Merge pull request #183 from dimforge/bundles

Make Rapier accept any kind of data storage instead of RigidBodySet/ColliderSet

1 files changed, 811 insertions, 0 deletions

diff --git a/src/dynamics/rigid_body_components.rs b/src/dynamics/rigid_body_components.rs
new file mode 100644
index 0000000..2a652f7
--- /dev/null
+++ b/src/dynamics/rigid_body_components.rs
@@ -0,0 +1,811 @@
+use crate::data::{ComponentSetMut, ComponentSetOption};
+use crate::dynamics::MassProperties;
+use crate::geometry::{
+    ColliderChanges, ColliderHandle, ColliderMassProperties, ColliderParent, ColliderPosition,
+    ColliderShape, InteractionGraph, RigidBodyGraphIndex,
+};
+use crate::math::{AngVector, AngularInertia, Isometry, Point, Real, Translation, Vector};
+use crate::parry::partitioning::IndexedData;
+use crate::utils::{WCross, WDot};
+use num::Zero;
+
+/// The unique handle of a rigid body added to a `RigidBodySet`.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[repr(transparent)]
+pub struct RigidBodyHandle(pub crate::data::arena::Index);
+
+impl RigidBodyHandle {
+    /// Converts this handle into its (index, generation) components.
+    pub fn into_raw_parts(self) -> (u32, u32) {
+        self.0.into_raw_parts()
+    }
+
+    /// Reconstructs an handle from its (index, generation) components.
+    pub fn from_raw_parts(id: u32, generation: u32) -> Self {
+        Self(crate::data::arena::Index::from_raw_parts(id, generation))
+    }
+
+    /// An always-invalid rigid-body handle.
+    pub fn invalid() -> Self {
+        Self(crate::data::arena::Index::from_raw_parts(
+            crate::INVALID_U32,
+            crate::INVALID_U32,
+        ))
+    }
+}
+
+impl IndexedData for RigidBodyHandle {
+    fn default() -> Self {
+        Self(IndexedData::default())
+    }
+
+    fn index(&self) -> usize {
+        self.0.index()
+    }
+}
+
+/// The type of a body, governing the way it is affected by external forces.
+#[deprecated(note = "renamed as RigidBodyType")]
+pub type BodyStatus = RigidBodyType;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+/// The status of a body, governing the way it is affected by external forces.
+pub enum RigidBodyType {
+    /// A `RigidBodyType::Dynamic` body can be affected by all external forces.
+    Dynamic,
+    /// A `RigidBodyType::Static` body cannot be affected by external forces.
+    Static,
+    /// A `RigidBodyType::Kinematic` body cannot be affected by any external forces but can be controlled
+    /// by the user at the position level while keeping realistic one-way interaction with dynamic bodies.
+    ///
+    /// One-way interaction means that a kinematic body can push a dynamic body, but a kinematic body
+    /// cannot be pushed by anything. In other words, the trajectory of a kinematic body can only be
+    /// modified by the user and is independent from any contact or joint it is involved in.
+    Kinematic,
+    // Semikinematic, // A kinematic that performs automatic CCD with the static environment to avoid traversing it?
+    // Disabled,
+}
+
+impl RigidBodyType {
+    /// Is this rigid-body static (i.e. cannot move)?
+    pub fn is_static(self) -> bool {
+        self == RigidBodyType::Static
+    }
+
+    /// Is this rigid-body dynamic (i.e. can move and be affected by forces)?
+    pub fn is_dynamic(self) -> bool {
+        self == RigidBodyType::Dynamic
+    }
+
+    /// Is this rigid-body kinematic (i.e. can move but is unaffected by forces)?
+    pub fn is_kinematic(self) -> bool {
+        self == RigidBodyType::Kinematic
+    }
+}
+
+bitflags::bitflags! {
+    #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+    /// Flags describing how the rigid-body has been modified by the user.
+    pub struct RigidBodyChanges: u32 {
+        /// Flag indicating that any component of this rigid-body has been modified.
+        const MODIFIED    = 1 << 0;
+        /// Flag indicating that the `RigidBodyPosition` component of this rigid-body has been modified.
+        const POSITION    = 1 << 1;
+        /// Flag indicating that the `RigidBodyActivation` component of this rigid-body has been modified.
