User Experience Improvements to Pathfinder 2021.1

Posted on February 23rd, 2021

Pathfinder will also benefit from feedback from our users. This release focuses on incorporating their suggestions in to our products to improve the user experience. We have made several usability improvements to Pathfinder in the 2021.1 release, some of which are mentioned below. You can view the full list on the Pathfinder Release Notes page after the release on February 24th.

Added copy/paste functionality to Occupant Profiles

Expanding upon the functionality that we added to copy and paste geometry in Pathfinder 2020.1, we added the ability to copy and paste Occupant Profiles between separate Pathfinder instances. This means that users will no longer have to re-define the same profile in separate models, and can instead copy the profiles from one model to another. This is especially useful if users have several different profiles that are commonly used across a large number of models.

Added as-you-go undo/redo support for the Add a Polygonal Room tool

Similar to the changes to the wall and slab tools that we mentioned in our post about User Experience Improvements to PyroSim in 2021.1, we have added as-you-go undo/redo support for the add a Polygonal Room Tool.

Now, if a user makes a mistake when drawing a complex room shape, they will no longer have to start drawing that room from the beginning. They will have the ability to undo/redo any of the points they have drawn. This is especially useful for users that commonly draw their Pathfinder models on top of a 2D floorplan. You can see a short gif of this feature below.

Enhanced Monte Carlo user manual now available under the “help” menu

The Monte Carlo utility packaged with Pathfinder can help create models with randomized occupant positions and properties. This allows users to create multiple randomized copies of a model, run them sequentially, and process the resulting data set for research or regulatory requirements. The User Manual for our Monte Carlo command line utility is now available both online and in the application help menu.

Scripted Screenshots

We recently added the ability for users to interact with the Results viewer of both Pathfinder and PyroSim to generate a series of screenshots based on views that are defined in the Results view. This is particularly for users that generate reports from a series of commonly used views, as it removes the tedium of manually creating these screenshots in the Results UI. You can read more about this feature in Section 2.16.4 of the Results User Manual.

Monte Carlo Improvements in Pathfinder 2020.5

Posted on November 13th, 2020

Since Pathfinder 2018.3, users have been able to take advantage of Monte Carlo simulations through a command line interface. In modeling, the Monte Carlo method is used to randomize inputs across many simulation instances. With a statistical analysis applied, users can create probablistic interpretations of the resulting data sets. It is often used in research and is also required by regulations such as RiMEA. … Read More

Mars Colony Biome Evacuation Analysis by Szymon Matkowski

Posted on August 11th, 2020

Our support team has been assisting Szymon Matkowski with his recent project based on a feasibility study, completed by a team at Wroclaw University of Science and Technology, of possible layouts and technical solutions for a theoretical base on Mars. The study was part of a competition sponsored by The Mars Society in which the team at Wroclaw won second place. In Matkowski’s study, he analyzes evacuation of a Mars colony biome under threat of decompression or fire.

Diagram of Twardowski Colony Biome Evacuation
An overview of Matkowski’s evacuation plan based upon the Wroclaw team’s design.

Safety of the people is a top technical priority in every building or device – in any place. All: structure, MEP systems and the layout should be focused on minimizing the risk of life loss. Design of a base, or colony on other planet also should comply with this principle. The layout of all safety egress communication (passages, corridors, staircases, lifts etc.) should not be changed or altered. The unchangeable layout of those elements is a bone system for the functional layout and all the decoration we see. The drawback of such solution is that – once designed the layout is frozen. Any change leads to re-examination of all safety measures – which is very expensive (even in Earth’s conditions). One of the most important coefficients is evacuation time. Time – which people have to save their lives. This blog entry describes my research on Evacuation movement speed on Mars and a sample evacuation time count. Depending on the threat (decompression, fire and smoke) additional means should be provided : smoke exhaust, additional air supply, sealed safety rooms, emergency teams access routes and action plan. For the purpose of the investigation I have used a fragment of Twardowsky Mars Colony. Twardowsky won 2nd prize in 2019 competition organized by Mars Society. You may see the presentation here. Also the competition entry of the Base was published in a book.

