Merge pull request #267 from dimforge/multibody

Implement multibody joints, and new velocity-based constraints solver

20 files changed, 2919 insertions, 902 deletions

diff --git a/src/dynamics/joint/ball_joint.rs b/src/dynamics/joint/ball_joint.rs
deleted file mode 100644
index 0b626c0..0000000
--- a/src/dynamics/joint/ball_joint.rs
+++ /dev/null
@@ -1,148 +0,0 @@
-use crate::dynamics::SpringModel;
-use crate::math::{Point, Real, Rotation, UnitVector, Vector};
-
-#[derive(Copy, Clone, PartialEq)]
-#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-/// A joint that removes all relative linear motion between a pair of points on two bodies.
-pub struct BallJoint {
-    /// Where the ball joint is attached on the first body, expressed in the first body local frame.
-    pub local_anchor1: Point<Real>,
-    /// Where the ball joint is attached on the second body, expressed in the second body local frame.
-    pub local_anchor2: Point<Real>,
-    /// The impulse applied by this joint on the first body.
-    ///
-    /// The impulse applied to the second body is given by `-impulse`.
-    pub impulse: Vector<Real>,
-
-    /// The target relative angular velocity the motor will attempt to reach.
-    #[cfg(feature = "dim2")]
-    pub motor_target_vel: Real,
-    /// The target relative angular velocity the motor will attempt to reach.
-    #[cfg(feature = "dim3")]
-    pub motor_target_vel: Vector<Real>,
-    /// The target angular position of this joint, expressed as an axis-angle.
-    pub motor_target_pos: Rotation<Real>,
-    /// The motor's stiffness.
-    /// See the documentation of `SpringModel` for more information on this parameter.
-    pub motor_stiffness: Real,
-    /// The motor's damping.
-    /// See the documentation of `SpringModel` for more information on this parameter.
-    pub motor_damping: Real,
-    /// The maximal impulse the motor is able to deliver.
-    pub motor_max_impulse: Real,
-    /// The angular impulse applied by the motor.
-    #[cfg(feature = "dim2")]
-    pub motor_impulse: Real,
-    /// The angular impulse applied by the motor.
-    #[cfg(feature = "dim3")]
-    pub motor_impulse: Vector<Real>,
-    /// The spring-like model used by the motor to reach the target velocity and .
-    pub motor_model: SpringModel,
-
-    /// Are the limits enabled for this joint?
-    pub limits_enabled: bool,
-    /// The axis of the limit cone for this joint, if the local-space of the first body.
-    pub limits_local_axis1: UnitVector<Real>,
-    /// The axis of the limit cone for this joint, if the local-space of the first body.
-    pub limits_local_axis2: UnitVector<Real>,
-    /// The maximum angle allowed between the two limit axes in world-space.
-    pub limits_angle: Real,
-    /// The impulse applied to enforce joint limits.
-    pub limits_impulse: Real,
-}
-
-impl BallJoint {
-    /// Creates a new Ball joint from two anchors given on the local spaces of the respective bodies.
-    pub fn new(local_anchor1: Point<Real>, local_anchor2: Point<Real>) -> Self {
-        Self::with_impulse(local_anchor1, local_anchor2, Vector::zeros())
-    }
-
-    pub(crate) fn with_impulse(
-        local_anchor1: Point<Real>,
-        local_anchor2: Point<Real>,
-        impulse: Vector<Real>,
-    ) -> Self {
-        Self {
-            local_anchor1,
-            local_anchor2,
-            impulse,
-            motor_target_vel: na::zero(),
-            motor_target_pos: Rotation::identity(),
-            motor_stiffness: 0.0,
-            motor_damping: 0.0,
-            motor_impulse: na::zero(),
-            motor_max_impulse: Real::MAX,
-            motor_model: SpringModel::default(),
-            limits_enabled: false,
-            limits_local_axis1: Vector::x_axis(),
-            limits_local_axis2: Vector::x_axis(),
-            limits_angle: Real::MAX,
-            limits_impulse: 0.0,
-        }
-    }
-
-    /// Can a SIMD constraint be used for resolving this joint?
-    pub fn supports_simd_constraints(&self) -> bool {
-        // SIMD ball constraints don't support motors and limits right now.
-        !self.limits_enabled
-            && (self.motor_max_impulse == 0.0
-                || (self.motor_stiffness == 0.0 && self.motor_damping == 0.0))
-    }
-
-    /// Set the spring-like model used by the motor to reach the desired target velocity and position.
-    pub fn configure_motor_model(&mut self, model: SpringModel) {
-        self.motor_model = model;
-    }
-
-    /// Sets the target velocity and velocity correction factor this motor.
-    #[cfg(feature = "dim2")]
-    pub fn configure_motor_velocity(&mut self, target_vel: Real, factor: Real) {
-        self.configure_motor(self.motor_target_pos, target_vel, 0.0, factor)
-    }
-
-    /// Sets the target velocity and velocity correction factor this motor.
-    #[cfg(feature = "dim3")]
-    pub fn configure_motor_velocity(&mut self, target_vel: Vector<Real>, factor: Real) {
-        self.configure_motor(self.motor_target_pos, target_vel, 0.0, factor)
-    }
-
-    /// Sets the target orientation this motor needs to reach.
-    pub fn configure_motor_position(
-        &mut self,
-        target_pos: Rotation<Real>,
-        stiffness: Real,
-        damping: Real,
-    ) {
-        self.configure_motor(target_pos, na::zero(), stiffness, damping)
-    }
-
-    /// Sets the target orientation this motor needs to reach.
-    #[cfg(feature = "dim2")]
-    pub fn configure_motor(
-        &mut self,
-        target_pos: Rotation<Real>,
-        target_vel: Real,
-        stiffness: Real,
-        damping: Real,
-    ) {
-        self.motor_target_vel = target_vel;
-        self.motor_target_pos = target_pos;
-        self.motor_stiffness = stiffness;
-        self.motor_damping = damping;
-    }
-
-    /// Configure both the target orientation and target velocity of the motor.
-    #[cfg(feature = "dim3")]
-    pub fn configure_motor(
-        &mut self,
-        target_pos: Rotation<Real>,
-        target_vel: Vector<Real>,
-        stiffness: Real,
-        damping: Real,
-    ) {
-        self.motor_target_vel = target_vel;
-        self.motor_target_pos = target_pos;
-        self.motor_stiffness = stiffness;
-        self.motor_damping = damping;
-    }
-}
diff --git a/src/dynamics/joint/fixed_joint.rs b/src/dynamics/joint/fixed_joint.rs
index 6424750..10c4d7e 100644
--- a/src/dynamics/joint/fixed_joint.rs
+++ b/src/dynamics/joint/fixed_joint.rs
@@ -1,38 +1,55 @@
-use crate::math::{Isometry, Real, SpacialVector};
+use crate::dynamics::{JointAxesMask, JointData};
+use crate::math::{Isometry, Point, Real};
 
