How to export mesh with tangents?

I can’t figure out how t export a scene or object to .3ds .x or .obj with tangents information… (for parallax mapping)
I tried export scripts included in blender with every option/combination but I still don’t have tangents…

or maybe there is an option/flag to trigger tangets on somwhere deep in Blender or maybe I have to use other file format?
How does it work in blender?