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Fix delta_time being 0 resulting in incorrect simulation #660

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6 changes: 6 additions & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
## Unreleased

### Fix

- Fix `NaN` values appearin in bodies translation and rotation after a simulation step with a delta time equal to 0 ([#660](https://github.com/dimforge/rapier/pull/660)).
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## v0.20.0 (9 June 2024)

This release introduces two new crates:
Expand Down
15 changes: 12 additions & 3 deletions src/dynamics/integration_parameters.rs
Original file line number Diff line number Diff line change
Expand Up @@ -181,7 +181,12 @@ impl IntegrationParameters {
/// [`Self::contact_damping_ratio`] and the substep length.
pub fn contact_cfm_factor(&self) -> Real {
// Compute CFM assuming a critically damped spring multiplied by the damping ratio.
let inv_erp_minus_one = 1.0 / self.contact_erp() - 1.0;
// The logic is similar to [`Self::joint_cfm_coeff`].
let contact_erp = self.contact_erp();
if contact_erp == 0.0 {
return 0.0;
}
let inv_erp_minus_one = 1.0 / contact_erp - 1.0;

// let stiffness = 4.0 * damping_ratio * damping_ratio * projected_mass
// / (dt * dt * inv_erp_minus_one * inv_erp_minus_one);
Expand Down Expand Up @@ -220,8 +225,12 @@ impl IntegrationParameters {
/// [`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;
// The logic is similar to `Self::contact_cfm_factor`.
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let joint_erp = self.joint_erp();
if joint_erp == 0.0 {
return 0.0;
}
let inv_erp_minus_one = 1.0 / joint_erp - 1.0;
inv_erp_minus_one * inv_erp_minus_one
/ ((1.0 + inv_erp_minus_one)
* 4.0
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2 changes: 1 addition & 1 deletion src/dynamics/rigid_body_set.rs
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ impl BodyPair {
}

#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
#[derive(Clone, Default)]
#[derive(Clone, Default, Debug)]
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/// A set of rigid bodies that can be handled by a physics pipeline.
pub struct RigidBodySet {
// NOTE: the pub(crate) are needed by the broad phase
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68 changes: 67 additions & 1 deletion src/pipeline/physics_pipeline.rs
Original file line number Diff line number Diff line change
Expand Up @@ -662,14 +662,16 @@ impl PhysicsPipeline {

#[cfg(test)]
mod test {
use na::point;

use crate::dynamics::{
CCDSolver, ImpulseJointSet, IntegrationParameters, IslandManager, RigidBodyBuilder,
RigidBodySet,
};
use crate::geometry::{BroadPhaseMultiSap, ColliderBuilder, ColliderSet, NarrowPhase};
use crate::math::Vector;
use crate::pipeline::PhysicsPipeline;
use crate::prelude::{MultibodyJointSet, RigidBodyType};
use crate::prelude::{MultibodyJointSet, RevoluteJointBuilder, RigidBodyType};

#[test]
fn kinematic_and_fixed_contact_crash() {
Expand Down Expand Up @@ -937,4 +939,68 @@ mod test {
// Expect body to now be in active_dynamic_set
assert!(islands.active_dynamic_set.contains(&h));
}

#[test]
fn joint_step_delta_time_0() {
let mut colliders = ColliderSet::new();
let mut impulse_joints = ImpulseJointSet::new();
let mut multibody_joints = MultibodyJointSet::new();
let mut pipeline = PhysicsPipeline::new();
let mut bf = BroadPhaseMultiSap::new();
let mut nf = NarrowPhase::new();
let mut islands = IslandManager::new();

let mut bodies = RigidBodySet::new();

// Initialize bodies
let rb = RigidBodyBuilder::fixed().additional_mass(1.0).build();
let h = bodies.insert(rb.clone());
let rb_dynamic = RigidBodyBuilder::dynamic().additional_mass(1.0).build();
let h_dynamic = bodies.insert(rb_dynamic.clone());

// Add joint
#[cfg(feature = "dim2")]
let joint = RevoluteJointBuilder::new()
.local_anchor1(point![0.0, 1.0].into())
.local_anchor2(point![0.0, -3.0].into());
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#[cfg(feature = "dim3")]
let joint = RevoluteJointBuilder::new(Vector::z_axis())
.local_anchor1(point![0.0, 1.0, 0.0].into())
.local_anchor2(point![0.0, -3.0, 0.0].into());
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impulse_joints.insert(h, h_dynamic, joint, true);

let mut parameters = IntegrationParameters::default();
parameters.dt = 0f32.into();
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// Step once
let gravity = Vector::y() * -9.81;
pipeline.step(
&gravity,
&parameters,
&mut islands,
&mut bf,
&mut nf,
&mut bodies,
&mut colliders,
&mut impulse_joints,
&mut multibody_joints,
&mut CCDSolver::new(),
None,
&(),
&(),
);
let translation = bodies.get(h_dynamic).unwrap().translation();
let rotation = bodies.get(h_dynamic).unwrap().rotation();
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assert!(translation.x.is_finite());
assert!(translation.y.is_finite());
#[cfg(feature = "dim2")]
assert!(rotation.is_finite());
#[cfg(feature = "dim3")]
{
assert!(translation.z.is_finite());
assert!(rotation.i.is_finite());
assert!(rotation.j.is_finite());
assert!(rotation.k.is_finite());
assert!(rotation.w.is_finite());
}
}
}