During Matkowski’s analysis, which he completed in less than two months as his first Pathfinder project, many challenges were addressed. This included approximating the speed adjustment with Mars gravity and with various space suit equipment, behavior adjustment upon triggering events such as decompression, and the simulation of airlocks with pressurization phases. The Thunderhead Engineering support team aided Matkowski throughout these challenges which led to his successful analysis.

You can read Matkowski’s full analysis for free on the website.

Social Distance Improvements in Pathfinder 2020.3

Posted on August 7th, 2020

Pathfinder 2020.3 further enhances the user’s ability to model social distance behavior as a method to address pandemic safety. Social Distance has been completely separated from Comfort Distance. Now, rather than Enable Forced Separation in the Simulation Parameters (retained in 2020.3 for legacy files), Social Distancing has its own selection field in the Advanced tab of the Edit Profiles dialog. With this recent development, occupants exhibit less “jostle” or “jitter” while smoothly and effectively maintaining distance. … Read More

New Pathfinder Data Options to Assist with Coronavirus Scenario Modeling

Posted on April 7th, 2020

* The features described in this article are now available in Pathfinder 2020.2 and later versions.

The global spread of the SARS-CoV-2 virus and associated COVID-19 sickness has profoundly changed human interactions in a matter of weeks.  It will likely be several more weeks until the first wave of illness is under control. 

Modeling how these interactions affect our environment will provide insight into what can be done to improve public safety now and in the future. Thunderhead Engineering has implemented additional analysis tools in Pathfinder to assist with evaluation of various human movement scenarios.  

Discussions with current customers that perform crowd modeling led us to focus initially on improved data output and visualization related to the minimum distance between agents in a simulation.  Maximizing the closest distance between occupants and minimizing the total number of occupants encountered has the potential to reduce overall risk when comparing alternative layouts or procedures for a space.

These changes are the beginning of rapid development in Pathfinder intended to help model and visualize important emerging scenarios:

  • Immediate changes to public spaces will need to be vetted quickly to determine the best methods of reducing transmission.
  • After the first wave, governments, factory managers, and administrators of public spaces will need tools to evaluate risk levels and exposure as these spaces are slowly reopened at reduced capacity. 
  • Increased physical distance within commercial and public spaces will likely be needed for several months. 
  • As pockets of illness reappear, space planners will want to be prepared with alternate plans that can minimize virus transmission while avoiding widespread full closures of facilities.

Pathfinder Changes

Output Data for Social and Physical Distancing

In this preview build, Pathfinder.exe supports a new command-line parameter:
(2.0 is a value in meters that can be adjusted to control some of the following features)
This parameter activates writing of the following new data files:
  • CSV-format output file modelname_sd_transient.csv  containing transient data about occupant separation. For every time and occupant in the simulation, the closest other occupant is listed along with distance.  Additionally,  the number and ID of occupants within 1m, 2m, and 3m are also listed.  The presence of the social_distance command line parameter is required for this output to be generated, however adjusting the numeric value of social_distance has no impact on this output.
  • CSV-format output file modelname>_sd_accumulated.csv containing accumulated exposure data for each occupant.  For every occupant in the simulation, the occupant who has spent the longest time within r=social_distance is listed, including the occupant ID and the total amount of time.  Additionally a count is made of all occupants who have remained within social_distance of the occupant for more than 1 minute and 5 minutes, including the occupant IDs.

Graphical Depiction of Social/Physical Radius

When Pathfinder.exe is run with the social_distance command-line flag, Results will display a disk at the base of each occupant whose radius is social_distance meters. In addition, a Debug menu will appear on the menu bar enabling the use of the Edit Debug Options… dialog where you can edit the value of Social Radius (note: set the value to zero to disable this setting).

New Occupant Contours to Quantify Exposure

We have implemented two new Occupant Contours in the Pathifnder Results viewer that may help evaluate physical distance between occupants — currently named Social Linkage and Social Usage.  
  • Social Linkage uses a given radius (R) to calculate how many other agents are within that radius and plots that as the value drawn inside a circle of radius R centered at the occupant.  Higher values display on top of lower values.  We are also considering displaying this measure as a per-occupant color for greater clarity.
  • Social Usage is similar to a density contour and is referenced to the contour mesh.  For every point on the mesh (conceptually a spot on the floor), the number of agents within radius R are calculated and assigned to that mesh point.  The mesh of all values is then contoured.  This will give the high values between the agents rather than right at the agents.