-#[derive(Copy, Clone, PartialEq)]
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-/// A joint that prevents all relative movement between two bodies.
-///
-/// Given two frames of references, this joint aims to ensure these frame always coincide in world-space.
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub struct FixedJoint {
-    /// The frame of reference for the first body affected by this joint, expressed in the local frame
-    /// of the first body.
-    pub local_frame1: Isometry<Real>,
-    /// The frame of reference for the second body affected by this joint, expressed in the local frame
-    /// of the first body.
-    pub local_frame2: Isometry<Real>,
-    /// The impulse applied to the first body affected by this joint.
-    ///
-    /// The impulse applied to the second body affected by this joint is given by `-impulse`.
-    /// This combines both linear and angular impulses:
-    /// - In 2D, `impulse.xy()` gives the linear impulse, and `impulse.z` the angular impulse.
-    /// - In 3D, `impulse.xyz()` gives the linear impulse, and `(impulse[3], impulse[4], impulse[5])` the angular impulse.
-    pub impulse: SpacialVector<Real>,
+    data: JointData,
 }
 
 impl FixedJoint {
-    /// Creates a new fixed joint from the frames of reference of both bodies.
-    pub fn new(local_frame1: Isometry<Real>, local_frame2: Isometry<Real>) -> Self {
-        Self {
-            local_frame1,
-            local_frame2,
-            impulse: SpacialVector::zeros(),
-        }
+    pub fn new() -> Self {
+        #[cfg(feature = "dim2")]
+        let mask = JointAxesMask::X | JointAxesMask::Y | JointAxesMask::ANG_X;
+        #[cfg(feature = "dim3")]
+        let mask = JointAxesMask::X
+            | JointAxesMask::Y
+            | JointAxesMask::Z
+            | JointAxesMask::ANG_X
+            | JointAxesMask::ANG_Y
+            | JointAxesMask::ANG_Z;
+
+        let data = JointData::default().lock_axes(mask);
+        Self { data }
+    }
+
+    #[must_use]
+    pub fn local_frame1(mut self, local_frame: Isometry<Real>) -> Self {
+        self.data = self.data.local_frame1(local_frame);
+        self
+    }
+
+    #[must_use]
+    pub fn local_frame2(mut self, local_frame: Isometry<Real>) -> Self {
+        self.data = self.data.local_frame2(local_frame);
+        self
     }
 
