Struct FrictionSimulation 

pub struct FrictionSimulation { /* private fields */ }

Friction deceleration — scroll and fling momentum — in closed form.

drag ∈ (0, 1): the closer to 1, the longer the motion keeps rolling.

Implementations

impl FrictionSimulation

pub fn new( drag: f32, position: f32, velocity: f32, tolerance: Tolerance, ) -> Self

Friction from position at velocity, with the coefficient drag.

pub fn with_constant_deceleration( drag: f32, position: f32, velocity: f32, tolerance: Tolerance, constant_deceleration: f32, ) -> Self

Friction with a constant deceleration on top of the drag.

constant_deceleration is given unsigned and applied against the direction of travel. Nought gives exactly Self::new; anything else brings the motion to a stop in finite time, which drag alone never does.

The closed forms stop working here. With drag alone, dx(t) = v₀·D^t is invertible and the instant the motion passes a given point can be written down; add −c·t and neither the stopping time nor the crossing time has a closed form at all. Both are found by Newton’s method, which is what the reference does and for the same reason.

pub fn through( start: f32, end: f32, start_velocity: f32, end_velocity: f32, tolerance: Tolerance, ) -> Self

A friction calibrated to pass through start (at start_velocity) and stop at end (at end_velocity), deriving drag from that. drag = e^((v₀ − v₁)/(x₀ − x₁)).

pub fn final_x(&self) -> f32

The final position — the limit as t → ∞, or the place the motion actually stops when a constant deceleration gives it an end.

pub fn time_at_x(&self, x: f32) -> f32

The instant at which the motion passes through x, or ∞ when it never does — because it starts the wrong way round, or because x lies beyond Self::final_x. Inverting x(t) is what lets a fling hand over to a spring exactly at the edge of the content.

Trait Implementations

impl Clone for FrictionSimulation

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for FrictionSimulation

impl Debug for FrictionSimulation

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Simulation for FrictionSimulation

fn x(&self, time: f32) -> f32

The position at instant time.

fn dx(&self, time: f32) -> f32

The velocity — the derivative of position — at instant time.

fn is_done(&self, time: f32) -> bool

true once the motion has finished, within the tolerances.

fn tolerance(&self) -> Tolerance

The stopping thresholds.