Hi all,
I just downloaded UDK ( Unreal development kit ) and I’m starting to work with that, but I got some import mesh problems, because when I try to add the mesh inside the UDK editor their position is not the same that is in XSI, so what I need to do is, for each mesh, to put their pivot to the center fo the grid ( basically 0,0,0 ).

Is there a way to do that for every mesh by selecting them and do some operation? I mean, I can do that all at once or I need to select each one and reset the pivot manually?

If you want the center to be 0,0,0 but to have the models offset (handy when building props specific to a room, as you only have to place one actor to have the rest automatically placed correctly), you can just select all the models, expand the Transform menu on the main control panel (to the right of the screen), and chose to freeze all transforms. This should give every mesh that was selected a center of 0,0,0

If you want to manually place the center/pivot (such as for a single, reusable actor), I usually:
-- select the object (make sure COG is turned off)
-- go to Transform>move Center to Bounding Box
-- switch to center manipulation (top right of the screen, or just hold alt)
-- turn on snapping (or hold ctrl), y-value only
-- snap to the lowest vert on the mesh
-- switch back to object manipulation mode, and zero-off the translation

And if there is a specific vert you want to serve as the center, then it becomes really easy as you can either use Transform>Move Center to Vertices, or alt+ctrl click to snap the center there.