+        const SLEEP       = 1 << 2;
+        /// Flag indicating that the `RigidBodyColliders` component of this rigid-body has been modified.
+        const COLLIDERS   = 1 << 3;
+        /// Flag indicating that the `RigidBodyType` component of this rigid-body has been modified.
+        const TYPE        = 1 << 4;
+    }
+}
+
+impl Default for RigidBodyChanges {
+    fn default() -> Self {
+        RigidBodyChanges::empty()
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// The position of this rigid-body.
+pub struct RigidBodyPosition {
+    /// The world-space position of the rigid-body.
+    pub position: Isometry<Real>,
+    /// The next position of the rigid-body.
+    ///
+    /// At the beginning of the timestep, and when the
+    /// timestep is complete we must have position == next_position
+    /// except for kinematic bodies.
+    ///
+    /// The next_position is updated after the velocity and position
+    /// resolution. Then it is either validated (ie. we set position := set_position)
+    /// or clamped by CCD.
+    pub next_position: Isometry<Real>,
+}
+
+impl Default for RigidBodyPosition {
+    fn default() -> Self {
+        Self {
+            position: Isometry::identity(),
+            next_position: Isometry::identity(),
+        }
+    }
+}
+
+impl RigidBodyPosition {
+    /// Computes the velocity need to travel from `self.position` to `self.next_position` in
+    /// a time equal to `1.0 / inv_dt`.
+    #[must_use]
+    pub fn interpolate_velocity(&self, inv_dt: Real) -> RigidBodyVelocity {
+        let dpos = self.next_position * self.position.inverse();
+        let angvel;
+        #[cfg(feature = "dim2")]
+        {
+            angvel = dpos.rotation.angle() * inv_dt;
+        }
+        #[cfg(feature = "dim3")]
+        {
+            angvel = dpos.rotation.scaled_axis() * inv_dt;
+        }
+        let linvel = dpos.translation.vector * inv_dt;
+        RigidBodyVelocity { linvel, angvel }
+    }
+
+    /// Compute new positions after integrating the given forces and velocities.
+    ///
+    /// This uses a symplectic Euler integration scheme.
+    #[must_use]
+    pub fn integrate_forces_and_velocities(
+        &self,
+        dt: Real,
+        forces: &RigidBodyForces,
+        vels: &RigidBodyVelocity,
+        mprops: &RigidBodyMassProps,
+    ) -> Isometry<Real> {
+        let new_vels = forces.integrate(dt, vels, mprops);
+        new_vels.integrate(dt, &self.position, &mprops.mass_properties.local_com)
+    }
+}
+
+impl<T> From<T> for RigidBodyPosition
+where
+    Isometry<Real>: From<T>,
+{
+    fn from(position: T) -> Self {
+        let position = position.into();
+        Self {
+            position,
+            next_position: position,
+        }
+    }
+}
+
+bitflags::bitflags! {
+    #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+    /// Flags affecting the behavior of the constraints solver for a given contact manifold.
+    pub struct RigidBodyMassPropsFlags: u8 {
+        /// Flag indicating that the rigid-body cannot translate along any direction.
+        const TRANSLATION_LOCKED = 1 << 0;
+        /// Flag indicating that the rigid-body cannot rotate along the `X` axis.
+        const ROTATION_LOCKED_X = 1 << 1;
+        /// Flag indicating that the rigid-body cannot rotate along the `X` axis.
+        const ROTATION_LOCKED_Y = 1 << 2;
+        /// Flag indicating that the rigid-body cannot rotate along the `X` axis.
+        const ROTATION_LOCKED_Z = 1 << 3;
+        /// Combination of flags indicating that the rigid-body cannot rotate along any axis.
+        const ROTATION_LOCKED = Self::ROTATION_LOCKED_X.bits | Self::ROTATION_LOCKED_Y.bits | Self::ROTATION_LOCKED_Z.bits;
+    }
+}
+
+// TODO: split this into "LocalMassProps" and `WorldMassProps"?
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// The mass properties of this rigid-bodies.
+pub struct RigidBodyMassProps {
+    /// Flags for locking rotation and translation.
+    pub flags: RigidBodyMassPropsFlags,
+    /// The local mass properties of the rigid-body.
+    pub mass_properties: MassProperties,
+    /// The world-space center of mass of the rigid-body.
+    pub world_com: Point<Real>,
+    /// The inverse mass taking into account translation locking.
