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fix regressions with sleeping behavior of kinematic bodies (#885)

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* fix kinematic bodies ignoring the wake_up flag when setting velocities

* fix: don’t allow kinematic bodies to fall asleep unless they velocities are at zero exactly.

* feat: add debug example for kinematic bodies sleep

* chore: update changelog

* chore: typo
This commit is contained in:
Sébastien Crozet
2025-10-17 12:22:23 +02:00
committed by GitHub
parent ae1d479857
commit 27b11b9d61
5 changed files with 129 additions and 18 deletions
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8
CHANGELOG.md
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@@ -1,3 +1,11 @@
## Unreleased
- Kinematic rigid-bodies will no longer fall asleep if they have a nonzero velocity, even if that velocity is very
small. The rationale is that, since that velocity is chosen by the user, they really want the platform to move even
if the speed is low.
- Fix bug where kinematic bodies would ignore the `wake_up` flag passed to `set_linear_velocity` and
`set_angular_velocity`.
## v0.30.0 (03 Oct. 2025)
- Update to parry 0.25 (which involves breaking changes in the `Voxels` API but improves its internal storage to support

5
examples3d/all_examples3.rs
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@@ -44,6 +44,7 @@ mod debug_cube_high_mass_ratio3;
mod debug_internal_edges3;
mod debug_long_chain3;
mod debug_multibody_ang_motor_pos3;
mod debug_sleeping_kinematic3;
mod gyroscopic3;
mod inverse_kinematics3;
mod joint_motor_position3;
@@ -132,6 +133,10 @@ pub fn main() {
"(Debug) shape modification",
debug_shape_modification3::init_world,
),
(
"(Debug) sleeping kinematics",
debug_sleeping_kinematic3::init_world,
),
("(Debug) deserialize", debug_deserialize3::init_world),
(
"(Debug) multibody ang. motor pos.",

88
examples3d/debug_sleeping_kinematic3.rs Normal file
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@@ -0,0 +1,88 @@
use rapier_testbed3d::Testbed;
use rapier3d::prelude::*;
pub fn init_world(testbed: &mut Testbed) {
/*
* World
*/
let mut bodies = RigidBodySet::new();
let mut colliders = ColliderSet::new();
let impulse_joints = ImpulseJointSet::new();
let multibody_joints = MultibodyJointSet::new();
/*
* Setup a velocity-based kinematic rigid body.
*/
let platform_body =
RigidBodyBuilder::kinematic_velocity_based().translation(vector![0.0, 1.5 + 0.8, 0.0]);
let platform_handle = bodies.insert(platform_body);
let collider = ColliderBuilder::cuboid(5.0, 0.5, 5.0);
colliders.insert_with_parent(collider, platform_handle, &mut bodies);
// A second velocity-based platform but this one will move super slow.
let slow_platform_body =
RigidBodyBuilder::kinematic_velocity_based().translation(vector![0.0, 0.0, 0.0]);
let slow_platform_handle = bodies.insert(slow_platform_body);
let collider = ColliderBuilder::cuboid(5.0, 0.5, 5.0);
colliders.insert_with_parent(collider, slow_platform_handle, &mut bodies);
/*
* Setup a callback to control the platform.
*/
let start_tick = 500;
let stop_tick = 1000;
testbed.add_callback(move |_, physics, _, run_state| {
if run_state.timestep_id == stop_tick {
println!("Both platforms should stop moving now and eventually fall asleep.");
// The platforms moved until this time. They must not be sleeping.
assert!(!physics.bodies[platform_handle].is_sleeping());
assert!(!physics.bodies[slow_platform_handle].is_sleeping());
if let Some(slow_platform) = physics.bodies.get_mut(slow_platform_handle) {
slow_platform.set_linvel(Vector::zeros(), true);
}
if let Some(platform) = physics.bodies.get_mut(platform_handle) {
platform.set_linvel(Vector::zeros(), true);
}
}
if run_state.timestep_id > stop_tick + 500 {
// Platforms should fall asleep shortly after we stopped moving them.
assert!(physics.bodies[platform_handle].is_sleeping());
assert!(physics.bodies[slow_platform_handle].is_sleeping());
}
if run_state.timestep_id < start_tick || run_state.timestep_id >= stop_tick {
return;
} else if run_state.timestep_id == start_tick {
println!("Platforms should start moving now and never stop.");
println!("The slow platform should move up and not sleep.");
// Platforms should have had plenty of time to fall asleep before we start moving them.
assert!(physics.bodies[platform_handle].is_sleeping());
assert!(physics.bodies[slow_platform_handle].is_sleeping());
let slow_velocity = vector![0.0, 0.01, 0.0];
if let Some(slow_platform) = physics.bodies.get_mut(slow_platform_handle) {
slow_platform.set_linvel(slow_velocity, true);
}
}
let velocity = vector![
0.0,
(run_state.time * 2.0).cos(),
run_state.time.sin() * 2.0
];
// Update the velocity-based kinematic body by setting its velocity.
if let Some(platform) = physics.bodies.get_mut(platform_handle) {
platform.set_linvel(velocity, true);
}
});
/*
* Run the simulation.
*/
testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
testbed.look_at(point![-10.0, 5.0, -10.0], Point::origin());
}

