Method roughness

src/model/RoofVegetation.cpp:76–80

    }

    std::string RoofVegetation_Impl::roughness() const {
      boost::optional<std::string> value = getString(OS_Material_RoofVegetationFields::Roughness, true);
      OS_ASSERT(value);
      return value.get();
    }

    double RoofVegetation_Impl::thickness() const {
      OptionalDouble od = getDouble(OS_Material_RoofVegetationFields::Thickness, true);