+    pub effective_inv_mass: Real,
+    /// The square-root of the world-space inverse angular inertia tensor of the rigid-body,
+    /// taking into account rotation locking.
+    pub effective_world_inv_inertia_sqrt: AngularInertia<Real>,
+}
+
+impl Default for RigidBodyMassProps {
+    fn default() -> Self {
+        Self {
+            flags: RigidBodyMassPropsFlags::empty(),
+            mass_properties: MassProperties::zero(),
+            world_com: Point::origin(),
+            effective_inv_mass: 0.0,
+            effective_world_inv_inertia_sqrt: AngularInertia::zero(),
+        }
+    }
+}
+
+impl From<RigidBodyMassPropsFlags> for RigidBodyMassProps {
+    fn from(flags: RigidBodyMassPropsFlags) -> Self {
+        Self {
+            flags,
+            ..Self::default()
+        }
+    }
+}
+
+impl RigidBodyMassProps {
+    /// The mass of the rigid-body.
+    #[must_use]
+    pub fn mass(&self) -> Real {
+        crate::utils::inv(self.mass_properties.inv_mass)
+    }
+
+    /// The effective mass (that takes the potential translation locking into account) of
+    /// this rigid-body.
+    #[must_use]
+    pub fn effective_mass(&self) -> Real {
+        crate::utils::inv(self.effective_inv_mass)
+    }
+
+    /// Update the world-space mass properties of `self`, taking into account the new position.
+    pub fn update_world_mass_properties(&mut self, position: &Isometry<Real>) {
+        self.world_com = self.mass_properties.world_com(&position);
+        self.effective_inv_mass = self.mass_properties.inv_mass;
+        self.effective_world_inv_inertia_sqrt = self
+            .mass_properties
+            .world_inv_inertia_sqrt(&position.rotation);
+
+        // Take into account translation/rotation locking.
+        if self
+            .flags
+            .contains(RigidBodyMassPropsFlags::TRANSLATION_LOCKED)
+        {
+            self.effective_inv_mass = 0.0;
+        }
+
+        #[cfg(feature = "dim2")]
+        {
+            if self
+                .flags
+                .contains(RigidBodyMassPropsFlags::ROTATION_LOCKED_Z)
+            {
+                self.effective_world_inv_inertia_sqrt = 0.0;
+            }
+        }
+        #[cfg(feature = "dim3")]
+        {
+            if self
+                .flags
+                .contains(RigidBodyMassPropsFlags::ROTATION_LOCKED_X)
+            {
+                self.effective_world_inv_inertia_sqrt.m11 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m12 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m13 = 0.0;
+            }
+
+            if self
+                .flags
+                .contains(RigidBodyMassPropsFlags::ROTATION_LOCKED_Y)
+            {
+                self.effective_world_inv_inertia_sqrt.m22 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m12 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m23 = 0.0;
+            }
+            if self
+                .flags
+                .contains(RigidBodyMassPropsFlags::ROTATION_LOCKED_Z)
+            {
+                self.effective_world_inv_inertia_sqrt.m33 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m13 = 0.0;
+                self.effective_world_inv_inertia_sqrt.m23 = 0.0;
+            }
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// The velocities of this rigid-body.
+pub struct RigidBodyVelocity {
+    /// The linear velocity of the rigid-body.
+    pub linvel: Vector<Real>,
+    /// The angular velocity of the rigid-body.
+    pub angvel: AngVector<Real>,
+}
+
+impl Default for RigidBodyVelocity {
+    fn default() -> Self {
+        Self::zero()
+    }
+}
+
+impl RigidBodyVelocity {
+    /// Velocities set to zero.
+    #[must_use]
+    pub fn zero() -> Self {
+        Self {
+            linvel: na::zero(),
+            angvel: na::zero(),
+        }
+    }
+
+    /// The approximate kinetic energy of this rigid-body.
+    ///
+    /// This approximation does not take the rigid-body's mass and angular inertia
+    /// into account.
+    #[must_use]
+    pub fn pseudo_kinetic_energy(&self) -> Real {
+        self.linvel.norm_squared() + self.angvel.gdot(self.angvel)
+    }
+
+    /// Returns the update velocities after applying the given damping.
