export double sided polygons

How can I export a mesh to VRML or .obj that contain double sided polygons? Allthought The mesh is rendered as two sided both in the 3D view and when rendered in blender when I export it to any fileformat, the polygons are just onesided. The outer part is one invisible. I created the mesh with a simple cyliner and delted some faces. The normals point outward.

dose obj or VRML supports double sided polygons?

i have no clue. I am acutally not constraint to any format, since I have PolyTrans. All I want is import double sided geometry to PolyTrans.