Spotlight
December 2, 2025
CORYS reimagines railway simulation with Unreal Engine 5
When French simulation leader CORYS set out to modernize its entire production pipeline, the goal wasn’t simply to improve visuals—it was to transform how railway simulators are designed, built, and used.
With Unreal Engine 5 at the heart of its new ecosystem, CORYS can now simulate massive railway networks spanning multiple countries in a single unified world.
Few simulation companies are as storied as CORYS. With a pedigree stretching back to the early 1990s, the company was the first to bring 3D graphics to transportation simulation in 1991—well before the era of modern real-time engines.
Today, there are over 3,700 CORYS simulators in more than 60 countries, across sectors where precision and reliability are non-negotiable— transportation, power generation, and process industries.
Where failure isn’t an option, realism and accuracy must be absolute. “That's the standard we live by,” says Renaud Perez, VP - Transportation/Mobility Simulation Business Unit at CORYS. “When reality can't afford mistakes, our simulations must be perfect.”
With Unreal Engine 5 at the heart of its new ecosystem, CORYS can now simulate massive railway networks spanning multiple countries in a single unified world.
An earlier pioneer of 3D graphics in railway simulation
Few simulation companies are as storied as CORYS. With a pedigree stretching back to the early 1990s, the company was the first to bring 3D graphics to transportation simulation in 1991—well before the era of modern real-time engines.
Today, there are over 3,700 CORYS simulators in more than 60 countries, across sectors where precision and reliability are non-negotiable— transportation, power generation, and process industries.
Where failure isn’t an option, realism and accuracy must be absolute. “That's the standard we live by,” says Renaud Perez, VP - Transportation/Mobility Simulation Business Unit at CORYS. “When reality can't afford mistakes, our simulations must be perfect.”
VENUS: the foundation for a Europe-wide railway digital twin
Nothing embodies this commitment to precision and realism more than CORYS’ flagship UE5 project, VENUS. “It's a technical marvel,” says Renaud. “VENUS was our first Unreal Engine project and represents a major step toward a unified European railway simulator in a common simulated world.”
The complexity of the platform is staggering. VENUS simulates real-world railway networks across three European countries—Germany, Belgium, and the Netherlands—in a single 3D environment.
It supports cross-border operations, complete with each country’s unique signaling systems. Drivers and engineers can use the simulator to train, certify, and validate operations across hundreds of kilometers of virtual track.
And that’s just the beginning.
CORYS envisions the system as the foundation for a comprehensive European railway digital twin—one in which operators can seamlessly plan and train for operations across borders, accelerating the integration of European rail networks.
The company is also applying these same principles to light rail systems, like the newly released LRV simulator platform, which introduces new traffic and passenger AI systems.
“These new simulators are particularly significant, because they’re paving the way for what we call a ‘true digital twin’—combining high-resolution real-world data with photorealism on top of our ultra-accurate simulation platform,” says Renaud Perez.
Courtesy of CORYS
From technical debt to a fresh start
In 2022, CORYS embarked on what they refer to as their “Great Migration”: a full transition to Unreal Engine 5. Their legacy pipeline—built on legacy middleware and a suite of separate proprietary tools—had evolved into a patchwork of editors for track layout, signal logic, traffic systems, and 3D content.
Each tool had to export and reimport data, creating bottlenecks and version mismatches. The move to UE5 consolidated everything into one unified platform: 3D content creation, simulation logic, validation, and testing.
“We weren’t just changing graphics engines—we were preserving three decades of validated railway physics and simulation code while revolutionizing how we create and maintain simulators,” says Renaud. “It was about tackling 30 years of technical debt.”
Critically, CORYS adopted a plugin-based approach, avoiding modifications to Unreal Engine source code and enabling them to provide the latest UE features to customers.
Renaud says the impact on day-to-day work has been transformative.
Courtesy of CORYS
Artists, engineers, and instructors now collaborate in the same environment—no more exporting between tools, no more version conflicts, no more "well, it worked on my machine" scenarios.
The platform’s built-in world manager tool enables distributed teams to work on the same route simultaneously, with a cell-based checkout system that prevents conflicts while maintaining productivity.
3D content is immediately visible and functional in the simulation environment. Engineers see their work come to life instantly, cutting validation cycles from days to hours and dramatically improving the team’s CI/CD pipeline.
And changes that once consumed entire afternoons now happen in real time. The team can place a signal, validate its interlocking logic, verify driver sightlines, and test approach speeds—all without leaving the editor or recompiling.
The platform’s built-in world manager tool enables distributed teams to work on the same route simultaneously, with a cell-based checkout system that prevents conflicts while maintaining productivity.
3D content is immediately visible and functional in the simulation environment. Engineers see their work come to life instantly, cutting validation cycles from days to hours and dramatically improving the team’s CI/CD pipeline.
And changes that once consumed entire afternoons now happen in real time. The team can place a signal, validate its interlocking logic, verify driver sightlines, and test approach speeds—all without leaving the editor or recompiling.
Courtesy of CORYS
Reducing memory usage by up to 80% with HLODs
To manage worlds spanning up to 2,000 km with over 1.4 million objects, CORYS needs to leverage UE5's most powerful features.
“World Partition was game-changing for us,” says Renaud Perez. “We built our world manager on top of it, adding Google Maps-like functionality. It divides our worlds into one-square-kilometer cells, each containing multiple Data Layers.”
This cell-based architecture allows for automatic streaming based on user proximity and enables multiple collaborators to work in different sections at once.
Working with an environment this size means dealing with hundreds of thousands of high-polygon assets. Nanite’s cluster-based LOD system enables the team to use film-quality assets without manual optimization.
