Yes I have the REVIT model but I am not sure exporting to an obj file is a good idea in my case. Correct me if I am wrong but from what I know it will be nearly impossible to detect colisions with the with walls and doors. The basic idea of the game is to explore the building and find hidden object. For that I can't lose the information I have on revit about the doors location for example
From my point of view it's doable, but I have been working with Revit API for some time now. From API you can do a lot, you can even export separate elements to separate files. You don't have to export to obj, it's just example. The main problem here is writing your own exporter. I have no idea how much experience you have, but here's my first idea:
Revit works on Elements, door is example of such element. You can filter elements to get only doors. You can create level file (for instance in XML or Json) which will store world transform of a door and it's model name/id. While loading the building in you game, you can use such file to find and place doors with your door physics behaviour.
Note it's just quick idea so it can have a lot of flaws
When you talk about rendering: it is possible to bring the model to Blender via .obj for example and use it to adjust textures and UV maps and bake lighting into the model textures.
This. In case of Revit you need to write your own exporter (as ExternalCommand in Revit Add-in). Chances are that UV will be messed up. I think that using 3D editing tool for post processing will be a must. Another problem that could appear is that geometry could be 'overtessellated', so you probably will want to optimize things a bit.
Doesn't your BIM application support exporting to common 3D file format (3ds, fbx, collada, ase, obj)? Which BIM app you want to use? I rendered a building from Revit in my DirectX app no problem, I just exported it from Revit as obj and loaded with Assimp.
I noticed you mentioned Revit in tags. If you worked with Revit you should know Jeremy Tammik's blog, here's a post on Revit 2014 obj exporting: