Merge pull request #28 from dimforge/raycast

Add the QueryPipeline for ray-casting and other geometrical queries in the future

37 files changed, 1768 insertions, 694 deletions

diff --git a/.github/workflows/rapier-ci-bench.yml b/.github/workflows/rapier-ci-bench.yml
index 89ed247..9cce1b2 100644
--- a/.github/workflows/rapier-ci-bench.yml
+++ b/.github/workflows/rapier-ci-bench.yml
@@ -9,20 +9,23 @@ on:
 
 jobs:
   send-bench-message:
+    env:
+      BENCHBOT_AMQP_USER: ${{ secrets.BENCHBOT_AMQP_USER }}
+      BENCHBOT_AMQP_PASS: ${{ secrets.BENCHBOT_AMQP_PASS }}
+      BENCHBOT_AMQP_VHOST: ${{ secrets.BENCHBOT_AMQP_VHOST }}
+      BENCHBOT_AMQP_HOST: ${{ secrets.BENCHBOT_AMQP_HOST }}
+      BENCHBOT_TARGET_REPO: ${{ github.repository }}
+      BENCHBOT_TARGET_COMMIT: ${{ github.event.pull_request.head.sha }}
+      BENCHBOT_SHA: ${{ github.sha }}
+      BENCHBOT_HEAD_REF: ${{github.head_ref}}
     runs-on: ubuntu-latest
     steps:
-      - name: Get the latest commit on PR
-        id: get-latest-commit
-        uses: ActionsRML/get-PR-latest-commit@v1
+      - name: Find commit SHA
+        if: github.ref == 'refs/heads/master'
+        run: |
+          echo "::set-env name=BENCHBOT_TARGET_COMMIT::$BENCHBOT_SHA"
       - name: Send 3D bench message
         shell: bash
-        env:
-          BENCHBOT_AMQP_USER: ${{ secrets.BENCHBOT_AMQP_USER }}
-          BENCHBOT_AMQP_PASS: ${{ secrets.BENCHBOT_AMQP_PASS }}
-          BENCHBOT_AMQP_VHOST: ${{ secrets.BENCHBOT_AMQP_VHOST }}
-          BENCHBOT_AMQP_HOST: ${{ secrets.BENCHBOT_AMQP_HOST }}
-          BENCHBOT_TARGET_REPO: ${{ github.repository }}
-          BENCHBOT_TARGET_COMMIT: ${{ steps.get-latest-commit.outputs.latest_commit_sha }}
         run: curl -u $BENCHBOT_AMQP_USER:$BENCHBOT_AMQP_PASS
              -i -H "content-type:application/json" -X POST
              https://$BENCHBOT_AMQP_HOST/api/exchanges/$BENCHBOT_AMQP_VHOST//publish
diff --git a/CHANGELOG b/CHANGELOG
index 9e4731e..70b20e5 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,10 +1,15 @@
 ## v0.2.0 - WIP
+The most significant change on this version is the addition of the `QueryPipeline` responsible for performing
+scene-wide queries. So far only ray-casting has been implemented.
 
-- Add `PhysicsPipeline::remove_collider(...)` to remove a collider from the `ColliderSet`.
+- Add `ColliderSet::remove(...)` to remove a collider from the `ColliderSet`.
+- Replace `PhysicsPipeline::remove_rigid_body` by `RigidBodySet::remove`.
+- The `JointSet.iter()` now returns an iterator yielding `(JointHandle, &Joint)` instead of just `&Joint`.
 - Add `ColliderDesc::translation(...)` to set the translation of a collider relative to the rigid-body it is attached to.
 - Add `ColliderDesc::rotation(...)` to set the rotation of a collider relative to the rigid-body it is attached to.
 - Add `ColliderDesc::position(...)` to set the position of a collider relative to the rigid-body it is attached to.
 - Add `Collider::position_wrt_parent()` to get the position of a collider relative to the rigid-body it is attached to.
+- Modify `RigidBody::set_position(...)` so it also resets the next kinematic position to the same value.
 - Deprecate `Collider::delta()` in favor of the new `Collider::position_wrt_parent()`.
 - Fix multiple issues occurring when having colliders resulting in a non-zero center-of-mass.
 - Fix a crash happening when removing a rigid-body with a collider, stepping the simulation, adding another rigid-body
diff --git a/Cargo.toml b/Cargo.toml
index b4ce57e..944fa40 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,7 @@ members = [ "build/rapier2d", "build/rapier_testbed2d", "examples2d", "benchmark
 
