New Preferences for Snapshot Defaults

Posted on March 30th, 2022

Pathfinder 2022.1, the first release of the year, will soon launch with a new minor feature which provides an option to enable or disable simulation snapshots from the Preferences menu. … Read More

Build Stadiums and Theaters with Inferred Stairs

Posted on December 9th, 2021

What are Inferred Stairs?

Sometimes Pathfinder models include stair access for occupants which are modeled without any of the user-defined stairs tools. In Pathfinder 2021.4 this modeling technique is automatically detected and occupants traversing the stairs now move according to stair behavior appropriate for the determined riser and tread distances. With the inferred stairs feature, Pathfinder users now have more flexibility in creating complex stairs without sacrificing in movement accuracy.

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Improvements in Pathfinder 2021.4

Posted on December 1st, 2021

Pathfinder 2021.4 focuses on improving seating ingress through occupant targets and improving accuracy through advanced stair movement calculation. Additionally, this Pathfinder release is supported by Results improvements which incorporate gamma correction for improved lighting.
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Occupant Targets add Seat Reservations to Pathfinder

Posted on November 12th, 2021

In Pathfinder 2021.4 we will introduce a new object for occupant behaviors called a Target. Occupant targets represent a 1-person location which can be reserved by an occupant through a behavior action. This location remains assigned to the occupant even if they temporarily depart, unless a behavior action triggers them to Abandon the target. Targets are an excellent choice for modeling seating for entertainment venues such as stadiums, auditoriums, or theaters as well as waiting lobbies for medical, commercial, or transit locations. … Read More

New Terminal Behavior Action Types

Posted on September 27th, 2021

Pathfinder 2021.3 introduced Attractors, a tool for providing awareness-based detours. In order to achieve this new Behavior, additional action types were needed. In total, there are 3 new terminal step types, which are behavior actions which can be used as the final action in a behavior. In addition to Goto Refuge Rooms and Goto Exits, the following actions may now be used. … Read More

Improvements in Pathfinder 2021.3

Posted on September 1st, 2021

Pathfinder 2021.3 focuses on improving multi-project management and improving dynamic occupant behavior for advanced applications. Additionally, this Pathfinder release is supported by Results improvements which incorporate technology advancements in video rendering. … Read More

Attractors Preview for Pathfinder 2021.3

Posted on August 6th, 2021

Restrooms modeled with Attractors in Pathfinder 2021.3.
Occupants in a waiting room utilize the nearby restrooms as needed via the new Attractors feature.

Pathfinder 2021.3 introduces Attractors as a brand new way to allow occupants to interact with objectives outside of their main behavior. Perhaps some airline passengers are tempted by a cafe on their way to their gate, museum attendees are swayed to visit the gift shop, or subway commuters have a few spare minutes to use the restroom before their departure. In each of these scenarios, there is some percentage of the population which will be attracted to a secondary objective. … Read More

2021.2 Patch Release – Available Now

Posted on May 26th, 2021

One of our Reseller Partners identified an issue when dragging items in the navigation view. When this happens, the application freezes and requires a forced shutdown to proceed. This issue was introduced in the 2021.2.0512 release of both PyroSim and Pathfinder. 

We have identified the problem, and have uploaded patch releases that addresses the bug. The updated versions of PyroSim and Pathfinder are available now.

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Improvements in Pathfinder 2021.2

Posted on May 10th, 2021

Pathfinder 2021.2 introduces queueing as a new behavior which can greatly expand modeling options and capabilities. New user interface enhancements make it quicker than ever to find objects and edit properties.
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Proximity Analysis and the Thunderhead development process

Posted on April 29th, 2021

The upcoming release of Pathfinder Results version 2021.2 will include a Proximity Analysis feature based on the paper EXPOSED: An occupant exposure model for confined spaces to retrofit crowd models during a pandemic by Enrico Ronchi and Ruggiero Lovreglio. In the paper Enrico and Ruggiero lay out a method to create metrics that measure occupant exposure in microscopic scale environments, which enables evaluation of the efficacy of infection mitigation measures. In simpler terms, they supply a way to measure how effective social distancing measures are at preventing the spread of disease. This post will lay out our development process to create this and other features and summarize the proximity analysis feature as implemented in version 2021.2.

The Thunderhead development process

At Thunderhead Engineering, we have periods of time that we call “Project Phoenix” where developers can work on any project that is interesting to them, whether it is a marketable feature or just a fun research project. During our Project Phoenix iteration last June, two of our interns worked on a project involving tracking the spread of an infectious disease in a Pathfinder model. This initial project modified the Pathfinder simulator to produce a simple SIR-like model during occupant movement.

After this project was completed, our team discovered Enrico and Ruggiero’s paper. After speaking with Enrico and showing him their prior project, our interns and the rest of the development team decided to modify the project to reflect the paper’s suggestions and implement it as a new feature in our Results viewer. After 3 iterations of the project, and some help from the rest of our development team, the proximity analysis feature is ready for release.

What is Proximity Analysis?

Unlike the first iteration of the project, the Proximity Analysis feature shipping in the upcoming 2021.2 release does not modify the Pathfinder simulator. Instead, it post-processes the output of Pathfinder simulations in our Results program. The Results Viewer generates a proximity analysis report that provides various metrics regarding occupant exposure, including the amount of time that k number of occupants are within a proximity radius of another occupant, how many occupants are violating the proximity radius at any given point in time, and a global exposure time metric. Because this feature is part of Results viewer and does not modify the simulator, users will not need to re-create or re-run simulations to generate Proximity Analysis reports. They can be generated using the results from any existing Pathfinder simulation.

Example Proximity Tracing Graph
Example of one of the graphs output by the new Proximity Analysis feature of Pathfinder Results 2021.2

How would Proximity Analysis be used?

One case where proximity analysis is particularly useful is when evaluating social distancing measures. By performing a baseline/control simulation, changes made to the Pathfinder model can be evaluated by their effects on the global occupant exposure metric to determine if the changes are effective in enforcing social distancing. This can also be used to compare different social distancing measures against each other to determine which ones are the most effective.


Our team enjoyed creating this new Proximity Analysis feature, and we look forward to continuing to improve our products. You will be able to access Proximity Analysis in the upcoming 2021.2 release. If you have any suggestions for features you would like to see in our products, you can email them to our Support team at and we will consider them.


Ronchi, Enrico, and Ruggiero Lovreglio. “EXPOSED: An Occupant Exposure Model for Confined Spaces to Retrofit Crowd Models during a Pandemic.” Safety Science, vol. 130, Oct. 2020, p. 104834.,