Pathfinder 2013 includes changes to the behavior mode settings. This post outlines those changes and includes videos to help illustrate the differences.
Pathfinder 2012 gave the option to run simulations in three different behavior modes:
- Steering mode (default) – this mode offered the most realistic looking movement, but a lack of door flow rate limits often produced exit times that were faster than the SFPE handbook suggested.
- SFPE mode – this mode gave answers similar to the SFPE handbook, but didn’t use any collision detection (or avoidance) and looked very artificial.
- SFPE mode with collisions – it was also possible to create a hybrid mode by enabling a simple collision model in SFPE mode, but without the occupants avoiding each other this mode was problematic.
The following video shows each of the three modes running side-by-side in Pathfinder 2012:
For each of the three runs, the model was identical except for the behavior settings. The video shows SFPE mode (left) occupants collapsing into an impossibly tight pattern, the steering mode (right) occupants exiting much more quickly than the SFPE-based approach, and the hybrid mode (center) appearing to have the best of both worlds. Unfortunately, the hybrid mode struggled with corners, as we can see in the next video:
The hybrid mode takes longer to finish because occupants packed up at the edge of the door and only allowed a single column of occupants to move through a larger space. This is a consequence of enabling collisions without including collision avoidance AI.
Pathfinder 2013 introduces the following changes:
- Steering mode now uses slower acceleration for occupants. Previously, occupants could reach their maximum velocity in 0.5 seconds, the new default is 1.1 seconds. Now this value is editable in the profile settings.
- SFPE mode with collisions has been removed. Instead, the flow rate through doors can now be controlled in steering mode. This flow rate limit is not enabled by default.
In short, steering mode gives exit times that are more similar to hand calcs and SFPE with collisions has been replaced by Steering with door flow rate limits.
This video is the Pathfinder 2013 version of the three modes, side-by-side comparison:
If we consider the time at which the last occupant passes through the first door, Pathfinder 2012’s steering mode was 44% faster than the SFPE mode. In Pathfinder 2013, this difference is only 8% – a change we attribute to the change in acceleration.
The hybrid mode now takes more time than the SFPE mode, as it must account for both the sudden stop associated with flow rate limits and acceleration (i.e. being forced to wait a single time step by the flow rate limit forces the occupant to start over from zero velocity).
The advantage of the new hybrid mode becomes clear when we see how it eliminates problems that the old hybrid mode (SFPE with collisions) had with obstacles. This video compares SFPE mode to hybrid mode in Pathfinder 2013 in the same cornering case shown above.
The appearance of occupants moving through the doorway is greatly improved as occupants use the full width of the doorway. In Pathfinder 2013, the hybrid mode takes 6 seconds longer than SFPE mode, where the previous generation’s hybrid mode required 9 more seconds than SFPE mode.