 [patch.crates-io]
 #wrapped2d = { git = "https://github.com/Bastacyclop/rust_box2d.git" }
+#simba = { path = "../simba" }
 
 [profile.release]
 #debug = true
diff --git a/build/rapier2d/Cargo.toml b/build/rapier2d/Cargo.toml
index ec3a026..890dfe2 100644
--- a/build/rapier2d/Cargo.toml
+++ b/build/rapier2d/Cargo.toml
@@ -37,7 +37,7 @@ instant = { version = "0.1", features = [ "now" ]}
 num-traits = "0.2"
 nalgebra = "0.22"
 ncollide2d = "0.24"
-simba = "0.2"
+simba = "^0.2.1"
 approx = "0.3"
 rayon = { version = "1", optional = true }
 crossbeam = "0.7"
diff --git a/build/rapier3d/Cargo.toml b/build/rapier3d/Cargo.toml
index dcf5aca..298d655 100644
--- a/build/rapier3d/Cargo.toml
+++ b/build/rapier3d/Cargo.toml
@@ -37,7 +37,7 @@ instant = { version = "0.1", features = [ "now" ]}
 num-traits = "0.2"
 nalgebra = "0.22"
 ncollide3d = "0.24"
-simba = "0.2"
+simba = "^0.2.1"
 approx = "0.3"
 rayon = { version = "1", optional = true }
 crossbeam = "0.7"
diff --git a/examples2d/add_remove2.rs b/examples2d/add_remove2.rs
index 3a32a95..67075fe 100644
--- a/examples2d/add_remove2.rs
+++ b/examples2d/add_remove2.rs
@@ -28,14 +28,9 @@ pub fn init_world(testbed: &mut Testbed) {
             .map(|e| e.0)
             .collect();
         for handle in to_remove {
-            physics.pipeline.remove_rigid_body(
-                handle,
-                &mut physics.broad_phase,
-                &mut physics.narrow_phase,
-                &mut physics.bodies,
-                &mut physics.colliders,
-                &mut physics.joints,
-            );
+            physics
+                .bodies
+                .remove(handle, &mut physics.colliders, &mut physics.joints);
             graphics.remove_body_nodes(window, handle);
         }
     });
diff --git a/examples3d/add_remove3.rs b/examples3d/add_remove3.rs
index 17aad44..6b58adf 100644
--- a/examples3d/add_remove3.rs
+++ b/examples3d/add_remove3.rs
@@ -28,14 +28,9 @@ pub fn init_world(testbed: &mut Testbed) {
             .map(|e| e.0)
             .collect();
         for handle in to_remove {
-            physics.pipeline.remove_rigid_body(
-                handle,
-                &mut physics.broad_phase,
-                &mut physics.narrow_phase,
-                &mut physics.bodies,
-                &mut physics.colliders,
-                &mut physics.joints,
-            );
+            physics
+                .bodies
+                .remove(handle, &mut physics.colliders, &mut physics.joints);
             graphics.remove_body_nodes(window, handle);
         }
     });
diff --git a/examples3d/platform3.rs b/examples3d/platform3.rs
index 3836baf..6c3483e 100644
--- a/examples3d/platform3.rs
+++ b/examples3d/platform3.rs
@@ -64,22 +64,29 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Setup a callback to control the platform.
      */
+    let mut count = 0;
     testbed.add_callback(move |_, physics, _, _, time| {
-        let mut platform = physics.bodies.get_mut(platform_handle).unwrap();
-        let mut next_pos = platform.position;
+        count += 1;
+        if count % 100 > 50 {
+            return;
+        }
 
