Hello, for the production of villas/duplex buildings, or basements (the first floor is regarded as the basement, and the second floor is regarded as the first floor)}, the following methods can be referred to:

Method 1. Build the indoor structure with columns and platforms;

For the indoor villa tutorial, please click: https://www.aihouse.com/global/study/detail/641 

Method 2. Draw the indoor structure using the free modeling function;

please click:  https://www.aihouse.com/global/study/detail/492