-    /// Can a SIMD constraint be used for resolving this joint?
-    pub fn supports_simd_constraints(&self) -> bool {
-        true
+    #[must_use]
+    pub fn local_anchor1(mut self, anchor1: Point<Real>) -> Self {
+        self.data = self.data.local_anchor1(anchor1);
+        self
+    }
+
+    #[must_use]
+    pub fn local_anchor2(mut self, anchor2: Point<Real>) -> Self {
+        self.data = self.data.local_anchor2(anchor2);
+        self
+    }
+}
+
+impl Into<JointData> for FixedJoint {
+    fn into(self) -> JointData {
+        self.data
     }
 }
diff --git a/src/dynamics/joint/generic_joint.rs b/src/dynamics/joint/generic_joint.rs
deleted file mode 100644
index 78f1e84..0000000
--- a/src/dynamics/joint/generic_joint.rs
+++ /dev/null
@@ -1,144 +0,0 @@
-use crate::dynamics::{BallJoint, FixedJoint, PrismaticJoint, RevoluteJoint};
-use crate::math::{Isometry, Real, SpacialVector};
-use crate::na::{Rotation3, UnitQuaternion};
-
-#[derive(Copy, Clone, Debug, PartialEq)]
-#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-/// A joint that prevents all relative movement between two bodies.
-///
-/// Given two frames of references, this joint aims to ensure these frame always coincide in world-space.
-pub struct GenericJoint {
-    /// The frame of reference for the first body affected by this joint, expressed in the local frame
-    /// of the first body.
-    pub local_anchor1: Isometry<Real>,
-    /// The frame of reference for the second body affected by this joint, expressed in the local frame
-    /// of the first body.
-    pub local_anchor2: Isometry<Real>,
-    /// The impulse applied to the first body affected by this joint.
-    ///
-    /// The impulse applied to the second body affected by this joint is given by `-impulse`.
-    /// This combines both linear and angular impulses:
-    /// - In 2D, `impulse.xy()` gives the linear impulse, and `impulse.z` the angular impulse.
-    /// - In 3D, `impulse.xyz()` gives the linear impulse, and `(impulse[3], impulse[4], impulse[5])` the angular impulse.
-    pub impulse: SpacialVector<Real>,
-
-    pub min_position: SpacialVector<Real>,
-    pub max_position: SpacialVector<Real>,
-    pub min_velocity: SpacialVector<Real>,
-    pub max_velocity: SpacialVector<Real>,
-    /// The minimum negative impulse the joint can apply on each DoF. Must be <= 0.0
-    pub min_impulse: SpacialVector<Real>,
-    /// The maximum positive impulse the joint can apply on each DoF. Must be >= 0.0
-    pub max_impulse: SpacialVector<Real>,
-    /// The minimum negative position impulse the joint can apply on each DoF. Must be <= 0.0
-    pub min_pos_impulse: SpacialVector<Real>,
-    /// The maximum positive position impulse the joint can apply on each DoF. Must be >= 0.0
-    pub max_pos_impulse: SpacialVector<Real>,
-}
-
-impl GenericJoint {
-    /// Creates a new fixed joint from the frames of reference of both bodies.
-    pub fn new(local_anchor1: Isometry<Real>, local_anchor2: Isometry<Real>) -> Self {
-        Self {
-            local_anchor1,
-            local_anchor2,
-            impulse: SpacialVector::zeros(),
-            min_position: SpacialVector::zeros(),
-            max_position: SpacialVector::zeros(),
-            min_velocity: SpacialVector::zeros(),
-            max_velocity: SpacialVector::zeros(),
-            min_impulse: SpacialVector::repeat(-Real::MAX),
-            max_impulse: SpacialVector::repeat(Real::MAX),
-            min_pos_impulse: SpacialVector::repeat(-Real::MAX),
-            max_pos_impulse: SpacialVector::repeat(Real::MAX),
-        }
-    }
-
-    pub fn set_dof_vel(&mut self, dof: u8, target_vel: Real, max_force: Real) {
-        self.min_velocity[dof as usize] = target_vel;
-        self.max_velocity[dof as usize] = target_vel;
-        self.min_impulse[dof as usize] = -max_force;
-        self.max_impulse[dof as usize] = max_force;
-    }
-
-    pub fn free_dof(&mut self, dof: u8) {
-        self.min_position[dof as usize] = -Real::MAX;
-        self.max_position[dof as usize] = Real::MAX;
-        self.min_velocity[dof as usize] = -Real::MAX;
-        self.max_velocity[dof as usize] = Real::MAX;
-        self.min_impulse[dof as usize] = 0.0;