-        let dt = 0.016;
-        next_pos.translation.vector.y += (time * 5.0).sin() * dt;
-        next_pos.translation.vector.z += time.sin() * 5.0 * dt;
+        if let Some(mut platform) = physics.bodies.get_mut(platform_handle) {
+            let mut next_pos = platform.position;
 
-        if next_pos.translation.vector.z >= rad * 10.0 {
-            next_pos.translation.vector.z -= dt;
-        }
-        if next_pos.translation.vector.z <= -rad * 10.0 {
-            next_pos.translation.vector.z += dt;
-        }
+            let dt = 0.016;
+            next_pos.translation.vector.y += (time * 5.0).sin() * dt;
+            next_pos.translation.vector.z += time.sin() * 5.0 * dt;
 
-        platform.set_next_kinematic_position(next_pos);
+            if next_pos.translation.vector.z >= rad * 10.0 {
+                next_pos.translation.vector.z -= dt;
+            }
+            if next_pos.translation.vector.z <= -rad * 10.0 {
+                next_pos.translation.vector.z += dt;
+            }
+
+            platform.set_next_kinematic_position(next_pos);
+        }
     });
 
     /*
diff --git a/src/data/mod.rs b/src/data/mod.rs
index 7c00442..5d3efa6 100644
--- a/src/data/mod.rs
+++ b/src/data/mod.rs
@@ -2,3 +2,4 @@
 