+    #[must_use]
+    pub fn apply_damping(&self, dt: Real, damping: &RigidBodyDamping) -> Self {
+        RigidBodyVelocity {
+            linvel: self.linvel * (1.0 / (1.0 + dt * damping.linear_damping)),
+            angvel: self.angvel * (1.0 / (1.0 + dt * damping.angular_damping)),
+        }
+    }
+
+    /// The velocity of the given world-space point on this rigid-body.
+    #[must_use]
+    pub fn velocity_at_point(&self, point: &Point<Real>, world_com: &Point<Real>) -> Vector<Real> {
+        let dpt = point - world_com;
+        self.linvel + self.angvel.gcross(dpt)
+    }
+
+    /// Integrate the velocities in `self` to compute obtain new positions when moving from the given
+    /// inital position `init_pos`.
+    #[must_use]
+    pub fn integrate(
+        &self,
+        dt: Real,
+        init_pos: &Isometry<Real>,
+        local_com: &Point<Real>,
+    ) -> Isometry<Real> {
+        let com = init_pos * local_com;
+        let shift = Translation::from(com.coords);
+        let mut result =
+            shift * Isometry::new(self.linvel * dt, self.angvel * dt) * shift.inverse() * init_pos;
+        result.rotation.renormalize_fast();
+        result
+    }
+
+    /// Are these velocities exactly equal to zero?
+    #[must_use]
+    pub fn is_zero(&self) -> bool {
+        self.linvel.is_zero() && self.angvel.is_zero()
+    }
+
+    /// The kinetic energy of this rigid-body.
+    #[must_use]
+    pub fn kinetic_energy(&self, rb_mprops: &RigidBodyMassProps) -> Real {
+        let mut energy = (rb_mprops.mass() * self.linvel.norm_squared()) / 2.0;
+
+        #[cfg(feature = "dim2")]
+        if !rb_mprops.effective_world_inv_inertia_sqrt.is_zero() {
+            let inertia_sqrt = 1.0 / rb_mprops.effective_world_inv_inertia_sqrt;
+            energy += (inertia_sqrt * self.angvel).powi(2) / 2.0;
+        }
+
+        #[cfg(feature = "dim3")]
+        if !rb_mprops.effective_world_inv_inertia_sqrt.is_zero() {
+            let inertia_sqrt = rb_mprops
+                .effective_world_inv_inertia_sqrt
+                .inverse_unchecked();
+            energy += (inertia_sqrt * self.angvel).norm_squared() / 2.0;
+        }
+
+        energy
+    }
+
+    /// Applies an impulse at the center-of-mass of this rigid-body.
+    /// The impulse is applied right away, changing the linear velocity.
+    /// This does nothing on non-dynamic bodies.
+    pub fn apply_impulse(&mut self, rb_mprops: &RigidBodyMassProps, impulse: Vector<Real>) {
+        self.linvel += impulse * rb_mprops.effective_inv_mass;
+    }
+
+    /// Applies an angular impulse at the center-of-mass of this rigid-body.
+    /// The impulse is applied right away, changing the angular velocity.
+    /// This does nothing on non-dynamic bodies.
+    #[cfg(feature = "dim2")]
+    pub fn apply_torque_impulse(&mut self, rb_mprops: &RigidBodyMassProps, torque_impulse: Real) {
+        self.angvel += rb_mprops.effective_world_inv_inertia_sqrt
+            * (rb_mprops.effective_world_inv_inertia_sqrt * torque_impulse);
+    }
+
+    /// Applies an angular impulse at the center-of-mass of this rigid-body.
+    /// The impulse is applied right away, changing the angular velocity.
+    /// This does nothing on non-dynamic bodies.
+    #[cfg(feature = "dim3")]
+    pub fn apply_torque_impulse(
+        &mut self,
+        rb_mprops: &RigidBodyMassProps,
+        torque_impulse: Vector<Real>,
+    ) {
+        self.angvel += rb_mprops.effective_world_inv_inertia_sqrt
+            * (rb_mprops.effective_world_inv_inertia_sqrt * torque_impulse);
+    }
+
+    /// Applies an impulse at the given world-space point of this rigid-body.
+    /// The impulse is applied right away, changing the linear and/or angular velocities.
+    /// This does nothing on non-dynamic bodies.
