FrictionSim class

A friction-based simulation that decelerates exponentially.

Models scroll flings, swipe releases, and any motion that slows down due to air resistance or surface friction.

Position formula: x(t) = x₀ + v₀ · (drag^t - 1) / ln(drag)

Usage:

final sim = FrictionSim(position0: 0.0, velocity0: 500.0);
final pos = sim.position(0.3); // position at t=0.3 seconds
Inheritance

Constructors

FrictionSim({required double position0, required double velocity0, double drag = 0.135, double restVelocityThreshold = 1.0})

Properties

drag → double
Drag coefficient 0.0, 1.0. Lower = more friction, faster stop. Default 0.135 (matches Flutter's BouncingScrollPhysics).
final
hashCode → int
The hash code for this object.
no setterinherited
id → String
Unique identifier for this simulator type.
no setteroverride
position0 → double
Initial position.
final
restVelocityThreshold → double
Rest velocity threshold below which motion is considered stopped.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
stopTime → double
Estimated stop time (when velocity < threshold).
no setter
totalDistance → double
Total distance traveled until rest.
no setter
velocity0 → double
Initial velocity (units/sec).
final

Methods

isDone(double t) → bool
True when the simulation has effectively come to rest.
override
normalized(double t, {required double from, required double to}) → double
Normalizes position to 0.0, 1.0 based on from and to. Useful for driving AnimationController.value.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
position(double t) → double
Position at time t (seconds).
override
sample({double durationSec = 2.0, int sampleHz = 60}) → List<double>
Samples the simulation at sampleHz for durationSec seconds.
inherited
settleDuration({double maxTime = 10.0, int resolution = 120}) → double
Returns the time (seconds) at which isDone first becomes true, sampled at resolution steps per second. Returns maxTime if never done.
inherited
toString() → String
A string representation of this object.
override
velocity(double t) → double
Velocity at time t (units/second).
override

Operators

operator ==(Object other) → bool
The equality operator.
inherited

Static Methods

android({required double velocity0}) → FrictionSim
Android-like scroll physics.
heavy({required double velocity0}) → FrictionSim
Heavy surface — quick stop.
ios({required double velocity0}) → FrictionSim
iOS scroll physics drag coefficient.