You just draw your project. Don't worry about the rest.

  After openning your project which is drawn by AutoCad  etc. cad  programmes and saved as DXF file Auto3dNow transform it into 3D depending on the starting parameters.Walls are formed, window and door opennings are created and doors and windows are placed into. Wall and floor coverings are created. You can walk around in that 3D media by using arrow buttons. Or on a path drawn by the mouse you can move camera. With a one mouse click you can change wall, floor and celling coverings.  You can use different windows or doors. In addition to that again with a mouse click you can add light or 3D material. 

   You can draw staircase, cupboard, etc. or even garden by AutoCad etc. Then you can enrich your project by adding coverings to these.