+    pub fn apply_impulse_at_point(
+        &mut self,
+        rb_mprops: &RigidBodyMassProps,
+        impulse: Vector<Real>,
+        point: Point<Real>,
+    ) {
+        let torque_impulse = (point - rb_mprops.world_com).gcross(impulse);
+        self.apply_impulse(rb_mprops, impulse);
+        self.apply_torque_impulse(rb_mprops, torque_impulse);
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// Damping factors to progressively slow down a rigid-body.
+pub struct RigidBodyDamping {
+    /// Damping factor for gradually slowing down the translational motion of the rigid-body.
+    pub linear_damping: Real,
+    /// Damping factor for gradually slowing down the angular motion of the rigid-body.
+    pub angular_damping: Real,
+}
+
+impl Default for RigidBodyDamping {
+    fn default() -> Self {
+        Self {
+            linear_damping: 0.0,
+            angular_damping: 0.0,
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// The user-defined external forces applied to this rigid-body.
+pub struct RigidBodyForces {
+    /// Accumulation of external forces (only for dynamic bodies).
+    pub force: Vector<Real>,
+    /// Accumulation of external torques (only for dynamic bodies).
+    pub torque: AngVector<Real>,
+    /// Gravity is multiplied by this scaling factor before it's
+    /// applied to this rigid-body.
+    pub gravity_scale: Real,
+}
+
+impl Default for RigidBodyForces {
+    fn default() -> Self {
+        Self {
+            force: na::zero(),
+            torque: na::zero(),
+            gravity_scale: 1.0,
+        }
+    }
+}
+
+impl RigidBodyForces {
+    /// Integrate these forces to compute new velocities.
+    #[must_use]
+    pub fn integrate(
+        &self,
+        dt: Real,
+        init_vels: &RigidBodyVelocity,
+        mprops: &RigidBodyMassProps,
+    ) -> RigidBodyVelocity {
+        let linear_acc = self.force * mprops.effective_inv_mass;
+        let angular_acc = mprops.effective_world_inv_inertia_sqrt
+            * (mprops.effective_world_inv_inertia_sqrt * self.torque);
+
+        RigidBodyVelocity {
+            linvel: init_vels.linvel + linear_acc * dt,
+            angvel: init_vels.angvel + angular_acc * dt,
+        }
+    }
+
+    /// Adds to `self` the gravitational force that would result in a gravitational acceleration
+    /// equal to `gravity`.
+    pub fn add_gravity_acceleration(&mut self, gravity: &Vector<Real>, mass: Real) {
+        self.force += gravity * self.gravity_scale * mass;
+    }
+
+    /// Applies a force at the given world-space point of the rigid-body with the given mass properties.
+    pub fn apply_force_at_point(
+        &mut self,
+        rb_mprops: &RigidBodyMassProps,
+        force: Vector<Real>,
+        point: Point<Real>,
+    ) {
+        self.force += force;
+        self.torque += (point - rb_mprops.world_com).gcross(force);
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// Information used for Continuous-Collision-Detection.
+pub struct RigidBodyCcd {
+    /// The distance used by the CCD solver to decide if a movement would
+    /// result in a tunnelling problem.
+    pub ccd_thickness: Real,
+    /// The max distance between this rigid-body's center of mass and its
+    /// furthest collider point.
+    pub ccd_max_dist: Real,
+    /// Is CCD active for this rigid-body?
+    ///
+    /// If `self.ccd_enabled` is `true`, then this is automatically set to
+    /// `true` when the CCD solver detects that the rigid-body is moving fast
+    /// enough to potential cause a tunneling problem.
+    pub ccd_active: bool,
+    /// Is CCD enabled for this rigid-body?
+    pub ccd_enabled: bool,
+}
+
+impl Default for RigidBodyCcd {
+    fn default() -> Self {
+        Self {
+            ccd_thickness: 0.0,
+            ccd_max_dist: 0.0,
+            ccd_active: false,
+            ccd_enabled: false,
+        }
+    }
+}
+
+impl RigidBodyCcd {
+    /// The maximum velocity any point of any collider attached to this rigid-body
+    /// moving with the given velocity can have.
+    pub fn max_point_velocity(&self, vels: &RigidBodyVelocity) -> Real {
+        #[cfg(feature = "dim2")]
+        return vels.linvel.norm() + vels.angvel.abs() * self.ccd_max_dist;
+        #[cfg(feature = "dim3")]
+        return vels.linvel.norm() + vels.angvel.norm() * self.ccd_max_dist;
+    }
+
+    /// Is this rigid-body moving fast enough so that it may cause a tunneling problem?
