Merge branch 'master' into split_geom

# Conflicts:
#	examples2d/sensor2.rs
#	examples3d/sensor3.rs
#	src/dynamics/integration_parameters.rs
#	src/dynamics/solver/parallel_island_solver.rs
#	src/dynamics/solver/velocity_constraint.rs
#	src/dynamics/solver/velocity_ground_constraint.rs
#	src_testbed/nphysics_backend.rs
#	src_testbed/physx_backend.rs
#	src_testbed/testbed.rs

24 files changed, 359 insertions, 356 deletions

diff --git a/.github/workflows/rapier-ci-bench.yml b/.github/workflows/rapier-ci-bench.yml
index aa6e6ca..29653e8 100644
--- a/.github/workflows/rapier-ci-bench.yml
+++ b/.github/workflows/rapier-ci-bench.yml
@@ -3,7 +3,7 @@ name: Rapier CI bench
 on:
   push:
     branches: [ master ]
-  pull_request:
+  pull_request_target:
     branches: [ master ]
   workflow_dispatch:
 
@@ -14,21 +14,23 @@ jobs:
       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_REPO: ${{ github.event.pull_request.head.repo.clone_url }}
       BENCHBOT_TARGET_COMMIT: ${{ github.event.pull_request.head.sha }}
       BENCHBOT_SHA: ${{ github.sha }}
-      BENCHBOT_HEAD_REF: ${{github.head_ref}}
+      BENCHBOT_HEAD_REF: ${{ github.head_ref }}
       BENCHBOT_OTHER_BACKENDS: false
     runs-on: ubuntu-latest
     steps:
-      - name: Find commit SHA
-        if: github.ref == 'refs/heads/master'
+      - name: Set env on master
+        if: github.head_ref == ''
         run: |
           echo "BENCHBOT_TARGET_COMMIT=$BENCHBOT_SHA" >> $GITHUB_ENV
+          echo "BENCHBOT_TARGET_REPO=https://github.com/dimforge/rapier" >> $GITHUB_ENV
+          echo "BENCHBOT_HEAD_REF=master" >> $GITHUB_ENV
           echo "BENCHBOT_OTHER_BACKENDS=true" >> $GITHUB_ENV
       - name: Send 3D bench message
         shell: bash
         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
-            -d'{"properties":{},"routing_key":"benchmark","payload":"{ \"repository\":\"https://github.com/'$BENCHBOT_TARGET_REPO'\", \"branch\":\"'$GITHUB_REF'\", \"commit\":\"'$BENCHBOT_TARGET_COMMIT'\", \"other_backends\":'$BENCHBOT_OTHER_BACKENDS' }","payload_encoding":"string"}'
\ No newline at end of file
+            -d'{"properties":{},"routing_key":"benchmark","payload":"{ \"repository\":\"'$BENCHBOT_TARGET_REPO'\", \"branch\":\"'$BENCHBOT_HEAD_REF'\", \"commit\":\"'$BENCHBOT_TARGET_COMMIT'\", \"other_backends\":'$BENCHBOT_OTHER_BACKENDS' }","payload_encoding":"string"}'
\ No newline at end of file
diff --git a/examples2d/add_remove2.rs b/examples2d/add_remove2.rs
index a3d223d..0aeffbe 100644
--- a/examples2d/add_remove2.rs
+++ b/examples2d/add_remove2.rs
@@ -10,7 +10,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let rad = 0.5;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0)
             .build();
@@ -19,7 +19,10 @@ pub fn init_world(testbed: &mut Testbed) {
         physics
             .colliders
             .insert(collider, handle, &mut physics.bodies);
-        graphics.add(window, handle, &physics.bodies, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add(*window, handle, &physics.bodies, &physics.colliders);
+        }
 
         let to_remove: Vec<_> = physics
             .bodies
@@ -31,7 +34,10 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .bodies
                 .remove(handle, &mut physics.colliders, &mut physics.joints);
-            graphics.remove_body_nodes(window, handle);
+
+            if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+                graphics.remove_body_nodes(*window, handle);
+            }
         }
     });
 
diff --git a/examples2d/platform2.rs b/examples2d/platform2.rs
index 20b2e59..afd4d64 100644
--- a/examples2d/platform2.rs
+++ b/examples2d/platform2.rs
@@ -60,13 +60,13 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Setup a callback to control the platform.
      */
-    testbed.add_callback(move |_, physics, _, _, time| {
+    testbed.add_callback(move |_, _, physics, _, run_state| {
         let platform = physics.bodies.get_mut(platform_handle).unwrap();
         let mut next_pos = *platform.position();
 