 pub mod arena;
 pub(crate) mod graph;
+pub mod pubsub;
diff --git a/src/data/pubsub.rs b/src/data/pubsub.rs
new file mode 100644
index 0000000..b2c9e27
--- /dev/null
+++ b/src/data/pubsub.rs
@@ -0,0 +1,175 @@
+//! Publish-subscribe mechanism for internal events.
+
+use std::collections::VecDeque;
+use std::marker::PhantomData;
+
+/// A permanent subscription to a pub-sub queue.
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+pub struct Subscription<T> {
+    // Position on the cursor array.
+    id: u32,
+    _phantom: PhantomData<T>,
+}
+
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+struct PubSubCursor {
+    // Position on the offset array.
+    id: u32,
+    // Index of the next message to read.
+    // NOTE: Having this here is not actually necessary because
+    // this value is supposed to be equal to `offsets[self.id]`.
+    // However, we keep it because it lets us avoid one lookup
+    // on the `offsets` array inside of message-polling loops
+    // based on `read_ith`.
+    next: u32,
+}
+
+impl PubSubCursor {
+    fn id(&self, num_deleted: u32) -> usize {
+        (self.id - num_deleted) as usize
+    }
+
+    fn next(&self, num_deleted: u32) -> usize {
+        (self.next - num_deleted) as usize
+    }
+}
+
+/// A pub-sub queue.
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+pub struct PubSub<T> {
+    deleted_messages: u32,
+    deleted_offsets: u32,
+    messages: VecDeque<T>,
+    offsets: VecDeque<u32>,
+    cursors: Vec<PubSubCursor>,
+}
+
+impl<T> PubSub<T> {
+    /// Create a new empty pub-sub queue.
+    pub fn new() -> Self {
+        Self {
+            deleted_offsets: 0,
+            deleted_messages: 0,
+            messages: VecDeque::new(),
+            offsets: VecDeque::new(),
+            cursors: Vec::new(),
+        }
+    }
+
+    fn reset_shifts(&mut self) {
+        for offset in &mut self.offsets {
+            *offset -= self.deleted_messages;
+        }
+
+        for cursor in &mut self.cursors {
+            cursor.id -= self.deleted_offsets;
+            cursor.next -= self.deleted_messages;
+        }
+
+        self.deleted_offsets = 0;
+        self.deleted_messages = 0;
+    }
+
+    /// Publish a new message.
+    pub fn publish(&mut self, message: T) {
+        if self.offsets.is_empty() {
+            // No subscribers, drop the message.
+            return;
+        }
+
+        self.messages.push_back(message);
+    }
+
+    /// Subscribe to the queue.
+    ///
+    /// A subscription cannot be cancelled.
+    #[must_use]
+    pub fn subscribe(&mut self) -> Subscription<T> {
+        let cursor = PubSubCursor {
+            next: self.messages.len() as u32 + self.deleted_messages,
+            id: self.offsets.len() as u32 + self.deleted_offsets,
+        };
+
+        let subscription = Subscription {
+            id: self.cursors.len() as u32,
+            _phantom: PhantomData,
+        };
+
+        self.offsets.push_back(cursor.next);
+        self.cursors.push(cursor);
+        subscription
+    }
+
+    /// Read the i-th message not yet read by the given subsciber.
+    pub fn read_ith(&self, sub: &Subscription<T>, i: usize) -> Option<&T> {
+        let cursor = &self.cursors[sub.id as usize];
+        self.messages
+            .get(cursor.next(self.deleted_messages) as usize + i)
+    }
+
+    /// Get the messages not yet read by the given subscriber.
+    pub fn read(&self, sub: &Subscription<T>) -> impl Iterator<Item = &T> {
+        let cursor = &self.cursors[sub.id as usize];
+        let next = cursor.next(self.deleted_messages);
+
+        // TODO: use self.queue.range(next..) once it is stabilised.
+        MessageRange {
+            queue: &self.messages,
+            next,
+        }
+    }
+
+    /// Makes the given subscribe acknowledge all the messages in the queue.
+    ///
+    /// A subscriber cannot read acknowledged messages any more.
+    pub fn ack(&mut self, sub: &Subscription<T>) {
+        // Update the cursor.
+        let cursor = &mut self.cursors[sub.id as usize];
+
+        self.offsets[cursor.id(self.deleted_offsets)] = u32::MAX;
+        cursor.id = self.offsets.len() as u32 + self.deleted_offsets;
+
+        cursor.next = self.messages.len() as u32 + self.deleted_messages;
+        self.offsets.push_back(cursor.next);
+
+        // Now clear the messages we don't need to
+        // maintain in memory anymore.
+        while self.offsets.front() == Some(&u32::MAX) {
+            self.offsets.pop_front();
+            self.deleted_offsets += 1;
+        }
+
+        // There must be at least one offset otherwise
+        // that would mean we have no subscribers.
+        let next = self.offsets.front().unwrap();
+        let num_to_delete = *next - self.deleted_messages;
+
+        for _ in 0..num_to_delete {
+            self.messages.pop_front();
+        }
+
+        self.deleted_messages += num_to_delete;
+
+        if self.deleted_messages > u32::MAX / 2 || self.deleted_offsets > u32::MAX / 2 {
+            // Don't let the deleted_* shifts grow indefinitely otherwise
+            // they will end up overflowing, breaking everything.
+            self.reset_shifts();
+        }
+    }
+}
+
+struct MessageRange<'a, T> {
+    queue: &'a VecDeque<T>,
+    next: usize,
+}
+
+impl<'a, T> Iterator for MessageRange<'a, T> {
+    type Item = &'a T;
+
+    #[inline(always)]
+    fn next(&mut self) -> Option<&'a T> {
+        let result = self.queue.get(self.next);
+        self.next += 1;
+        result
+    }
+}
diff --git a/src/dynamics/integration_parameters.rs b/src/dynamics/integration_parameters.rs
index faf22e1..b31c3f6 100644
--- a/src/dynamics/integration_parameters.rs
+++ b/src/dynamics/integration_parameters.rs
@@ -2,7 +2,7 @@
 #[derive(Clone)]
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
 pub struct IntegrationParameters {
-    /// The timestep (default: `1.0 / 60.0`)
+    /// The timestep length (default: `1.0 / 60.0`)
     dt: f32,
     /// The inverse of `dt`.
     inv_dt: f32,
diff --git a/src/dynamics/joint/joint_set.rs b/src/dynamics/joint/joint_set.rs
index 51d7432..2b1895f 100644
--- a/src/dynamics/joint/joint_set.rs
+++ b/src/dynamics/joint/joint_set.rs
@@ -66,17 +66,21 @@ impl JointSet {
     }
 
