Figure 4: A simple building model and the corresponding navigation mesh
As can be seen in Figure 2, obstructions in Pathfinder are represented implicitly as gaps in the navigation mesh. Since occupants can only travel on the navigation mesh, this technique prevents the overhead of any solid object representation from affecting the simulator. When the navigation mesh is generated by importing geometry, any region of the mesh blocked by a solid object is automatically removed. For overhead obstructions, the mesh generator considers any obstruction within 1.8 meters (6 feet) of the floor to be an obstacle.
Geometry Subdivision
The navigation geometry is organized into rooms of irregular shape. Each room has a boundary that cannot be crossed by an occupant. Travel between two adjacent rooms is through doors. A door that does not connect two rooms and is defined on the exterior boundary of a room is an Exit door. There can be multiple exit doors. When an occupant enters an exit door in SFPE mode, they are queued at the door and removed at the flow rate defined by SFPE. Occupants that enter an exit door in reactive steering mode are removed from the simulation immediately.
Figure 3 illustrates these concepts for the IMO Test 10 problem. The rooms (and corridors) are shaded different colors. Doors from individual rooms to the corridor (just another room in the