I’m currently working on a train simulator prototype, and I’ve hit some frustrating design issues when it comes to simulating physics and train car movement. The scale I’m aiming for is comparable to games like Run8, SimRail, and Derail Valley. My main challenge lies in achieving realistic train physics that can handle up to 2000 individual train cars in a vast multiplayer environment while maintaining a believable experience for players.
I’ve set up some requirements that I think are crucial, like the need for realistic behavior in train couplers and the spring-damper mechanics. Each train car is treated as its own physics object, and there are some pretty high demands on performance since train speeds can go up to 250 km/h across large open worlds—think 100 to 200 km in size. Not to mention, I want support for both first and third-person camera views.
I’ve tried several approaches already. One involves using splines with custom physics. It’s been stable and friendly for multiplayer but handling collisions between cars and stabilizing coupling constraints has proven quite tricky. I also experimented with using physics joints as “spline travelers,” which seemed promising, but I struggle with braking mechanics and the fidelity of how real trains would behave under certain forces without them actually colliding.
Then there’s the full physics approach, where I tried using conical wheels on colliders that represent the rails. Although it feels great at low speeds, performance drastically drops as speeds increase, making it tough to manage CPU resources effectively and sync in multiplayer.
I’m wondering if anyone out there has experience or knowledge of hybrid approaches to train car movement simulation that can help improve stability without sacrificing realism, especially in the context of large-scale online environments. I’d love to hear about any techniques or methods that have worked for you in similar situations, especially if they cater to a robust gaming experience rather than a full research-grade physics engine. Any insights would be greatly appreciated!
Wow, that sounds like a super ambitious project! I totally get the struggle with simulating physics in something as complex as a train simulator. You might want to think about blending your current approaches a bit more. Since you’re dealing with so many train cars and high speeds, maybe consider a simplified physics model for the majority of the cars while keeping more detailed physics for the ones that are close to the player or in the spotlight.
For the couplers and spring-damper mechanics, have you thought about just applying forces and constraints at a higher level rather than for each individual car? This could help reduce the CPU load. You could also implement a system where the physics updates for train cars further away are less frequent, maybe every few frames, while closer ones get updated more often.
Regarding your collision issues, could you try using a prediction-based system for collisions? Instead of having every car fully simulate physical interactions, you could predict where they should be and only fully simulate the interactions when they get close enough to each other. It might help prevent the big drops in performance you’re seeing.
And about the camera views—you could also consider a fixed camera for multiplayer views that only switches to first-person or third-person when a player is in a certain area or interacts with a certain object. This could help prioritize performance where it matters most.
Hope this helps a bit! I’m excited to see how your prototype evolves, and I bet there are many people rooting for you!
A hybrid solution that balances realism and performance for large-scale multiplayer train simulations can involve integrating spline-based pathing with carefully tuned, simplified physics constraints. Using splines to manage the general movement direction and ensure multiplayer synchronization is a solid foundation, while layered physics constraints such as adjustable spring-damper joints can handle the dynamic interactions between cars. Instead of fully dynamic collisions at all times, these constraints could include threshold-based approximations for coupler tension and compression, activating more detailed physics only under significant force or speed-related events. Additionally, leveraging level-of-detail (LOD) physics by simulating closely grouped car clusters as rigid bodies under certain conditions could significantly optimize CPU load without sacrificing realism too noticeably.
Another effective approach involves adaptive physics simulations, selectively applying high-fidelity conical wheel-on-rail modeling only near player-controlled or closely-monitored train segments, while remote or inactive cars use simplified physics representations. By dynamically adjusting physics calculations based on proximity to players, speed thresholds, and coupling forces, you can maintain realism and stability without overwhelming performance. Furthermore, employing asynchronous, network-friendly interpolation methods can help smooth player experiences during transitions between varying physics complexities. Carefully balancing these techniques can yield a stable, realistic, and scalable multiplayer train simulator consistent with your ambitious goals.