Struct XpbdSolver 

pub struct XpbdSolver {
    pub num_substeps: usize,
    pub num_iterations: usize,
    pub sleep_threshold: Real,
    pub sleep_counter_max: usize,
    pub sleep_state: SleepState,
    /* private fields */
}

Extended Position Based Dynamics (XPBD) solver.

The solver performs the following pipeline per call to XpbdSolver::solve:

1. Predict positions using semi-implicit Euler integration.
2. For each sub-step, project all constraints.
3. Update velocities from corrected positions.
4. Apply velocity damping.

Fields

num_substeps: usize

Number of sub-steps per solver call.

num_iterations: usize

Number of constraint-projection iterations per sub-step.

sleep_threshold: Real

Velocity magnitude threshold below which a body is considered asleep.

sleep_counter_max: usize

Number of consecutive solver calls all particles must be below the sleep threshold before the body transitions to SleepState::Asleep.

sleep_state: SleepState

Current sleep state.

Implementations

impl XpbdSolver

pub fn new(num_substeps: usize) -> Self

Create a new XPBD solver with the given number of sub-steps.

pub fn with_iterations(num_substeps: usize, num_iterations: usize) -> Self

Create a solver with explicit sub-step and iteration counts.

pub fn wake(&mut self)

Wake the body up (reset sleep counter and state).

pub fn cfl_timestep( body: &SoftBody, dt_max: Real, max_displacement: Real, ) -> Real

Compute an adaptive CFL time-step given the current body state.

Returns the largest dt such that no particle moves more than max_displacement in one sub-step.

If all particles are static or have zero velocity, returns dt_max.

pub fn solve( &mut self, body: &mut SoftBody, constraints: &mut [Box<dyn SoftConstraint>], dt: Real, )

Run one full solve step over body with the given constraints.

pub fn integrate_positions(&self, body: &mut SoftBody, dt: Real)

Integrate particle positions forward by dt without constraint projection.

Useful when you want to call the integration and projection phases separately (e.g. from a higher-level PBD loop).

pub fn integrate_velocities(&self, body: &mut SoftBody, dt: Real)

Update particle velocities from the displacement since the last integrate_positions call (i.e. from prev_position).

Call this after all constraint projections for a sub-step.

pub fn apply_damping(&self, body: &mut SoftBody)

Apply velocity damping to all dynamic particles.

pub fn kinetic_energy(body: &SoftBody) -> Real

Compute total kinetic energy of the body (½ Σ mᵢ |vᵢ|²).

pub fn max_displacement(body: &SoftBody) -> Real

Compute the maximum particle displacement in the last sub-step.

Useful for adaptive iteration count decisions.

Trait Implementations

impl Clone for XpbdSolver

fn clone(&self) -> XpbdSolver

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for XpbdSolver

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

Formats the value using the given formatter.

impl Default for XpbdSolver

fn default() -> Self

Returns the “default value” for a type.