Arma 3 Vehicle PhysX Tuning Tool Workflow

This page explains how to use the RKSL Arma 3 Vehicle PhysX Tuning Tool to create a first-pass config.cpp and model.cfg export for simulation = “carx” and simulation = “tankx” vehicles.

The tool is here:

• RKSL Arma 3 Vehicle PhysX Tuning Tool

Use the tool as a structured data-entry and export aid. It does not replace in-game testing. Final values still need validation in Arma 3 using the actual P3D, memory points, geometry LOD, wheel selections, engine sound setup, and addon inheritance.

Before opening the tool, collect as much of this source material as possible.

The tool assumes Arma model-space style measurements:

• Longitudinal Y is vehicle length.
• Positive Y is forward.
• Negative Y is rearward.
• Track width is measured left wheel centre to right wheel centre.
• Axle station Y is measured relative to the vehicle centre or model origin used by the project.
• Wheel radius is measured from wheel centre to tyre tread.
• Wheel width is measured across the tyre.

The generated wheel classes use two wheels per axle:

The editable wheel base names drive these exported names:

Open the tool and select the simulation branch first.

For TankX layouts, keep all left-side wheels in one line, all right-side wheels in one line, and use the same wheel size across the driven ground-contact wheels. Add only wheels that meaningfully contact the ground. Sprockets and idlers do not need to be simulated unless they affect ground contact; if they are included and should not suspend, set maxCompression and maxDroop to 0.

Use the Arma 3 Config Viewer or source config to find a close parent vehicle. Prefer a known project base class over inheriting directly from a vanilla class if the addon already has shared vehicle base classes.

The generated model.cfg creates CfgSkeletons and CfgModels scaffolding for damper, steering, and wheel rotation animations. The exported names must match real named selections and memory axes in the P3D.

For a quick first pass, use real vehicle dimensions and leave measured layout off. For a serious export, enable measured layout and enter every axle station from the model.

Enable use measured layout when the model has known axle positions.

Measure each axle station from the model centre:

1. In Object Builder, identify the wheel centre or wheel axis memory point for the axle.
2. Read or measure its Y position.
3. Enter positive values for axles forward of centre.
4. Enter negative values for axles rearward of centre.
5. Measure track width from left wheel centre to right wheel centre for the same axle.

The preview mockup scales from these measured stations and tracks, so unusual layouts should be checked here before moving to wheel names.

The tool derives:

wheelCircumference = 2 * pi * wheelRadiusM
wheelMOI = 0.5 * wheelMassKg * wheelRadiusM^2

The MOI formula is a practical solid-cylinder approximation for a first pass. Tune MOI and wheel damping in game, especially for TankX vehicles where wheel MOI and damping have a large effect on acceleration, braking, and maximum speed.

Enter the wheel base name for each active wheel. The base name should match the project's P3D naming convention.

Example for axle 1:

For each base name, confirm these exist in the P3D:

• A rotating wheel selection or bone.
• A centre memory point.
• A boundary memory point.
• A damper selection/bone if using damper bone names.
• A damper axis for model.cfg if the damper animation is exported.
• A steering selection and steering axis for steerable CarX axles.

Use templates to adapt the export to the real model naming convention.

{base} is replaced with the wheel base name. If a model uses shared axes, enter the shared axis name without {base}.

The generated model.cfg animation stack per wheel is:

1. Damper translation using source damper.
2. Steering yaw using source steering, only on axles listed as steering axles.
3. Wheel rotation using source wheel for CarX.
4. Wheel rotation using wheelL or wheelR for TankX.

Use comma lists or ranges, for example:

1
1,2
1-3
2,4-6

For TankX, wheel steering should normally stay off. Use TankX turning fields in Step 8 instead.

The tool estimates load per axle from mass, axle positions, and CG Y offset. The sum of generated wheel sprungMass values should equal the vehicle mass.

For each axle:

springStrength = naturalFrequency^2 * sprungMass
springDamperRate = dampingRatio * 2 * sqrt(springStrength * sprungMass)

Start with matching left/right values on the same axle. Then tune in game for pitch, roll, bottoming out, braking dive, and obstacle response.

