   offsetting a texture coordinate for a cubemap
  Basically, I want to multi-sample my shadow map, which consists of a cubemap that stores depth information from the lights point of view.  At the moment, I just make a plus (3D plus rather) and get +/-1 X, +/-1 Y, and +/-1 Z.  This works mostly ok, except you end up getting a coordinate on the reverse side of the shadow map sometimes.I know my texture coordinate for the cubemap is a vector that points to a location on the box.  I want to make a plus projected around THAT point, instead of just a generic plus.  I just want that plus (only need 4 points there, since I'm basically translating it to 2D), to get my multiple samples.Does this make aaaany sense to anyone?  I just got into work and am tired from the bus ride, so hopefully I'm making at least a little sense.Thanks   
  Any ideas anyone?Basically (trying to simplify what I said), if I have a view vector to use as a texture coordinate, I want the up and side vectors from that view vector.  I can easily consider it as my Z vector, and calculate the X and Y vectors using the cross product, OUTSIDE of my shader, but I need to do it inside, how do I calculate these cross vectors properly.   