     /// Iterates through all the joint on this set.
-    pub fn iter(&self) -> impl Iterator<Item = &Joint> {
-        self.joint_graph.graph.edges.iter().map(|e| &e.weight)
+    pub fn iter(&self) -> impl Iterator<Item = (JointHandle, &Joint)> {
+        self.joint_graph
+            .graph
+            .edges
+            .iter()
+            .map(|e| (e.weight.handle, &e.weight))
     }
 
     /// Iterates mutably through all the joint on this set.
-    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut Joint> {
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (JointHandle, &mut Joint)> {
         self.joint_graph
             .graph
             .edges
             .iter_mut()
-            .map(|e| &mut e.weight)
+            .map(|e| (e.weight.handle, &mut e.weight))
     }
 
     // /// The set of joints as an array.
@@ -202,8 +206,8 @@ impl JointSet {
                 }
 
                 // Wake up the attached bodies.
-                bodies.wake_up(h1);
-                bodies.wake_up(h2);
+                bodies.wake_up(h1, true);
+                bodies.wake_up(h2, true);
             }
 
             if let Some(other) = self.joint_graph.remove_node(deleted_id) {
diff --git a/src/dynamics/rigid_body.rs b/src/dynamics/rigid_body.rs
index a2fcacc..af1fb4a 100644
--- a/src/dynamics/rigid_body.rs
+++ b/src/dynamics/rigid_body.rs
@@ -137,6 +137,15 @@ impl RigidBody {
         crate::utils::inv(self.mass_properties.inv_mass)
     }
 
+    /// The predicted position of this rigid-body.
+    ///
+    /// If this rigid-body is kinematic this value is set by the `set_next_kinematic_position`
+    /// method and is used for estimating the kinematic body velocity at the next timestep.
+    /// For non-kinematic bodies, this value is currently unspecified.
+    pub fn predicted_position(&self) -> &Isometry<f32> {
+        &self.predicted_position
+    }
+
     /// Adds a collider to this rigid-body.
     pub(crate) fn add_collider_internal(&mut self, handle: ColliderHandle, coll: &Collider) {
         let mass_properties = coll
@@ -172,10 +181,13 @@ impl RigidBody {
     }
 
     /// Wakes up this rigid body if it is sleeping.
-    pub fn wake_up(&mut self) {
+    ///
+    /// If `strong` is `true` then it is assured that the rigid-body will
+    /// remain awake during multiple subsequent timesteps.
+    pub fn wake_up(&mut self, strong: bool) {
         self.activation.sleeping = false;
 
-        if self.activation.energy == 0.0 && self.is_dynamic() {
+        if (strong || self.activation.energy == 0.0) && self.is_dynamic() {
             self.activation.energy = self.activation.threshold.abs() * 2.0;
         }
     }
@@ -189,9 +201,18 @@ impl RigidBody {
 
     /// Is this rigid body sleeping?
     pub fn is_sleeping(&self) -> bool {
+        // TODO: should we:
+        // - return false for static bodies.
+        // - return true for non-sleeping dynamic bodies.
+        // - return true only for kinematic bodies with non-zero velocity?
         self.activation.sleeping
     }
 
+    /// Is the velocity of this body not zero?
+    pub fn is_moving(&self) -> bool {
+        !self.linvel.is_zero() || !self.angvel.is_zero()
+    }
+
     fn integrate_velocity(&self, dt: f32) -> Isometry<f32> {
         let com = &self.position * self.mass_properties.local_com;
         let shift = Translation::from(com.coords);
@@ -201,12 +222,17 @@ impl RigidBody {
         self.position = self.integrate_velocity(dt) * self.position;
     }
 
