Hello , thank you for answering ( and congratulations on this programme !)
i wanted to import the scene to COPPERCUBE ( ambiera.com) , a 3d authoring tool; it seems that it can't read the generated MTL file properly... The external texture files ( for walls and floors ) are read correctly. I put everything in the same folder before importing.

In Coppercube , the objects ( a bed for example ) are there , but all black.

I read that Coppercube has issues interpreting mtl files when there are spaces but removing all spaces from the .obj and the .mtl has resulted in a big black box....

I think I'll use sweet home 3d for designing the rooms , but i will include furniture after importing to coppercube. ( objects from ggogle 3d warehouse or something , I think they are free to use)