Real-Time Thermodynamics and Humidity Simulation Under Time Scaling, Pause, and Reverse Time in Unreal Engine 5

This record contains the paper “Real-Time Thermodynamics and Humidity Simulation Under Time Scaling, Pause, and Reverse Time in Unreal Engine 5”, which presents a real-time thermodynamics-inspired model for simulating temperature, relative humidity, dew point, and related moisture states, designed to integrate cleanly into Unreal Engine 5. The paper focuses on numerical stability and determinism when the engine’s notion of time is manipulated: time scaling (speed-up/slow-down), pause, and reverse time. It documents the system’s invariants, update rules, and implementation considerations needed to prevent discontinuities, drift, and non-physical behavior during transitions and time-direction changes. It also includes a performance evaluation of the runtime cost per simulation update (recalculation event) across multiple scenarios (reported via percentiles), reflecting the fact that the model is not necessarily executed every engine tick and may run only when an update is due. The goal is to provide a reproducible foundation for building coherent climate simulation behavior in UE5, especially for projects where time may be compressed, frozen, or rewound.