uploading a 2D floor plan for a floor of a building and storing the 2D floor plan on a server having a processor and a memory;

executing a server program on the processor on the server, the server program generating a 3D model for the floor by extending upward polygons and lines generated by the server program vectorizing the 2D floor plan, wherein the polygons and lines are extended upward by a floor-to-ceiling height entered by a user;

the server program storing walkable flags that are set by the user for rooms and exits in the 3D model for the floor, a walkable flag indicating that the room or exit is walkable in a navigation network;

the server program linking together rooms and exits in the 3D model for the floor that have the walkable flag set to form a navigation network for the floor;

the server program generating a plurality of the 3D model for the floor for a plurality of floors in the building, the server program also generating a plurality of the navigation network for the plurality of floors;

the server program stacking the plurality of the 3D model for the floor and the plurality of the navigation network to form a 3D building model, wherein floors are separated by a floor-to-floor height input by the user;

the server program receiving floor connection nodes that are specified by the user for stairs, elevators, or escalators that connect together different floors in the plurality of floors;

wherein each floor connection node specifies a first floor and a second floor that are connected by an elevator, escalator, or stairs;

the server program connecting the navigation network for the first floor in the plurality of floors to the navigation network for the second floor in the plurality of floors for each floor connection node; and

the server program outputting the plurality of navigation networks for the plurality of floors with the floor connection nodes connecting different floors as an indoor navigation network, the indoor navigation network for defining walkable routes through the building.