-    /// Sets the position of this rigid body.
+    /// Sets the position and `next_kinematic_position` of this rigid body.
+    ///
+    /// This will teleport the rigid-body to the specified position/orientation,
+    /// completely ignoring any physics rule. If this body is kinematic, this will
+    /// also set the next kinematic position to the same value, effectively
+    /// resetting to zero the next interpolated velocity of the kinematic body.
     pub fn set_position(&mut self, pos: Isometry<f32>) {
         self.position = pos;
 
         // TODO: update the predicted position for dynamic bodies too?
-        if self.is_static() {
+        if self.is_static() || self.is_kinematic() {
             self.predicted_position = pos;
         }
     }
diff --git a/src/dynamics/rigid_body_set.rs b/src/dynamics/rigid_body_set.rs
index 99d6f10..83f1c51 100644
--- a/src/dynamics/rigid_body_set.rs
+++ b/src/dynamics/rigid_body_set.rs
@@ -2,8 +2,8 @@
 use rayon::prelude::*;
 
 use crate::data::arena::Arena;
-use crate::dynamics::{Joint, RigidBody};
-use crate::geometry::{ColliderSet, ContactPair, InteractionGraph};
+use crate::dynamics::{BodyStatus, Joint, JointSet, RigidBody};
+use crate::geometry::{ColliderHandle, ColliderSet, ContactPair, InteractionGraph};
 use crossbeam::channel::{Receiver, Sender};
 use std::ops::{Deref, DerefMut, Index, IndexMut};
 
@@ -128,9 +128,23 @@ impl RigidBodySet {
 
     pub(crate) fn activate(&mut self, handle: RigidBodyHandle) {
         let mut rb = &mut self.bodies[handle];
-        if self.active_dynamic_set.get(rb.active_set_id) != Some(&handle) {
-            rb.active_set_id = self.active_dynamic_set.len();
-            self.active_dynamic_set.push(handle);
+        match rb.body_status {
+            // XXX: this case should only concern the dynamic bodies.
+            // For static bodies we should use the modified_inactive_set, or something
+            // similar. Right now we do this for static bodies as well so the broad-phase
+            // takes them into account the first time they are inserted.
+            BodyStatus::Dynamic | BodyStatus::Static => {
+                if self.active_dynamic_set.get(rb.active_set_id) != Some(&handle) {
+                    rb.active_set_id = self.active_dynamic_set.len();
+                    self.active_dynamic_set.push(handle);
+                }
+            }
+            BodyStatus::Kinematic => {
+                if self.active_kinematic_set.get(rb.active_set_id) != Some(&handle) {
+                    rb.active_set_id = self.active_kinematic_set.len();
+                    self.active_kinematic_set.push(handle);
+                }
+            }
         }
     }
 
@@ -143,13 +157,14 @@ impl RigidBodySet {
     pub fn insert(&mut self, rb: RigidBody) -> RigidBodyHandle {
         let handle = self.bodies.insert(rb);
         let rb = &mut self.bodies[handle];
-        rb.active_set_id = self.active_dynamic_set.len();
 
         if !rb.is_sleeping() && rb.is_dynamic() {
+            rb.active_set_id = self.active_dynamic_set.len();
             self.active_dynamic_set.push(handle);
         }
 
         if rb.is_kinematic() {
+            rb.active_set_id = self.active_kinematic_set.len();
             self.active_kinematic_set.push(handle);
         }
 
