Class FrictionBase

Abstract base class for tire friction implementations in WheelController3D. Handles conversion of wheel slip conditions into tire forces that drive vehicle dynamics. Friction models translate slip velocities and tire loads into forces that affect vehicle movement.

Inheritance
object
Object
Component
Behaviour
MonoBehaviour
FrictionBase
StandardFriction
Namespace: NWH.WheelController3D
Assembly: NWH.WheelController.dll
Syntax
public abstract class FrictionBase : MonoBehaviour
Remarks

Friction implementations calculate longitudinal (forward/backward) and lateral (side-to-side) tire forces based on slip ratios, slip angles, normal load, and tire characteristics defined in FrictionPresets. The system provides StandardFriction as the default curve-based model.

Forces are calculated every physics frame and applied to the vehicle Rigidbody through WheelControllerManager to ensure proper force accumulation and application order.

Fields

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brokeStaticThisFrame

Set to true when static friction breaks this physics frame. Used by WheelControllerGroup to coordinate break across all wheels. Reset at the start of each UpdateFriction call.

Declaration
[NonSerialized]
public bool brokeStaticThisFrame
Field Value
Type Description
bool
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isStaticActive

Indicates whether the tire is currently in static friction mode (anchored).

Declaration
[NonSerialized]
public bool isStaticActive
Field Value
Type Description
bool
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staticReEntryCooldown

Frames remaining before static friction can re-engage after being broken.

Declaration
[NonSerialized]
public int staticReEntryCooldown
Field Value
Type Description
int

Methods

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BreakStaticFriction(int, bool)

Forces the tire to exit static friction mode. Called by WheelControllerGroup when coordinating static friction break across all wheels on a vehicle.

Declaration
public virtual void BreakStaticFriction(int cooldownFrames = 0, bool clearFilterHistory = false)
Parameters
Type Name Description
int cooldownFrames

Substeps to wait before re-entry. 0 = use the friction implementation's configured cooldown (StandardFriction.staticFrictionCooldownFrames).
bool clearFilterHistory

If true, also zero the relaxation-filter history so the next dynamic substep starts from a clean baseline. Use for external breaks (vehicle reset, teleport) where the prior _prev force values are no longer meaningful. Cascading breaks from CoordinateStaticFrictionBreak should keep the default (false) so the in-substep seeding done inside ProcessStaticFriction is preserved.
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UpdateFriction(WheelController, float)

Calculates and updates tire friction forces based on current wheel slip and load conditions. Called every physics frame (FixedUpdate) to determine longitudinal and lateral tire forces. Implementation should update wheel.angularVelocity, frictionForceMagnitude, frictionSlip, and frictionForce.

Declaration
public abstract void UpdateFriction(WheelController wc, float deltaTime)
Parameters
Type Name Description
WheelController wc

WheelController instance containing current state: slip data, load, speed, and tire properties
float deltaTime

Physics timestep duration in seconds (typically Time.fixedDeltaTime)
Remarks

The method should:

  1. Calculate longitudinal slip and forces (acceleration/braking)
  2. Update wheel.angularVelocity based on motor torque, brake torque, and friction
  3. Set wc.frictionForceMagnitude (X=longitudinal, Y=lateral) in Newtons
  4. Set wc.frictionSlip (X=longitudinal, Y=lateral) as normalized values
  5. Calculate wc.counterTorque for powertrain feedback

Access current state through:

  • wc.frictionSpeed: Contact point velocity (X=forward, Y=sideways)
  • wc.load: Current vertical tire load in Newtons
  • wc.loadRating: Maximum rated tire load
  • wc.activeFrictionPreset: Current friction curve parameters
  • wc.motorTorque/brakeTorque: Applied torques
  • wc.wheel.angularVelocity: Current wheel rotation speed