3D Unreal Engine Visualization Technology of WFDS Plot3Ddata for the Development of a Virtual Forest Fire Training Simulator

The deaths and injuries of firefighters due to forest fires occur continuously around the world every year.
Forest fire-related organizations are operating forest fire education programs to effectively suppress forest fires and prevent safety accidents for firefighters.
Firefighters must improve their ability to respond to each forest fire situation for effective suppression at the fire site based on their knowledge of the forest fire environment.
There are many differences from the actual forest fire suppression environment in theoretical learning and training on the nature of wildfires on a laboratory scale.
Building fire education and training simulators using 3D virtual reality technology and game-type forest fire suppression training programs are being developed.
The expression of flame and smoke is used by a training instructor to create each fire situation by adding a simple image as a fire icon, without applying chemical species and physical analysis.
This study proposes to develop a 3D virtual reality education and training authoring tool based on chemical species and physics analysis for more realistic forest fire field experience and effective education by firefighters.
This study proposes a technology and method to visualize forest fire flames and smoke through physical analysis in 3D virtual reality UE using the temperature and smoke results analyzed in WFDS.

WFDS was developed to analyze fire spread in open spaces adjacent to forests by applying topography and vegetation fuel by extending FDS developed for structural fire analysis.
The X-axis, Y-axis, and Z-axis were set to 200 m, 160 m, and 50 m, respectively, and the cell spacing was set to 2 m, resulting in a total of 200,000 cells were configured as 100 cells on the X-axis, 80 cells on the Y-axis, and 25 cells on the Z-axis.
For forest fuel, a combustion material, combustion properties were applied to Pinus densiflora with an average height of 17 m and 400 trees/ha, and Cone type was applied for the grid configuration.

Result values analyzed with WFDS are stored as Plot3Ddata files, velocity vectors, and physical quantities for fire analysis, and then extracted as vector files FGA files with a cycle of N(3~5) seconds so that they can be imported into 3D Unreal Engine.
The FGA file contains data values of vectors and physical quantities in the analysis result.
FGA file imported from 3D UE is created as a vector field, and Boundary values such as position, rotation, stile, intensity, and tightness are set.
With the generated vector field, the particles are completed by applying the fire and smoke effect used in VR 3D contents.
For visualization of forest fire diffusion and forest fuel combustion:
- For visualization of flames and smoke, FGA temperature and smoke (CO, CO2) concentration data are expressed through particle contrast and lighting effect functions.
- Image change due to forest fuel combustion used the Mesh Decal function as a visualization method with image values created according to the mass reduction rate.
- Mesh Decal uses the mixed function of semi-transparent Blend Mode and Deffered Decal by updating GBuffer and DBuffer after rendering 3D object surface geometry.
It was configured so that external results such as changes in heat flow of each grid value, wind speed, and wind direction in the UE can be reflected in the impact effect. This is useful for expressing the movement and concentration of smoke in each grid cell differently.

As a result of expressing the file extracted from the WFDS analysis result as an FGA file with the Unreal Engine, the vector and physical quantity data values such as heat and smoke of each 200,000 grid cells expressed 100% the same value without error even with time series changes.
For the visualization of the flame temperature and smoke values for the grid cell, the color and smoke concentration of the flame were adjusted and expressed through the particle contrast and lighting effect on the grid.
The accuracy of the visualization image for the flame intensity and smoke concentration was implemented so that it could be adjusted through the particle lighting function.
For the image change according to combustion of the 3D combustion material object data, the Mesh Deca technique was applied to create a material image, and then a method was used to replace the image by mass reduction rate.
Figure 4 shows the simulation results of forest fire spread in Unreal 3D engine using the forest fire diffusion formula of Alexandridis, Alex, et al. There were 2400 grids used for the terrain, and the prediction of wildfire volcanoes was expressed by applying the following conditions to each variable value such as wind, inclination, ambient temperature, and type of fuel material.
- Wind speed: $4.6$ m/s
- Wind direction: southwest wind
- Temperature: $32$ ℃, FMC (Fuel Moisture Contents): $6.3$ %
- Cell size: $5$ cm²

The SMV data and the UE visualization program grid value showed 100% agreement with respect to temperature and smoke, which are the calculation results of WFDS.
In the comparison of the displayed images of flame and smoke concentration, there was a difference in visual brightness and contrast.
The difference in the visual effect was developed to be similar to the SMV visualization data by adjusting the color and smoke concentration of the flame through each particle contrast and lighting effect of the 3D UE.
Through this study, a methodology for visualizing the accuracy of the properties of forest fires for realistic experience among various element technologies of forest fire education and training contents using virtual reality was presented.
Visualization studies that reflected real-time changing weather conditions were not yet reflected in the study.
In the future, the development of fire training contents in virtual space, including the development of educational and training evaluation scenarios, along with the results of this research, will be a more useful and safe learning tool for forest fire extinguishers.