“Nanite is revolutionary for our use case,” says Renaud. “Railway environments contain massive amounts of high-polygon geometry—intricate track infrastructure, detailed buildings, complex catenary systems. Nanite’s cluster-based LOD system eliminated the need for manual LOD creation, which could have consumed weeks of artist time for each major asset.”
Courtesy of CORYS
By leveraging Hierarchical Levels of Detail (HLODs), the team can automatically generate proxy meshes for distant content, collapsing thousands of objects into single meshes, reducing draw calls by orders of magnitude, and memory usage by 50-80% for distant geometry.
The team also relies on Lumen to provide hardware ray-traced global illumination for photorealistic rendering. “When you’re training drivers who need to recognize specific signs, signals, and environmental conditions, lighting accuracy isn’t just aesthetic—it’s safety-critical,” says Renaud.
“What’s remarkable is how these systems work together multiplicatively,” says Renaud. “HLODs complement Nanite for extreme distances. World Partition provides the spatial structure. Data Layers add semantic organization. Together, they enable us to build virtual worlds that would have been impossible just a few years ago.”
The team also relies on Lumen to provide hardware ray-traced global illumination for photorealistic rendering. “When you’re training drivers who need to recognize specific signs, signals, and environmental conditions, lighting accuracy isn’t just aesthetic—it’s safety-critical,” says Renaud.
“What’s remarkable is how these systems work together multiplicatively,” says Renaud. “HLODs complement Nanite for extreme distances. World Partition provides the spatial structure. Data Layers add semantic organization. Together, they enable us to build virtual worlds that would have been impossible just a few years ago.”
Courtesy of CORYS
Transforming the Unreal Editor into a simulation powerhouse
These workflow and performance improvements are undoubtedly impressive, but the truly game-changing outcome of CORYS’ migration is its suite of custom tools built as Unreal Engine plugins. These effectively transform the Unreal Editor into a specialized ecosystem for railway simulation.
As well as the previously mentioned world manager, CORYS developed a custom terrain module that ensures precision near track corridors and applies automatic terrain adjustments during object placement.
Their bespoke procedural generation system dynamically generates railway infrastructure including tracks, catenaries, and platforms along trajectory curves, updating automatically when those curves change.
Courtesy of CORYS
The team built specialized editors to adjust and manipulate rail track and road networks, signal logic, and safety-critical systems.
And then there’s the high-resolution process integration.
“This is where it gets really exciting,” says Renaud. “We’ve integrated our unique acquisition and processing pipeline directly into Unreal.”
The team uses aerial orthophotos at up to 3 cm resolution, LiDAR scan data with 12 to 15 points per meter squared, and AI-powered reconstruction algorithms.
“This produces LOD 3.3 geometry with over 90% texture matching,” says Renaud. “When you do a virtual walkthrough, you feel like you’re truly in the real world.”
By integrating all of this inside Unreal Engine, CORYS achieved near-complete automation for repetitive production steps—turning multi-tool workflows that once took weeks into a single, real-time, visually validated process.
“The cumulative effect? We’ve transformed our production efficiency,” says Renaud. “What used to take multiple tools, countless export-import cycles, and weeks of iteration now happens in a single integrated environment with immediate visual feedback. Our team can focus on creating great content rather than fighting with tools.”
And then there’s the high-resolution process integration.
“This is where it gets really exciting,” says Renaud. “We’ve integrated our unique acquisition and processing pipeline directly into Unreal.”
The team uses aerial orthophotos at up to 3 cm resolution, LiDAR scan data with 12 to 15 points per meter squared, and AI-powered reconstruction algorithms.
“This produces LOD 3.3 geometry with over 90% texture matching,” says Renaud. “When you do a virtual walkthrough, you feel like you’re truly in the real world.”
By integrating all of this inside Unreal Engine, CORYS achieved near-complete automation for repetitive production steps—turning multi-tool workflows that once took weeks into a single, real-time, visually validated process.
“The cumulative effect? We’ve transformed our production efficiency,” says Renaud. “What used to take multiple tools, countless export-import cycles, and weeks of iteration now happens in a single integrated environment with immediate visual feedback. Our team can focus on creating great content rather than fighting with tools.”
Courtesy of CORYS
The road ahead: toward a unified digital twin for Europe
The scale and complexity of CORYS’ VENUS puts it among the most sophisticated railway simulation platforms in the world. Remarkably, the platform is just a stepping stone to something bigger, however.
“We’re moving from simulation as a training tool to simulation as a comprehensive digital twin platform,” says Renaud Perez. “The foundation we’ve built with Unreal Engine has opened paths toward integrating high-fidelity simulation with the entire operational lifecycle of railways.”
Next year, VENUS will evolve into a bona fide digital twin, combining the existing photorealistic, high-accuracy simulation with real-time operational data, asset management, and engineering workflows. Operators will use a single platform for training, route planning, infrastructure management, incident analysis, and system validation.
Then comes autonomous systems validation: as railways move toward automation, synthetic sensor data from simulators will be critical for training and validating AI systems. VENUS will be used to generate edge cases, dangerous scenarios, and rare conditions that would be difficult or impossible to capture in real-world testing.
“Beyond driver training, our simulators become tools for infrastructure planning, operational optimization, and safety analysis,” says Renaud. “Want to test how a new signaling configuration performs? Model it in the digital twin before deployment.”
Courtesy of CORYS
Reimagining what’s possible in railway simulation
CORYS has turned decades of legacy technology into a cutting-edge, real-time simulation platform that rivals the best in any industry.
By fully integrating its workflow within Unreal Engine 5, the company has not only transformed how railway simulators are built, but pushed the boundaries of what a railway simulator can be further than anyone thought possible.
“In just three years, we’ve transformed our technology and organization,” says Renaud. “The following three years will transform what’s possible in railway simulation and digital twin technology. We’re incredibly excited about what comes next.”