nichkara/rapier
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

feat: make the constraints regularization coefficients configurable with angular frequency instead of explicit ERP

Browse Source
This commit is contained in:
Sébastien Crozet
2024-05-25 11:05:00 +02:00
committed by Sébastien Crozet
parent 62379de9ec
commit fdd935dbf1
8 changed files with 131 additions and 63 deletions
Download Patch File Download Diff File Expand all files Collapse all files

125
src/dynamics/integration_parameters.rs
View File

@@ -1,4 +1,5 @@
use crate::math::Real;
use na::RealField;
use std::num::NonZeroUsize;
// TODO: enabling the block solver in 3d introduces a lot of jitters in
@@ -9,9 +10,9 @@ pub(crate) static BLOCK_SOLVER_ENABLED: bool = cfg!(feature = "dim2");
#[derive(Copy, Clone, Debug)]
#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
pub struct IntegrationParameters {
/// The timestep length (default: `1.0 / 60.0`)
/// The timestep length (default: `1.0 / 60.0`).
pub dt: Real,
/// Minimum timestep size when using CCD with multiple substeps (default `1.0 / 60.0 / 100.0`)
/// Minimum timestep size when using CCD with multiple substeps (default: `1.0 / 60.0 / 100.0`).
///
/// When CCD with multiple substeps is enabled, the timestep is subdivided
/// into smaller pieces. This timestep subdivision won't generate timestep
@@ -23,20 +24,24 @@ pub struct IntegrationParameters {
/// to numerical instabilities.
pub min_ccd_dt: Real,
/// 0-1: multiplier for how much of the constraint violation (e.g. contact penetration)
/// will be compensated for during the velocity solve.
/// (default `0.1`).
pub erp: Real,
/// 0-1: the damping ratio used by the springs for Baumgarte constraints stabilization.
/// Lower values make the constraints more compliant (more "springy", allowing more visible penetrations
/// before stabilization).
/// (default `20.0`).
pub damping_ratio: Real,
/// > 0: the damping ratio used by the springs for contact constraint stabilization.
/// Lower values make the constraints more compliant (more "springy", allowing more visible
/// penetrations before stabilization).
/// (default `5.0`).
pub contact_damping_ratio: Real,
/// 0-1: multiplier for how much of the joint violation
/// will be compensated for during the velocity solve.
/// (default `1.0`).
pub joint_erp: Real,
/// > 0: the natural frequency used by the springs for contact constraint regularization.
/// Increasing this value will make it so that penetrations get fixed more quickly at the
/// expense of potential jitter effects due to overshooting. In order to make the simulation
/// look stiffer, it is recommended to increase the [`Self::damping_ratio`] instead of this
/// value.
/// (default: `30.0`).
pub contact_natural_frequency: Real,
/// > 0: the natural frequency used by the springs for joint constraint regularization.
/// Increasing this value will make it so that penetrations get fixed more quickly.
/// (default: `1.0e6`).
pub joint_natural_frequency: Real,
/// The fraction of critical damping applied to the joint for constraints regularization.
/// (default `1.0`).
@@ -45,7 +50,8 @@ pub struct IntegrationParameters {
/// The coefficient in `[0, 1]` applied to warmstart impulses, i.e., impulses that are used as the
/// initial solution (instead of 0) at the next simulation step.
///
/// This should generally be set to 1. Can be set to 0 if using a large [`Self::erp`] value.
/// This should generally be set to 1.
///
/// (default `1.0`).
pub warmstart_coefficient: Real,
@@ -53,7 +59,7 @@ pub struct IntegrationParameters {
///
/// This value is used internally to estimate some length-based tolerance. In particular, the
/// values [`IntegrationParameters::allowed_linear_error`],
/// [`IntegrationParameters::max_penetration_correction`],
/// [`IntegrationParameters::max_corrective_velocity`],
/// [`IntegrationParameters::prediction_distance`], [`RigidBodyActivation::linear_threshold`]
/// are scaled by this value implicitly.
///
@@ -71,7 +77,7 @@ pub struct IntegrationParameters {
/// Maximum amount of penetration the solver will attempt to resolve in one timestep.
///
/// This value is implicitly scaled by [`IntegrationParameters::length_unit`].
pub normalized_max_penetration_correction: Real,
pub normalized_max_corrective_velocity: Real,
/// The maximal distance separating two objects that will generate predictive contacts (default: `0.002m`).
///
/// This value is implicitly scaled by [`IntegrationParameters::length_unit`].
@@ -123,20 +129,53 @@ impl IntegrationParameters {
}
}
/// The ERP coefficient, multiplied by the inverse timestep length.
/// The contact’s spring angular frequency for constraints regularization.
pub fn angular_frequency(&self) -> Real {
self.contact_natural_frequency * Real::two_pi()
}
/// The [`Self::erp`] coefficient, multiplied by the inverse timestep length.
pub fn erp_inv_dt(&self) -> Real {
self.erp * self.inv_dt()
let ang_freq = self.angular_frequency();
ang_freq / (self.dt * ang_freq + 2.0 * self.contact_damping_ratio)
}
/// The joint ERP coefficient, multiplied by the inverse timestep length.
