Try making the room invisible.  Get Z-depth render of the contents. In photo app, select and delete the white background.  Get a Z-depth render of just the room prop.  Overlay first render extract atop the second (room) render.

Just throwing out ideas;  don't know if it will help.

     I know it can be done;  I use it occasionally to create displacement maps for bas-relief carved panels.

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Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5