Hey,
Sorry that it took me so long to reply to your detailed description of the problem. As I said, I don't specify normals explicitly in obj, they are derived from the vertex order. Yes, I can add an option to reverse that order. Or I can specify vertex normals and that will also allow me to implement smooth surfaces. I'll try both options next time I update City Viewer or Procgen mansion. Maybe I should buy TTS, it's not expensive...