-        self.max_impulse[dof as usize] = 0.0;
-        self.min_pos_impulse[dof as usize] = 0.0;
-        self.max_pos_impulse[dof as usize] = 0.0;
-    }
-
-    pub fn set_dof_limits(&mut self, dof: u8, min: Real, max: Real) {
-        self.min_position[dof as usize] = min;
-        self.max_position[dof as usize] = max;
-    }
-}
-
-impl From<RevoluteJoint> for GenericJoint {
-    fn from(joint: RevoluteJoint) -> Self {
-        let basis1 = [*joint.local_axis1, joint.basis1[0], joint.basis1[1]];
-        let basis2 = [*joint.local_axis2, joint.basis2[0], joint.basis2[1]];
-        let quat1 = UnitQuaternion::from_basis_unchecked(&basis1);
-        let quat2 = UnitQuaternion::from_basis_unchecked(&basis2);
-        let local_anchor1 = Isometry::from_parts(joint.local_anchor1.coords.into(), quat1);
-        let local_anchor2 = Isometry::from_parts(joint.local_anchor2.coords.into(), quat2);
-
-        let mut result = Self::new(local_anchor1, local_anchor2);
-        result.free_dof(3);
-
-        if joint.motor_damping != 0.0 {
-            result.set_dof_vel(3, joint.motor_target_vel, joint.motor_max_impulse);
-        }
-
-        result.impulse[0] = joint.impulse[0];
-        result.impulse[1] = joint.impulse[1];
-        result.impulse[2] = joint.impulse[2];
-        result.impulse[3] = joint.motor_impulse;
-        result.impulse[4] = joint.impulse[3];
-        result.impulse[5] = joint.impulse[4];
-
-        result
-    }
-}
-
-impl From<BallJoint> for GenericJoint {
-    fn from(joint: BallJoint) -> Self {
-        let local_anchor1 = Isometry::new(joint.local_anchor1.coords, na::zero());
-        let local_anchor2 = Isometry::new(joint.local_anchor2.coords, na::zero());
-
-        let mut result = Self::new(local_anchor1, local_anchor2);
-        result.impulse[0] = joint.impulse[0];
-        result.impulse[1] = joint.impulse[1];
-        result.impulse[2] = joint.impulse[2];
-        result.free_dof(3);
-        result.free_dof(4);
-        result.free_dof(5);
-        result
-    }
-}
-
-impl From<PrismaticJoint> for GenericJoint {
-    fn from(joint: PrismaticJoint) -> Self {
-        let basis1 = [*joint.local_axis1, joint.basis1[0], joint.basis1[1]];
-        let basis2 = [*joint.local_axis2, joint.basis2[0], joint.basis2[1]];
-        let quat1 = UnitQuaternion::from_basis_unchecked(&basis1);
-        let quat2 = UnitQuaternion::from_basis_unchecked(&basis2);
-        let local_anchor1 = Isometry::from_parts(joint.local_anchor1.coords.into(), quat1);
-        let local_anchor2 = Isometry::from_parts(joint.local_anchor2.coords.into(), quat2);
-
-        let mut result = Self::new(local_anchor1, local_anchor2);
-        result.free_dof(0);
-        result.set_dof_limits(0, joint.limits[0], joint.limits[1]);
-        result
-    }
-}
-
-impl From<FixedJoint> for GenericJoint {
-    fn from(joint: FixedJoint) -> Self {
-        Self::new(joint.local_anchor1, joint.local_anchor2)
-    }
-}
diff --git a/src/dynamics/joint/impulse_joint/impulse_joint.rs b/src/dynamics/joint/impulse_joint/impulse_joint.rs
new file mode 100644
index 0000000..a12c533
--- /dev/null
+++ b/src/dynamics/joint/impulse_joint/impulse_joint.rs
@@ -0,0 +1,20 @@
+use crate::dynamics::{JointData, JointHandle, RigidBodyHandle};
+use crate::math::{Real, SpacialVector};
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, PartialEq)]
+/// A joint attached to two bodies.
+pub struct ImpulseJoint {
+    /// Handle to the first body attached to this joint.
+    pub body1: RigidBodyHandle,
+    /// Handle to the second body attached to this joint.
+    pub body2: RigidBodyHandle,
+
+    pub data: JointData,
+    pub impulses: SpacialVector<Real>,
+
+    // A joint needs to know its handle to simplify its removal.
+    pub(crate) handle: JointHandle,
+    #[cfg(feature = "parallel")]
+    pub(crate) constraint_index: usize,
+}
diff --git a/src/dynamics/joint/joint_set.rs b/src/dynamics/joint/impulse_joint/impulse_joint_set.rs
index aba2aa8..183b668 100644
--- a/src/dynamics/joint/joint_set.rs
+++ b/src/dynamics/joint/impulse_joint/impulse_joint_set.rs
@@ -1,10 +1,10 @@
-use super::Joint;
+use super::ImpulseJoint;
 use crate::geometry::{InteractionGraph, RigidBodyGraphIndex, TemporaryInteractionIndex};
 
