@Greg_Ward can you explain why is the oconv command is complaining below:
$ obj2rad house_room2.obj > house_room2.rad
$ oconv house_room2.rad > house_room2.oct
oconv: fatal - (house_room2.rad): undefined modifier "m0_material_0"
I found a similar question in the following link obj2mesh -> oconv question but I do not really understand whether there is a relation or not.