/// The effective Error Reduction Parameter applied for calculating regularization forces
/// on contacts.
///
/// This parameter is computed automatically from [`Self::natural_frequency`],
/// [`Self::damping_ratio`] and the substep length.
pub fn erp(&self) -> Real {
self.dt * self.erp_inv_dt()
}
/// The joint’s spring angular frequency for constraint regularization.
pub fn joint_angular_frequency(&self) -> Real {
self.joint_natural_frequency * Real::two_pi()
}
/// The [`Self::joint_erp`] coefficient, multiplied by the inverse timestep length.
pub fn joint_erp_inv_dt(&self) -> Real {
self.joint_erp * self.inv_dt()
let ang_freq = self.joint_angular_frequency();
ang_freq / (self.dt * ang_freq + 2.0 * self.joint_damping_ratio)
}
/// The CFM factor to be used in the constraints resolution.
/// The effective Error Reduction Parameter applied for calculating regularization forces
/// on joints.
///
/// This parameter is computed automatically from [`Self::joint_natural_frequency`],
/// [`Self::joint_damping_ratio`] and the substep length.
pub fn joint_erp(&self) -> Real {
self.dt * self.joint_erp_inv_dt()
}
/// The CFM factor to be used in the constraint resolution.
///
/// This parameter is computed automatically from [`Self::natural_frequency`],
/// [`Self::damping_ratio`] and the substep length.
pub fn cfm_factor(&self) -> Real {
// Compute CFM assuming a critically damped spring multiplied by the damping ratio.
let inv_erp_minus_one = 1.0 / self.erp - 1.0;
let inv_erp_minus_one = 1.0 / self.erp() - 1.0;
// let stiffness = 4.0 * damping_ratio * damping_ratio * projected_mass
// / (dt * dt * inv_erp_minus_one * inv_erp_minus_one);
@@ -145,7 +184,10 @@ impl IntegrationParameters {
// let cfm = 1.0 / (dt * dt * stiffness + dt * damping);
// NOTE: This simplifies to cfm = cfm_coeff / projected_mass:
let cfm_coeff = inv_erp_minus_one * inv_erp_minus_one
/ ((1.0 + inv_erp_minus_one) * 4.0 * self.damping_ratio * self.damping_ratio);
/ ((1.0 + inv_erp_minus_one)
* 4.0
* self.contact_damping_ratio
* self.contact_damping_ratio);
// Furthermore, we use this coefficient inside of the impulse resolution.
// Surprisingly, several simplifications happen there.
@@ -166,11 +208,14 @@ impl IntegrationParameters {
1.0 / (1.0 + cfm_coeff)
}
/// The CFM (constraints force mixing) coefficient applied to all joints for constraints regularization
/// The CFM (constraints force mixing) coefficient applied to all joints for constraints regularization.
///
/// This parameter is computed automatically from [`Self::joint_natural_frequency`],
/// [`Self::joint_damping_ratio`] and the substep length.
pub fn joint_cfm_coeff(&self) -> Real {
// Compute CFM assuming a critically damped spring multiplied by the damping ratio.
// The logic is similar to `Self::cfm_factor`.
let inv_erp_minus_one = 1.0 / self.joint_erp - 1.0;
let inv_erp_minus_one = 1.0 / self.joint_erp() - 1.0;
inv_erp_minus_one * inv_erp_minus_one
/ ((1.0 + inv_erp_minus_one)
* 4.0
@@ -186,11 +231,11 @@ impl IntegrationParameters {
/// Maximum amount of penetration the solver will attempt to resolve in one timestep.
///
/// This is equal to [`Self::normalized_max_penetration_correction`] multiplied by
/// This is equal to [`Self::normalized_max_corrective_velocity`] multiplied by
/// [`Self::length_unit`].
pub fn max_penetration_correction(&self) -> Real {
if self.normalized_max_penetration_correction != Real::MAX {
self.normalized_max_penetration_correction * self.length_unit
pub fn max_corrective_velocity(&self) -> Real {
if self.normalized_max_corrective_velocity != Real::MAX {
self.normalized_max_corrective_velocity * self.length_unit
} else {
Real::MAX
}
@@ -210,9 +255,9 @@ impl IntegrationParameters {
Self {
dt: 1.0 / 60.0,
min_ccd_dt: 1.0 / 60.0 / 100.0,
erp: 0.1,
damping_ratio: 20.0,
joint_erp: 1.0,
contact_natural_frequency: 30.0,
contact_damping_ratio: 5.0,
joint_natural_frequency: 1.0e6,
joint_damping_ratio: 1.0,
warmstart_coefficient: 1.0,
num_internal_pgs_iterations: 1,
@@ -226,7 +271,7 @@ impl IntegrationParameters {
// tons of islands, reducing SIMD parallelism opportunities.
min_island_size: 128,
normalized_allowed_linear_error: 0.001,
normalized_max_penetration_correction: Real::MAX,
normalized_max_corrective_velocity: 10.0,
normalized_prediction_distance: 0.002,
max_ccd_substeps: 1,
length_unit: 1.0,
@@ -240,8 +285,7 @@ impl IntegrationParameters {
/// warmstarting proves to be undesirable for your use-case.
pub fn tgs_soft_without_warmstart() -> Self {
Self {
erp: 0.6,
damping_ratio: 1.0,
contact_damping_ratio: 0.25,
warmstart_coefficient: 0.0,
num_additional_friction_iterations: 4,
..Self::tgs_soft()
@@ -253,12 +297,9 @@ impl IntegrationParameters {
/// This exists mainly for testing and comparison purpose.
pub fn pgs_legacy() -> Self {
Self {
erp: 0.8,
damping_ratio: 0.25,
warmstart_coefficient: 0.0,
num_additional_friction_iterations: 4,
num_solver_iterations: NonZeroUsize::new(1).unwrap(),
..Self::tgs_soft()
num_internal_pgs_iterations: 4,
..Self::tgs_soft_without_warmstart()
}
}
}