 use crate::data::arena::Arena;
 use crate::data::{BundleSet, Coarena, ComponentSet, ComponentSetMut};
 use crate::dynamics::{IslandManager, RigidBodyActivation, RigidBodyIds, RigidBodyType};
-use crate::dynamics::{JointParams, RigidBodyHandle};
+use crate::dynamics::{JointData, RigidBodyHandle};
 
 /// The unique identifier of a joint added to the joint set.
 /// The unique identifier of a collider added to a collider set.
@@ -34,19 +34,19 @@ impl JointHandle {
 }
 
 pub(crate) type JointIndex = usize;
-pub(crate) type JointGraphEdge = crate::data::graph::Edge<Joint>;
+pub(crate) type JointGraphEdge = crate::data::graph::Edge<ImpulseJoint>;
 
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
 #[derive(Clone, Default)]
-/// A set of joints that can be handled by a physics `World`.
-pub struct JointSet {
+/// A set of impulse_joints that can be handled by a physics `World`.
+pub struct ImpulseJointSet {
     rb_graph_ids: Coarena<RigidBodyGraphIndex>,
     joint_ids: Arena<TemporaryInteractionIndex>, // Map joint handles to edge ids on the graph.
-    joint_graph: InteractionGraph<RigidBodyHandle, Joint>,
+    joint_graph: InteractionGraph<RigidBodyHandle, ImpulseJoint>,
 }
 
-impl JointSet {
-    /// Creates a new empty set of joints.
+impl ImpulseJointSet {
+    /// Creates a new empty set of impulse_joints.
     pub fn new() -> Self {
         Self {
             rb_graph_ids: Coarena::new(),
@@ -55,26 +55,26 @@ impl JointSet {
         }
     }
 
-    /// The number of joints on this set.
+    /// The number of impulse_joints on this set.
     pub fn len(&self) -> usize {
         self.joint_graph.graph.edges.len()
     }
 
