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use na::{self, Real};

/// Parameters for a time-step of the physics engine.
pub struct IntegrationParameters<N: Real> {
    /// The timestep (default: `1.0 / 60.0`)
    pub dt: N,
    /// The Error Reduction Parameter in `[0, 1]` is the proportion of
    /// the positional error to be corrected at each time step (default: `0.2`).
    pub erp: N,
    /// Each cached impulse are multiplied by this coefficient in `[0, 1]`
    /// when they are re-used to initialize the solver (default `1.0`).
    pub warmstart_coeff: N,
    /// Contacts at points where the involved bodies have a relative
    /// velocity smaller than this threshold wont be affected by the restitution force (default: `1.0`).
    pub restitution_velocity_threshold: N,
    /// Ammount of penetration the engine wont attempt to correct (default: `0.001m`).
    pub allowed_linear_error: N,
    /// Ammount of angular drift of joint limits the engine wont
    /// attempt to correct (default: `0.001rad`).
    pub allowed_angular_error: N,
    /// Maximum linear correction during one step of the non-linear position solver (default: `100.0`).
    pub max_linear_correction: N,
    /// Maximum angular correction during one step of the non-linear position solver (default: `0.2`).
    pub max_angular_correction: N,
    /// Maximum nonlinera SOR-prox scaling parameter when the constraint
    /// correction direction is close to the kernel of the involved multibody's
    /// jacobian (default: `0.2`).
    pub max_stabilization_multiplier: N,
    /// Maximum number of iterations performed by the velocity constraints solver.
    pub max_velocity_iterations: usize,
    /// Maximum number of iterations performed by the position-based constraints solver.
    pub max_position_iterations: usize,
}

impl<N: Real> IntegrationParameters<N> {
    /// Creates a set of integration parameters with the given values.
    pub fn new(
        dt: N,
        erp: N,
        warmstart_coeff: N,
        restitution_velocity_threshold: N,
        allowed_linear_error: N,
        allowed_angular_error: N,
        max_linear_correction: N,
        max_angular_correction: N,
        max_stabilization_multiplier: N,
        max_velocity_iterations: usize,
        max_position_iterations: usize,
    ) -> Self {
        IntegrationParameters {
            dt,
            erp,
            warmstart_coeff,
            restitution_velocity_threshold,
            allowed_linear_error,
            allowed_angular_error,
            max_linear_correction,
            max_angular_correction,
            max_stabilization_multiplier,
            max_velocity_iterations,
            max_position_iterations,
        }
    }
}

impl<N: Real> Default for IntegrationParameters<N> {
    fn default() -> Self {
        Self::new(
            na::convert(1.0 / 60.0),
            na::convert(0.2),
            na::convert(1.0),
            na::convert(1.0),
            na::convert(0.001),
            na::convert(0.001),
            na::convert(100.0),
            na::convert(0.2),
            na::convert(0.2),
            8,
            3,
        )
    }
}