It is also possible to use the existing Density or Usage contours in Pathfinder to show different data if you consider how the calculation is done and what scale is used.  Since the Usage contour assigns a value that ranges linearly from 1 at the agent location to 0 at radius r, it can be used to draw range rings.  In this example with r=3 and three color bar segments, the green circle represents 2m from the occupant and red shows 1m.

Additionally,  all contours can be passed through filters to display average or maximum values over time.

Help with Pathfinder Preview Feedback

* The features described in this article are now available in Pathfinder 2020.2 and later versions.

These preview features are preliminary and are subject to change before an official release of Pathfinder.  However, our goal was to make these updated data options available as soon as possible for anyone evaluating procedures and space usage during the current crisis.  We encourage anyone interested to contact and try out these new features.  At the present time, we are prioritizing feature development in Pathfinder that focuses on improving simulation or data analysis for social distance modeling.  Please let us know if you have requirements or suggestions to help us build a tool that can help improve public health and reopen buildings in a responsible manner.

Vertical Ladders in Pathfinder

Posted on April 1st, 2020

We recently had a question about modeling vertical ladders in Pathfinder. This post will describe the details of how to accomplish this. This question came from Saqib Mehmood of Aalborg University in Denmark, who was modeling wind turbine evacuation. Saqib Mehmood was joined on this project by a team including Anders S. Kristensen, Francisco Manuel Dieguez Barreiro, Hana Softic, and Yannan Zhou.

Vertical ladders imported into Pathfinder to model wind turbine evacuation.


Figure 1 shows normal stairs. Each end of the stairs must connect to boundary edges of the rooms. If the stairs connect the interiors of the rooms, cutouts at the top and bottom must be used, Figure 2. The top cutout must be larger than the occupant radius and stairs cannot be truly vertical, there must be some slope. The walking surface is naturally defined as the top surface of the stairs.

Figure 1: Normal stairs connecting two rooms.
Figure 2: Cutouts required for a stairs that connects center of rooms.

Pathfinder does not have ladders, but ladders can be represented as steep stairs. Figure 3 shows ladders connecting two floors.

Figure 3: Model of ladders connecting two rooms.

In this model, the distance between floors is 20 m. The cutouts in the top and bottom floors are vertically aligned and measure 1 m by 0.5 m. Because the ladders connect to opposite sides of the holes, there is a slight slope to the ladders. The walking surface of the ladders is the face of the ladder whose normal has a small positive Z component. 


We want to specify occupant speed on a ladder. By default Pathfinder modifies the speed on stairs based on the approach described in the SFPE Engineering Guide – Human Behavior in Fire, 2003. These values are not appropriate for a vertical ladder, so we will use a stair speed modifier to obtain the desired value.

As described in the Pathfinder Technical Reference section Path Following in SFPE Mode, the occupant base speed, v_{b} is given by:

    \[v_{b}=v_{max}\star v_{f}(D)\star v_{ft}\]

where v_{max} is the occupant’s maximum speed entered in the user interface as Speed, v_{f}(D) is the density speed modifier, and v_{ft} is the terrain speed modifier.

v_{ft} is defined as 


where k=1.4 is the value for level terrain. For stairs, the value of k depends on the stair riser and tread that is input in the Pathfinder user interface, Figure 4. Note that k is not calculated using the physical stair geometry, it is calculated based on the user input. For our purposes it is sufficient to know that a stair with a rise of 19.0 cm and a tread of 25.4 cm gives a value k=1.0.

Figure 4: Stair parameters.

On steep stairs the density is low so the density modifier v_{f}(D)=1.0. For a stair with rise of 19.0 cm and tread of 25.4 cm k=1.0, so the occupant speed is given by

    \[v_{b}=v_{max}\star \frac{1}{1.4}\]

We can multiply v_{b} by a stair speed modifier to obtain the desired ladder speed

    \[v_{ladder}=modifier\star v_{b}=modifier\star \frac{v_{max}}{1.4}\]

By default Pathfinder v_{max}=1.19 m/s and if we desire a ladder speed of 0.25 m/s, then the speed modifier=0.294.