-    /// `true` if there are no joints in this set.
+    /// `true` if there are no impulse_joints in this set.
     pub fn is_empty(&self) -> bool {
         self.joint_graph.graph.edges.is_empty()
     }
 
-    /// Retrieve the joint graph where edges are joints and nodes are rigid body handles.
-    pub fn joint_graph(&self) -> &InteractionGraph<RigidBodyHandle, Joint> {
+    /// Retrieve the joint graph where edges are impulse_joints and nodes are rigid body handles.
+    pub fn joint_graph(&self) -> &InteractionGraph<RigidBodyHandle, ImpulseJoint> {
         &self.joint_graph
     }
 
-    /// Iterates through all the joitns attached to the given rigid-body.
+    /// Iterates through all the impulse_joints attached to the given rigid-body.
     pub fn joints_with<'a>(
         &'a self,
         body: RigidBodyHandle,
-    ) -> impl Iterator<Item = (RigidBodyHandle, RigidBodyHandle, &'a Joint)> {
+    ) -> impl Iterator<Item = (RigidBodyHandle, RigidBodyHandle, &'a ImpulseJoint)> {
         self.rb_graph_ids
             .get(body.0)
             .into_iter()
@@ -87,13 +87,13 @@ impl JointSet {
     }
 
     /// Gets the joint with the given handle.
-    pub fn get(&self, handle: JointHandle) -> Option<&Joint> {
+    pub fn get(&self, handle: JointHandle) -> Option<&ImpulseJoint> {
         let id = self.joint_ids.get(handle.0)?;
         self.joint_graph.graph.edge_weight(*id)
     }
 
     /// Gets a mutable reference to the joint with the given handle.
-    pub fn get_mut(&mut self, handle: JointHandle) -> Option<&mut Joint> {
+    pub fn get_mut(&mut self, handle: JointHandle) -> Option<&mut ImpulseJoint> {
         let id = self.joint_ids.get(handle.0)?;
         self.joint_graph.graph.edge_weight_mut(*id)
     }
@@ -107,7 +107,7 @@ impl JointSet {
     ///
     /// Using this is discouraged in favor of `self.get(handle)` which does not
     /// suffer form the ABA problem.
-    pub fn get_unknown_gen(&self, i: u32) -> Option<(&Joint, JointHandle)> {
+    pub fn get_unknown_gen(&self, i: u32) -> Option<(&ImpulseJoint, JointHandle)> {
         let (id, handle) = self.joint_ids.get_unknown_gen(i)?;
         Some((
             self.joint_graph.graph.edge_weight(*id)?,
@@ -124,7 +124,7 @@ impl JointSet {
     ///
     /// Using this is discouraged in favor of `self.get_mut(handle)` which does not
     /// suffer form the ABA problem.
-    pub fn get_unknown_gen_mut(&mut self, i: u32) -> Option<(&mut Joint, JointHandle)> {
+    pub fn get_unknown_gen_mut(&mut self, i: u32) -> Option<(&mut ImpulseJoint, JointHandle)> {
         let (id, handle) = self.joint_ids.get_unknown_gen(i)?;
         Some((
             self.joint_graph.graph.edge_weight_mut(*id)?,
@@ -133,7 +133,7 @@ impl JointSet {
     }
 
     /// Iterates through all the joint on this set.
-    pub fn iter(&self) -> impl Iterator<Item = (JointHandle, &Joint)> {
+    pub fn iter(&self) -> impl Iterator<Item = (JointHandle, &ImpulseJoint)> {
         self.joint_graph
             .graph
             .edges
@@ -142,7 +142,7 @@ impl JointSet {
     }
 
     /// Iterates mutably through all the joint on this set.
-    pub fn iter_mut(&mut self) -> impl Iterator<Item = (JointHandle, &mut Joint)> {
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (JointHandle, &mut ImpulseJoint)> {
         self.joint_graph
             .graph
             .edges
@@ -150,8 +150,8 @@ impl JointSet {
             .map(|e| (e.weight.handle, &mut e.weight))
     }
 
