INPUT 01
Rig mass
The powered vehicle, recursively connected implements, trailers, and payload are treated as one system.
Physics EngineeringFS25 LuaPrivate Beta
Ground Resistance
A lightweight vehicle-physics system that makes the ground, the machine, and the job matter.
Built for Farming Simulator 25, the project turns connected rig mass, implement demand, soil moisture, gradient, available power, and wheel slip into believable resistance—without custom terrain deformation or a heavy rendering system.
6+
Physics inputs
10 Hz
Fixed evaluation
0
Custom particles
Server
Physics authority
The engineering question
When should a tractor slow down—and when should it stop moving altogether?
Raw drag is not enough. A heavy tractor can still fail if its tyres cannot transmit power into wet soil; a small tractor can be overwhelmed by an implement even on dry ground; and a stationary vehicle should not magically regain traction while digging the same rut. Ground Resistance models these as related but distinct states: demand, strain, slip, physical bogging, and recovery.
// simplified signal path
rig + implement + terrain
↓
resistance + power demand
↓
slip + loss of progress
↓
persistent bog + traction loss
The model
Inputs with physical consequences
INPUT 02
Implement demand
Working width, operation type, lowered state, rated draft, and PTO demand contribute different forms of load.
INPUT 03
Terrain state
Field state, live rain, and optional position-aware soil moisture alter resistance and available traction.
INPUT 04
Power & grade
Available engine power and directional slope determine whether a rig can sustain the requested work.
INPUT 05
Wheel slip
Measured longitudinal slip separates ordinary engine strain from a genuine loss of ground traction.
INPUT 06
Bog memory
Sustained slip with little progress accumulates a persistent state, preventing unrealistic instant recovery.
Development method
Instrument, test, tune, repeat
An in-game diagnostic HUD exposes calculated rig mass, ground state, speed, throttle, grade, wetness, draft, PTO demand, strain, bog state, wheel slip, and experimental settlement. Each physics change is tested against a controlled comparison rather than tuned by feel alone.
Rig 23.9 t | Wet 100% | Draft 14.7 kN | Strain 100% | Bog 86% | Slip 74%1
Road → field
Baseline rolling resistance and surface transition
2
Tool raised → lowered
Mass load versus soil-working draft
3
Dry → wet
Resistance, traction loss, and bog accumulation
4
Small → large tractor
Power-to-demand mismatch and believable failure
5
Empty → loaded trailer
Recursive payload mass and drawbar demand
6
Player → multiplayer
Server-authoritative state and repeatable results
In-action media coming next
Controlled physics comparisons
Short captures will show the same implement behind mismatched tractors, dry versus rain-soaked soil, wheelspin under load, and recovery after raising the tool or reversing onto firm ground.
Design constraints
Built to coexist
Lightweight by design
No custom mud particles, texture layers, map deformation, or whole-map scans. Physics is evaluated at a fixed interval and fails safely when a vehicle does not expose an expected API.
Compatibility first
Dynamic Drive Pro can retain steering ownership, while Moisture System can optionally provide richer position-aware soil data without becoming a required dependency.
Multiplayer authority
The server decides physical state. Clients may display diagnostics, but do not independently apply resistance or traction changes that could diverge between players.
Measured iteration
Stable multiplayer checkpoints are separated from rapid single-player Beta builds, with synchronized version markers and reproducible package checksums.
Current status: private testing
The core model is working in single-player and has entered controlled two-player multiplayer testing. Public downloads will follow only after physics tuning and synchronization are proven stable.