Treat tyre stiffness as a tuning pass, not a data-entry pass. Use a similar Arma 3 vehicle as a baseline, test on asphalt and off-road surfaces, and adjust only after mass, suspension, and wheel dimensions are credible.

The tool derives:

minOmega = idleRpm * 2 * pi / 60
maxOmega = redRpm * 2 * pi / 60

Use realistic RPM values if the vehicle has a real engine. If the vehicle is fictional, start from an existing Arma 3 vehicle with a similar mass and role.

The torque curve uses normalized engine speed on the X axis and a multiplier of peakTorque on the Y axis.

Example:

0.0, 0.55,
0.3, 0.85,
0.5, 1.0,
0.8, 0.92,
1.0, 0.72

Where to find it:

• Use a real dyno curve when available.
• If only peak torque and rated power are known, shape the curve from a similar engine.
• Keep the final curve smooth enough that gear changes do not drop the engine into an unusable RPM range.

Gearbox ratios should include exactly one reverse gear, one neutral gear, and forward gears ordered from higher ratio to lower ratio.

Example:

"R1", -3.231, "N", 0, "D1", 2.462, "D2", 1.870, "D3", 1.241, "D4", 0.970, "D5", 0.711

The tool estimates each forward gear speed:

finalRatio = gearRatio * finalDriveRatio
gearSpeedKmh = redRpm / finalRatio * wheelCircumference * 60 / 1000
wheelTorqueNm = peakTorqueNm * finalRatio

Use those derived speeds to check whether the gear stack matches the intended vehicle top speed and acceleration profile.

Use changeGearOmegaRatios[] when changeGearType is rpmratio. These are normalized RPM thresholds for automatic shifting.

Use changeGearMinEffectivity[] when changeGearType is effective. These values control shifting based on drivetrain effectivity.

Find starting values in a similar Arma 3 vehicle, then test:

• Launch from stationary.
• Full throttle acceleration.
• Hill starts.
• Low-speed reversing.
• Gear changes near top speed.
• AI driving.

Use real drivetrain layout when known. For example, an ordinary permanent 4×4 should not be tuned like a rear-wheel-drive car.

Tune handling aids after core mass, suspension, tyres, and gearbox are plausible. Do not use anti-roll or terrain coefficients to hide incorrect centre of mass or suspension values.

These fields appear only when TankX is selected.

A practical starting point for tankTurnForce is approximately:

tankTurnForce = vehicleMassKg * 11

Increase if the vehicle will not pivot or begin turning. Reduce if it spins too aggressively or breaks traction unrealistically.

Use this step to review checks and export files.

Always save the JSON profile with the addon source. It records assumptions, measured layout, editable wheel names, and tuning notes so the setup can be reproduced later.

After exporting, test in Arma 3 before considering the values final.

1. Confirm the vehicle spawns without config or model.cfg errors.
2. Confirm every wheel appears in the correct place and rotates around the correct axis.
3. Confirm damper animation moves in the correct direction.
4. Confirm steerable CarX wheels rotate visually and physically on the intended axles.
5. Confirm TankX left and right wheels rotate correctly and the vehicle can turn from rest.
6. Drive straight on flat road and check acceleration to target speed.
7. Brake from speed and check wheel lock, stopping distance, and vehicle pitch.
8. Drive across small obstacles and check bottoming out, wheel clipping, and suspension oscillation.
9. Test uphill starts and off-road movement.
10. Test AI driving on roads and rough terrain.
11. Damage wheels and confirm damaged/destroyed damping behaves acceptably.
12. Check multiplayer/server RPT logs if the vehicle is intended for MP.

• Bohemia Interactive Community: Arma 3 Vehicle Handling Configuration
• Bohemia Interactive Community: Arma 3 Cars Config Guidelines
• Bohemia Interactive Community: Arma 3 Tanks Config Guidelines
• Bohemia Interactive Community: CfgModels