This 3D model was originally created with Sketchup 8 and then converted to all other 3D formats. Native format is .skp 3dsmax scene is 3ds Max 2016 version, rendered with Vray 3.00 This is because this 16-sided structure's walls and roof are trapezoids. The cupola roof is triangles. And yes, the exterior walls slant inward at the top. Just the ,um, bare necessities - rudimentary kitchen, bath with water heater, sleeping loft. In floor heating for the winter, casements and awning windows in the cupola for flow-thru ventilation in the summer. This could be used anywhere, from someone's backyard to deep in the woods, It is fully insulated. Design is from a cable show.