-    // /// The set of joints as an array.
-    // pub(crate) fn joints(&self) -> &[JointGraphEdge] {
+    // /// The set of impulse_joints as an array.
+    // pub(crate) fn impulse_joints(&self) -> &[JointGraphEdge] {
     //     // self.joint_graph
     //     //     .graph
     //     //     .edges
@@ -170,25 +170,22 @@ impl JointSet {
     }
 
     /// Inserts a new joint into this set and retrieve its handle.
-    pub fn insert<J>(
+    pub fn insert(
         &mut self,
         body1: RigidBodyHandle,
         body2: RigidBodyHandle,
-        joint_params: J,
-    ) -> JointHandle
-    where
-        J: Into<JointParams>,
-    {
+        data: impl Into<JointData>,
+    ) -> JointHandle {
+        let data = data.into();
         let handle = self.joint_ids.insert(0.into());
-        let joint = Joint {
+        let joint = ImpulseJoint {
             body1,
             body2,
+            data,
+            impulses: na::zero(),
             handle: JointHandle(handle),
             #[cfg(feature = "parallel")]
             constraint_index: 0,
-            #[cfg(feature = "parallel")]
-            position_constraint_index: 0,
-            params: joint_params.into(),
         };
 
         let default_id = InteractionGraph::<(), ()>::invalid_graph_index();
@@ -201,12 +198,12 @@ impl JointSet {
 
         // NOTE: the body won't have a graph index if it does not
         // have any joint attached.
-        if !InteractionGraph::<RigidBodyHandle, Joint>::is_graph_index_valid(graph_index1) {
+        if !InteractionGraph::<RigidBodyHandle, ImpulseJoint>::is_graph_index_valid(graph_index1) {
             graph_index1 = self.joint_graph.graph.add_node(joint.body1);
             self.rb_graph_ids.insert(joint.body1.0, graph_index1);
         }
 
-        if !InteractionGraph::<RigidBodyHandle, Joint>::is_graph_index_valid(graph_index2) {
+        if !InteractionGraph::<RigidBodyHandle, ImpulseJoint>::is_graph_index_valid(graph_index2) {
             graph_index2 = self.joint_graph.graph.add_node(joint.body2);
             self.rb_graph_ids.insert(joint.body2.0, graph_index2);
         }
@@ -215,7 +212,7 @@ impl JointSet {
         JointHandle(handle)
     }
 
-    /// Retrieve all the joints happening between two active bodies.
+    /// Retrieve all the impulse_joints happening between two active bodies.
     // NOTE: this is very similar to the code from NarrowPhase::select_active_interactions.
     pub(crate) fn select_active_interactions<Bodies>(
         &self,
@@ -271,7 +268,7 @@ impl JointSet {
         islands: &mut IslandManager,
         bodies: &mut Bodies,
         wake_up: bool,
-    ) -> Option<Joint>
+    ) -> Option<ImpulseJoint>
     where
         Bodies: ComponentSetMut<RigidBodyActivation>
             + ComponentSet<RigidBodyType>
@@ -299,11 +296,11 @@ impl JointSet {
         removed_joint
     }
 