31
src/dynamics/island_manager.rs
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@@ -159,7 +159,14 @@ impl IslandManager {
let sq_linvel = rb.vels.linvel.norm_squared();
let sq_angvel = rb.vels.angvel.gdot(rb.vels.angvel);
update_energy(length_unit, &mut rb.activation, sq_linvel, sq_angvel, dt);
update_energy(
&mut rb.activation,
rb.body_type,
length_unit,
sq_linvel,
sq_angvel,
dt,
);
if rb.activation.time_since_can_sleep >= rb.activation.time_until_sleep {
// Mark them as sleeping for now. This will
@@ -291,16 +298,28 @@ impl IslandManager {
}
fn update_energy(
length_unit: Real,
activation: &mut RigidBodyActivation,
body_type: RigidBodyType,
length_unit: Real,
sq_linvel: Real,
sq_angvel: Real,
dt: Real,
) {
let linear_threshold = activation.normalized_linear_threshold * length_unit;
if sq_linvel < linear_threshold * linear_threshold.abs()
&& sq_angvel < activation.angular_threshold * activation.angular_threshold.abs()
{
let can_sleep = match body_type {
RigidBodyType::Dynamic => {
let linear_threshold = activation.normalized_linear_threshold * length_unit;
sq_linvel < linear_threshold * linear_threshold.abs()
&& sq_angvel < activation.angular_threshold * activation.angular_threshold.abs()
}
RigidBodyType::KinematicPositionBased | RigidBodyType::KinematicVelocityBased => {
// Platforms only sleep if both velocities are exactly zero. If it’s not exactly
// zero, then the user really wants them to move.
sq_linvel == 0.0 && sq_angvel == 0.0
}
RigidBodyType::Fixed => true,
};
if can_sleep {
activation.time_since_can_sleep += dt;
} else {
activation.time_since_can_sleep = 0.0;

15
src/dynamics/rigid_body.rs
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@@ -769,15 +769,12 @@ impl RigidBody {
pub fn set_linvel(&mut self, linvel: Vector<Real>, wake_up: bool) {
if self.vels.linvel != linvel {
match self.body_type {
RigidBodyType::Dynamic => {
RigidBodyType::Dynamic | RigidBodyType::KinematicVelocityBased => {
self.vels.linvel = linvel;
if wake_up {
self.wake_up(true)
}
}
RigidBodyType::KinematicVelocityBased => {
self.vels.linvel = linvel;
}
RigidBodyType::Fixed | RigidBodyType::KinematicPositionBased => {}
}
}
@@ -791,15 +788,12 @@ impl RigidBody {
pub fn set_angvel(&mut self, angvel: Real, wake_up: bool) {
if self.vels.angvel != angvel {
match self.body_type {
RigidBodyType::Dynamic => {
RigidBodyType::Dynamic | RigidBodyType::KinematicVelocityBased => {
self.vels.angvel = angvel;
if wake_up {
self.wake_up(true)
}
}
RigidBodyType::KinematicVelocityBased => {
self.vels.angvel = angvel;
}
RigidBodyType::Fixed | RigidBodyType::KinematicPositionBased => {}
}
}
@@ -813,15 +807,12 @@ impl RigidBody {
pub fn set_angvel(&mut self, angvel: Vector<Real>, wake_up: bool) {
if self.vels.angvel != angvel {
match self.body_type {
RigidBodyType::Dynamic => {
RigidBodyType::Dynamic | RigidBodyType::KinematicVelocityBased => {
self.vels.angvel = angvel;
if wake_up {
self.wake_up(true)
}
}
RigidBodyType::KinematicVelocityBased => {
self.vels.angvel = angvel;
}
RigidBodyType::Fixed | RigidBodyType::KinematicPositionBased => {}
}
}