Let's talk about the player camera and the background behind it.
Every movement starts with the track geometry itself. The physically accurate curvature of both rails transfers forces to the wheelsets, then to the bogies, through the suspension system, and finally to the car body. Only after that are these movements additionally damped (smoothed) by the driver's seat and the player's viewpoint, creating the motion you experience from inside the cab.
The only thing you can adjust is the amplitude of the player's head movement if the motion feels too intense. The underlying physics simulation itself remains unchanged. Our goal was to recreate the feeling of riding a real train as closely as possible without causing discomfort or motion sickness.
Rails are the foundation of train movement. That's why, in Subtransit Drive, both rails participate in the physics simulation, and each wheelset interacts with them physically instead of simply following a predefined path. This allows the train to respond naturally to real obstacles – for example, rolling over small objects or, under certain conditions, derailing.
At the moment, derailments are intentionally restricted because the terrain does not yet have full collision support. Otherwise, an entire train could fall through the world, forcing the physics engine to simulate dozens of heavy bodies at once, resulting in a significant performance impact. There is also a multiplayer consideration: a derailed train would immediately disrupt gameplay for other drivers on the same server.
However, this is only an intermediate step. We plan to continue expanding the physics simulation so that the game world becomes a true engineering sandbox for experimentation. In the future, we aim to implement more advanced interactions between rolling stock and infrastructure, including a dynamic wheel-to-rail adhesion coefficient that changes depending on operating conditions, track conditions, and other factors.
A static adhesion coefficient is already used throughout the game and varies between different sections of the line. Below is an example where the coefficient was intentionally reduced to demonstrate wheel slip.
This philosophy extends throughout the entire project. Whenever possible, we prefer to let visual effects emerge naturally from the underlying simulation instead of faking them. As a result, many details that appear to be simple visual effects are actually direct consequences of the game's unified physics system.