So I exported http://sketchup.google.com/3dwarehouse/details?mid=f7d9d34e3d74d0c739f3410d5f76299b&prevstart=0 as an .obj file and when loading it in an OBJ viewer (e.g. Meshlab), it appears that there's duplicated geometry... Is this a problem with the model or with Sketchup's exporting function?