Using the cubemap probe entity
This is a short article on how the cubemap_probe works for Urban Terror's new Bumpy features. I must stress that this only works with any of the FS_q3map2_radbump.exes and which will only work when -radbump is used in the compile. If you do not have FS_q3map2_radbump.exe then you can find the latest update in the first post in this thread on the UrT forums, its a windows program but can run with linux under wine.
You will also need to add this to the bottom of your definition file for GTK, you should find this in /scripts/urbanterror.def