We run the example using the stair parameters shown in Figure 5. We also select some occupants, click the More button, and enable csv output of individual data.

Figure 5: Stair parameters used in the simulation to give a ladder speed of 0.25 m/s.

Figure 6 shows the initial positions of the occupants and Figure 7 shows the occupants descending. 

Figure 6: Preparing to descend.
Figure 7: Descending. Note that the occupants face in the direction in which they entered the stairs.

We can open the csv file for the ladder with the single occupant and see that the speed on the ladder is 0.25 m/s. Similar results are obtained for the ladder with multiple occupants, with some initial stop/start movement as they adjust on the ladder.

Figure 8: Speed of descending occupant.

Additional Comment: In this example, I used the stair speed modifier to control the ladder speed. An alternate approach would be to change the speed/density curve for stairs in the occupant Profile. This has the advantage of allowing a single profile to represent different speeds up and down the ladder. It has the disadvantage that it affects speeds on normal stairs also.

Download File

You can download the Pathfinder model here.

ladder post

1Point2 Studies Bathrooms and Gender Bias in France

Posted on December 5th, 2019

1Point2 is the official partner of Thunderhead Engineering in France and has been since 2014. For over 30 years they have specialized in dynamic flow simulation for industry, transport, and construction. As an early pioneer in simulation, 1Point2 provides consultation services through the acquisition, training, implementation, and post-analysis of simulation software tools. Not only do they distribute and support flow simulation software, including localized PyroSim and Pathfinder each with bilingual French/English interfaces, they also use these tools for model building and flow studies.
Their team recently completed one such study in which they examined the problems that arise when gender specific bathrooms are not uniquely designed to meet the needs of its typical occupancy. Particularly, women were seen to experience longer wait times for their bathrooms. Jacqueline Gélinier, Product Manager at 1Point2, further examines what impact this can have on professional women compared to their male peers. Read the full article on the 1Point2 website.
Bathroom Gender Study by 1Point2

Change Profile Dynamically with New Behavior Step

Posted on November 19th, 2019

Coming soon in Pathfinder 2019.3 we will see a new Behavior step that allows occupants to dynamically change their Profile. A similar feature was added previously where occupants could change their behavior. The profile contains the occupant’s characteristics such as speed, door choice, and various settings related to interacting with other occupants in the model. 

Profile Dialog

You can adjust the behavior step to assign a specific Profile, or to randomly assign one of many options from a defined distribution. This is similar to how changing behaviors works. 

There are many possible uses for this new feature. Occupants could move from a healthy profile to injured or fatigued. Occupants with limited mobility can switch from walking to wheelchair assisted movement. We’re curious to hear what ideas you have for this feature, so please feel free to contact us.

Save Settings for Results Visualizations

Posted on October 30th, 2019

The most recent release of the PyroSim and Pathfinder Results application allows users to create, save, and load results visualizations. A results visualization is a collection of settings that define which Pathfinder and FDS results are to be loaded and how those results are to be displayed. It also contains information entered by the user, such as views, tours, colorbar settings, time settings, annotations, object visibility, etc.

Results visualization files end with either .pfrv when saved from Pathfinder Results or .smvv when saved from PyroSim Results. When Pathfinder or FDS results are viewed from either Pathfinder or PyroSim for the first time, a results visualization is automatically created and saved containing the results data. The visualization file name will match that of the originating PTH or PSM file.


You can create multiple visualization files with different data sets (FDS and Pathfinder) and different saved states. This allows a user to reuse previous settings and to save particular visualization configurations for the same data set. This new feature also simplifies file management, as there is now a single visualization file with information that was previously stored in 3 different files (*.pfrmeta, *_resultsviews.json, and *_session.json), along with additional information that was not saved before.

The first version of results visualization available now allows you to save most settings. The rest will follow suit in the last release of the year.

Data Visualization through Occupant Colors in Pathfinder 2019.1

Posted on June 13th, 2019

Pathfinder 2019.1 introduces an additional way to visualize evacuation results through the color of occupants in the model. Occupants can be assigned a dynamic color value based on criteria such as behavior, profile, speed, and more. The video below illustrates many of these options within a single model.

This information can be combined with other displays such as occupant contours, dimensions and labels, or fire and smoke visualization.