@@ -160,29 +175,57 @@ impl RigidBodySet {
         handle
     }
 
-    pub(crate) fn num_islands(&self) -> usize {
-        self.active_islands.len() - 1
-    }
-
-    pub(crate) fn remove_internal(&mut self, handle: RigidBodyHandle) -> Option<RigidBody> {
+    /// Removes a rigid-body, and all its attached colliders and joints, from these sets.
+    pub fn remove(
+        &mut self,
+        handle: RigidBodyHandle,
+        colliders: &mut ColliderSet,
+        joints: &mut JointSet,
+    ) -> Option<RigidBody> {
         let rb = self.bodies.remove(handle)?;
-        // Remove this body from the active dynamic set.
-        if self.active_dynamic_set.get(rb.active_set_id) == Some(&handle) {
-            self.active_dynamic_set.swap_remove(rb.active_set_id);
+        /*
+         * Update active sets.
+         */
+        let mut active_sets = [&mut self.active_kinematic_set, &mut self.active_dynamic_set];
+
+        for active_set in &mut active_sets {
+            if active_set.get(rb.active_set_id) == Some(&handle) {
+                active_set.swap_remove(rb.active_set_id);
 
-            if let Some(replacement) = self.active_dynamic_set.get(rb.active_set_id) {
-                self.bodies[*replacement].active_set_id = rb.active_set_id;
+                if let Some(replacement) = active_set.get(rb.active_set_id) {
+                    self.bodies[*replacement].active_set_id = rb.active_set_id;
+                }
             }
         }
 
+        /*
+         * Remove colliders attached to this rigid-body.
+         */
+        for collider in &rb.colliders {
+            colliders.remove(*collider, self);
+        }
+
+        /*
+         * Remove joints attached to this rigid-body.
+         */
+        joints.remove_rigid_body(rb.joint_graph_index, self);
+
         Some(rb)
     }
 
+    pub(crate) fn num_islands(&self) -> usize {
+        self.active_islands.len() - 1
+    }
+
     /// Forces the specified rigid-body to wake up if it is dynamic.
-    pub fn wake_up(&mut self, handle: RigidBodyHandle) {
+    ///
+    /// If `strong` is `true` then it is assured that the rigid-body will
+    /// remain awake during multiple subsequent timesteps.
+    pub fn wake_up(&mut self, handle: RigidBodyHandle, strong: bool) {
         if let Some(rb) = self.bodies.get_mut(handle) {
+            // TODO: what about kinematic bodies?
             if rb.is_dynamic() {
-                rb.wake_up();
+                rb.wake_up(strong);
 
                 if self.active_dynamic_set.get(rb.active_set_id) != Some(&handle) {
                     rb.active_set_id = self.active_dynamic_set.len();
@@ -214,8 +257,11 @@ impl RigidBodySet {
     ///
     /// 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: usize) -> Option<(&mut RigidBody, RigidBodyHandle)> {
-        self.bodies.get_unknown_gen_mut(i)
+    pub fn get_unknown_gen_mut(&mut self, i: usize) -> Option<(RigidBodyMut, RigidBodyHandle)> {
+        let sender = &self.activation_channel.0;
+        self.bodies
+            .get_unknown_gen_mut(i)
+            .map(|(rb, handle)| (RigidBodyMut::new(handle, rb, sender), handle))
     }
 
     /// Gets the rigid-body with the given handle.
@@ -256,6 +302,16 @@ impl RigidBodySet {
             .map(move |(h, rb)| (h, RigidBodyMut::new(h, rb, sender)))
     }
 
+    /// Iter through all the active kinematic rigid-bodies on this set.
+    pub fn iter_active_kinematic<'a>(
+        &'a self,
+    ) -> impl Iterator<Item = (RigidBodyHandle, &'a RigidBody)> {
+        let bodies: &'a _ = &self.bodies;
+        self.active_kinematic_set
+            .iter()
+            .filter_map(move |h| Some((*h, bodies.get(*h)?)))
+    }
+
     /// Iter through all the active dynamic rigid-bodies on this set.
     pub fn iter_active_dynamic<'a>(
         &'a self,
@@ -425,6 +481,45 @@ impl RigidBodySet {
             }
         }
 
+        // Read all the contacts and push objects touching touching this rigid-body.
+        #[inline(always)]
+        fn push_contacting_colliders(
+            rb: &RigidBody,
+            collid