   How to do defered lighting without precision problem
  hi:  i'm making the effect of deferer lighting, but there is something i couldn't work out.  when i reverse the world coordinate of the vertex , it turned out to be a little different with the original vertex due to the limited precision .  And the ps 3.0 and vs 3.0, the output z buffer is 32 float .  So , how could i fix the bug ?  any idea is appreciated!!!   
  What format is the buffer that stores the world coordinates?If you're using 16-bit floats, it should work with minimal precision problems.   