+    pub fn is_moving_fast(
+        &self,
+        dt: Real,
+        vels: &RigidBodyVelocity,
+        forces: Option<&RigidBodyForces>,
+    ) -> bool {
+        // NOTE: for the threshold we don't use the exact CCD thickness. Theoretically, we
+        //       should use `self.rb_ccd.ccd_thickness - smallest_contact_dist` where `smallest_contact_dist`
+        //       is the deepest contact (the contact with the largest penetration depth, i.e., the
+        //       negative `dist` with the largest absolute value.
+        //       However, getting this penetration depth assumes querying the contact graph from
+        //       the narrow-phase, which can be pretty expensive. So we use the CCD thickness
+        //       divided by 10 right now. We will see in practice if this value is OK or if we
+        //       should use a smaller (to be less conservative) or larger divisor (to be more conservative).
+        let threshold = self.ccd_thickness / 10.0;
+
+        if let Some(forces) = forces {
+            let linear_part = (vels.linvel + forces.force * dt).norm();
+            #[cfg(feature = "dim2")]
+            let angular_part = (vels.angvel + forces.torque * dt).abs() * self.ccd_max_dist;
+            #[cfg(feature = "dim3")]
+            let angular_part = (vels.angvel + forces.torque * dt).norm() * self.ccd_max_dist;
+            let vel_with_forces = linear_part + angular_part;
+            vel_with_forces > threshold
+        } else {
+            self.max_point_velocity(vels) * dt > threshold
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// Internal identifiers used by the physics engine.
+pub struct RigidBodyIds {
+    pub(crate) joint_graph_index: RigidBodyGraphIndex,
+    pub(crate) active_island_id: usize,
+    pub(crate) active_set_id: usize,
+    pub(crate) active_set_offset: usize,
+    pub(crate) active_set_timestamp: u32,
+}
+
+impl Default for RigidBodyIds {
+    fn default() -> Self {
+        Self {
+            joint_graph_index: InteractionGraph::<(), ()>::invalid_graph_index(),
+            active_island_id: 0,
+            active_set_id: 0,
+            active_set_offset: 0,
+            active_set_timestamp: 0,
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug)]
+/// The set of colliders attached to this rigid-bodies.
+///
+/// This should not be modified manually unless you really know what
+/// you are doing (for example if you are trying to integrate Rapier
+/// to a game engine using its component-based interface).
+pub struct RigidBodyColliders(pub Vec<ColliderHandle>);
+
+impl Default for RigidBodyColliders {
+    fn default() -> Self {
+        Self(vec![])
+    }
+}
+
+impl RigidBodyColliders {
+    /// Detach a collider from this rigid-body.
+    pub fn detach_collider(
+        &mut self,
+        rb_changes: &mut RigidBodyChanges,
+        co_handle: ColliderHandle,
+    ) {
+        if let Some(i) = self.0.iter().position(|e| *e == co_handle) {
+            rb_changes.set(
+                RigidBodyChanges::MODIFIED | RigidBodyChanges::COLLIDERS,
+                true,
+            );
+            self.0.swap_remove(i);
+        }
+    }
+
+    /// Attach a collider to this rigid-body.
+    pub fn attach_collider(
+        &mut self,
+        rb_changes: &mut RigidBodyChanges,
+        rb_ccd: &mut RigidBodyCcd,
+        rb_mprops: &mut RigidBodyMassProps,
+        rb_pos: &RigidBodyPosition,
+        co_handle: ColliderHandle,
+        co_pos: &mut ColliderPosition,
+        co_parent: &ColliderParent,
+        co_shape: &ColliderShape,
+        co_mprops: &ColliderMassProperties,
+    ) {
+        rb_changes.set(
+            RigidBodyChanges::MODIFIED | RigidBodyChanges::COLLIDERS,
+            true,
+        );
+
+        co_pos.0 = rb_pos.position * co_parent.pos_wrt_parent;
+        rb_ccd.ccd_thickness = rb_ccd.ccd_thickness.min(co_shape.ccd_thickness());
+
+        let shape_bsphere = co_shape.compute_bounding_sphere(&co_parent.pos_wrt_parent);
+        rb_ccd.ccd_max_dist = rb_ccd
+            .ccd_max_dist
+            .max(shape_bsphere.center.coords.norm() + shape_bsphere.radius);
+
+        let mass_properties = co_mprops
+            .mass_properties(&**co_shape)
+            .transform_by(&co_parent.pos_wrt_parent);
+        self.0.push(co_handle);
+        rb_mprops.mass_properties += mass_properties;
+        rb_mprops.update_world_mass_properties(&rb_pos.position);
+    }
+
+    /// Update the positions of all the colliders attached to this rigid-body.
