Urban Decay Textures Revisit in 3DsMax

Starting to relight the scene in 3DsMax. There was this problem with the walls, floor, and roof disappearing. Originally I thought it was a MR sun/IBL issue, so I thickened the geometry of the walls. It was just a matter of changing the settings for a few shaders. Above is the scene, the second version has final gather settings. There is a directional sun light (key) pointing into the open wall and a fill light.