-    /// Deletes all the joints attached to the given rigid-body.
+    /// Deletes all the impulse_joints attached to the given rigid-body.
     ///
     /// The provided rigid-body handle is not required to identify a rigid-body that
     /// is still contained by the `bodies` component set.
-    /// Returns the (now invalid) handles of the removed joints.
+    /// Returns the (now invalid) handles of the removed impulse_joints.
     pub fn remove_joints_attached_to_rigid_body<Bodies>(
         &mut self,
         handle: RigidBodyHandle,
diff --git a/src/dynamics/joint/impulse_joint/mod.rs b/src/dynamics/joint/impulse_joint/mod.rs
new file mode 100644
index 0000000..2afe078
--- /dev/null
+++ b/src/dynamics/joint/impulse_joint/mod.rs
@@ -0,0 +1,6 @@
+pub use self::impulse_joint::ImpulseJoint;
+pub use self::impulse_joint_set::{ImpulseJointSet, JointHandle};
+pub(crate) use self::impulse_joint_set::{JointGraphEdge, JointIndex};
+
+mod impulse_joint;
+mod impulse_joint_set;
diff --git a/src/dynamics/joint/joint.rs b/src/dynamics/joint/joint.rs
deleted file mode 100644
index 0c2c864..0000000
--- a/src/dynamics/joint/joint.rs
+++ /dev/null
@@ -1,143 +0,0 @@
-#[cfg(feature = "dim3")]
-use crate::dynamics::RevoluteJoint;
-use crate::dynamics::{BallJoint, FixedJoint, JointHandle, PrismaticJoint, RigidBodyHandle};
-
-#[derive(Copy, Clone, PartialEq)]
-#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-/// An enum grouping all possible types of joints.
-pub enum JointParams {
-    /// A Ball joint that removes all relative linear degrees of freedom between the affected bodies.
-    BallJoint(BallJoint),
-    /// A fixed joint that removes all relative degrees of freedom between the affected bodies.
-    FixedJoint(FixedJoint),
-    /// A prismatic joint that removes all degrees of degrees of freedom between the affected
-    /// bodies except for the translation along one axis.
-    PrismaticJoint(PrismaticJoint),
-    #[cfg(feature = "dim3")]
-    /// A revolute joint that removes all degrees of degrees of freedom between the affected
-    /// bodies except for the translation along one axis.
-    RevoluteJoint(RevoluteJoint),
-    // GenericJoint(GenericJoint),
-}
-
-impl JointParams {
-    /// An integer identifier for each type of joint.
-    pub fn type_id(&self) -> usize {
-        match self {
-            JointParams::BallJoint(_) => 0,
-            JointParams::FixedJoint(_) => 1,
-            JointParams::PrismaticJoint(_) => 2,
-            // JointParams::GenericJoint(_) => 3,
-            #[cfg(feature = "dim3")]
-            JointParams::RevoluteJoint(_) => 4,
-        }
-    }
-
-    /// Gets a reference to the underlying ball joint, if `self` is one.
-    pub fn as_ball_joint(&self) -> Option<&BallJoint> {
-        if let JointParams::BallJoint(j) = self {
-            Some(j)
-        } else {
-            None
-        }
-    }
-
-    /// Gets a reference to the underlying fixed joint, if `self` is one.
-    pub fn as_fixed_joint(&self) -> Option<&FixedJoint> {
-        if let JointParams::FixedJoint(j) = self {
-            Some(j)
-        } else {
-            None
-        }
-    }
-
-    // /// Gets a reference to the underlying generic joint, if `self` is one.
-    // pub fn as_generic_joint(&self) -> Option<&GenericJoint> {
-    //     if let JointParams::GenericJoint(j) = self {
-    //         Some(j)
-    //     } else {
-    //         None
-    //     }
-    // }
-
-    /// Gets a reference to the underlying prismatic joint, if `self` is one.
-    pub fn as_prismatic_joint(&self) -> Option<&PrismaticJoint> {
-        if let JointParams::PrismaticJoint(j) = self {
-            Some(j)
-        } else {
-            None
-        }
-    }
-
-    /// Gets a reference to the underlying revolute joint, if `self` is one.
-    #[cfg(feature = "dim3")]
-    pub fn as_revolute_joint(&self) -> Option<&RevoluteJoint> {
-        if let JointParams::RevoluteJoint(j) = self {
-            Some(j)
-        } else {
-            None
-        }
-    }
-}
-
-impl From<BallJoint> for JointParams {
-    fn from(j: BallJoint) -> Self {
-        JointParams::BallJoint(j)
-    }
-}
-
-impl From<FixedJoint> for JointParams {
-    fn from(j: FixedJoint) -> Self {
-        JointParams::FixedJoint(j)
-    }
-}
-
-// impl From<GenericJoint> for JointParams {
-//     fn from(j: GenericJoint) -> Self {
-//         JointParams::GenericJoint(j)
-//     }
-// }
-
-#[cfg(feature = "dim3")]
-impl From<RevoluteJoint> for JointParams {
-    fn from(j: RevoluteJoint) -> Self {
-        JointParams::RevoluteJoint(j)
-    }
-}
-
-impl From<PrismaticJoint> for JointParams {
-    fn from(j: PrismaticJoint) -> Self {
-        JointParams::PrismaticJoint(j)
-    }
-}
-
-#[cfg_attr(featu