+    pub fn update_positions<Colliders>(
+        &self,
+        colliders: &mut Colliders,
+        modified_colliders: &mut Vec<ColliderHandle>,
+        parent_pos: &Isometry<Real>,
+    ) where
+        Colliders: ComponentSetMut<ColliderPosition>
+            + ComponentSetMut<ColliderChanges>
+            + ComponentSetOption<ColliderParent>,
+    {
+        for handle in &self.0 {
+            // NOTE: the ColliderParent component must exist if we enter this method.
+            let co_parent: &ColliderParent = colliders
+                .get(handle.0)
+                .expect("Could not find the ColliderParent component.");
+            let new_pos = parent_pos * co_parent.pos_wrt_parent;
+
+            // Set the modification flag so we can benefit from the modification-tracking
+            // when updating the narrow-phase/broad-phase afterwards.
+            colliders.map_mut_internal(handle.0, |co_changes: &mut ColliderChanges| {
+                if !co_changes.contains(ColliderChanges::MODIFIED) {
+                    modified_colliders.push(*handle);
+                }
+
+                *co_changes |= ColliderChanges::POSITION;
+            });
+            colliders.set_internal(handle.0, ColliderPosition(new_pos));
+        }
+    }
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Copy)]
+/// The dominance groups of a rigid-body.
+pub struct RigidBodyDominance(pub i8);
+
+impl Default for RigidBodyDominance {
+    fn default() -> Self {
+        RigidBodyDominance(0)
+    }
+}
+
+impl RigidBodyDominance {
+    /// The actually dominance group of this rigid-body, after taking into account its type.
+    pub fn effective_group(&self, status: &RigidBodyType) -> i16 {
+        if status.is_dynamic() {
+            self.0 as i16
+        } else {
+            i8::MAX as i16 + 1
+        }
+    }
+}
+
+/// The rb_activation status of a body.
+///
+/// This controls whether a body is sleeping or not.
+/// If the threshold is negative, the body never sleeps.
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+pub struct RigidBodyActivation {
+    /// The threshold pseudo-kinetic energy bellow which the body can fall asleep.
+    pub threshold: Real,
+    /// The current pseudo-kinetic energy of the body.
+    pub energy: Real,
+    /// Is this body already sleeping?
+    pub sleeping: bool,
+}
+
+impl Default for RigidBodyActivation {
+    fn default() -> Self {
+        Self::new_active()
+    }
+}
+
+impl RigidBodyActivation {
+    /// The default amount of energy bellow which a body can be put to sleep by nphysics.
+    pub fn default_threshold() -> Real {
+        0.01
+    }
+
+    /// Create a new rb_activation status initialised with the default rb_activation threshold and is active.
+    pub fn new_active() -> Self {
+        RigidBodyActivation {
+            threshold: Self::default_threshold(),
+            energy: Self::default_threshold() * 4.0,
+            sleeping: false,
+        }
+    }
+
+    /// Create a new rb_activation status initialised with the default rb_activation threshold and is inactive.
+    pub fn new_inactive() -> Self {
+        RigidBodyActivation {
+            threshold: Self::default_threshold(),
+            energy: 0.0,
+            sleeping: true,
+        }
+    }
+
+    /// Returns `true` if the body is not asleep.
+    #[inline]
+    pub fn is_active(&self) -> bool {
+        self.energy != 0.0
+    }
+
+    /// Wakes up this rigid-body.
+    #[inline]
+    pub fn wake_up(&mut self, strong: bool) {
+        self.sleeping = false;
+        if strong || self.energy == 0.0 {
+            self.energy = self.threshold.abs() * 2.0;
+        }
+    }
+
+    /// Put this rigid-body to sleep.
+    #[inline]
+    pub fn sleep(&mut self) {
+        self.energy = 0.0;
+        self.sleeping = true;
+    }
+}