should i Generate Shadow of Occluder's Back Face?
  Beg you help me. Thanks all!I write a simple code for shadow mapping.I find that this technique can give occluder's back face a shadow.Like this:http://farm4.static.flickr.com/3411/4640645927_5e665c066a.jpgBut i think that shadow is ugly and uncontrollable and hard to blur.I want to know that should you generate shadow of occluder's back face in usual?If not, what to do? Thanks!!!   
  Actually your shadow is ok. The problem is that you have not applied a lighting model to your objects. If you apply a simple diffuse lighting model (instead of the ambient model) then the back of your objects will be naturally dark, and you won't be able to see the ugly shadows.   