         let dt = 0.016;
-        next_pos.translation.vector.y += (time * 5.0).sin() * dt;
-        next_pos.translation.vector.x += time.sin() * 5.0 * dt;
+        next_pos.translation.vector.y += (run_state.time * 5.0).sin() * dt;
+        next_pos.translation.vector.x += run_state.time.sin() * 5.0 * dt;
 
         if next_pos.translation.vector.x >= rad * 10.0 {
             next_pos.translation.vector.x -= dt;
diff --git a/examples2d/sensor2.rs b/examples2d/sensor2.rs
index 6649a43..e53abe3 100644
--- a/examples2d/sensor2.rs
+++ b/examples2d/sensor2.rs
@@ -69,7 +69,7 @@ pub fn init_world(testbed: &mut Testbed) {
     testbed.set_body_color(sensor_handle, Point3::new(0.5, 1.0, 1.0));
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |_, physics, events, graphics, _| {
+    testbed.add_callback(move |_, mut graphics, physics, events, _| {
         while let Ok(prox) = events.intersection_events.try_recv() {
             let color = if prox.intersecting {
                 Point3::new(1.0, 1.0, 0.0)
@@ -79,12 +79,13 @@ pub fn init_world(testbed: &mut Testbed) {
 
             let parent_handle1 = physics.colliders.get(prox.collider1).unwrap().parent();
             let parent_handle2 = physics.colliders.get(prox.collider2).unwrap().parent();
-
-            if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
-                graphics.set_body_color(parent_handle1, color);
-            }
-            if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
-                graphics.set_body_color(parent_handle2, color);
+            if let Some(graphics) = &mut graphics {
+                if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
+                    graphics.set_body_color(parent_handle1, color);
+                }
+                if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
+                    graphics.set_body_color(parent_handle2, color);
+                }
             }
         }
     });
diff --git a/examples3d/debug_add_remove_collider3.rs b/examples3d/debug_add_remove_collider3.rs
index a42dc97..f353162 100644
--- a/examples3d/debug_add_remove_collider3.rs
+++ b/examples3d/debug_add_remove_collider3.rs
@@ -34,7 +34,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let collider = ColliderBuilder::ball(ball_rad).density(100.0).build();
     colliders.insert(collider, ball_handle, &mut bodies);
 
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         // Remove then re-add the ground collider.
         let coll = physics
             .colliders
@@ -43,7 +43,10 @@ pub fn init_world(testbed: &mut Testbed) {
         ground_collider_handle = physics
             .colliders
             .insert(coll, ground_handle, &mut physics.bodies);
-        graphics.add_collider(window, ground_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, ground_collider_handle, &physics.colliders);
+        }
     });
 
     /*
diff --git a/examples3d/debug_dynamic_collider_add3.rs b/examples3d/debug_dynamic_collider_add3.rs
index a71e95e..bd7205e 100644
--- a/examples3d/debug_dynamic_collider_add3.rs
+++ b/examples3d/debug_dynamic_collider_add3.rs
@@ -45,7 +45,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut extra_colliders = Vec::new();
     let snapped_frame = 51;
 
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         step += 1;
 
         // Add a bigger ball collider
@@ -56,7 +56,11 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .colliders
                 .insert(collider, ball_handle, &mut physics.bodies);
-        graphics.add_collider(window, new_ball_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, new_ball_collider_handle, &physics.colliders);
+        }
+
         extra_colliders.push(new_ball_collider_handle);
 
         // Snap the ball velocity or restore it.
@@ -95,7 +99,11 @@ pub fn init_world(testbed: &mut Testbed) {
             physics
                 .colliders
                 .insert(coll, ground_handle, &mut physics.bodies);
-        graphics.add_collider(window, new_ground_collider_handle, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add_collider(window, new_ground_collider_handle, &physics.colliders);
+        }
+
         extra_colliders.push(new_ground_collider_handle);
     });
 
diff --git a/examples3d/debug_rollback3.rs b/examples3d/debug_rollback3.rs
index 19f9474..27b27cf 100644
--- a/examples3d/debug_rollback3.rs
+++ b/examples3d/debug_rollback3.rs
@@ -44,7 +44,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut step = 0;
     let snapped_frame = 51;
 
-    testbed.add_callback(move |_, physics, _, _, _| {
+    testbed.add_callback(move |_, _, physics, _, _| {
         step += 1;
 
         // Snap the ball velocity or restore it.
diff --git a/examples3d/fountain3.rs b/examples3d/fountain3.rs
index fafa988..5acc2e8 100644
--- a/examples3d/fountain3.rs
+++ b/examples3d/fountain3.rs
@@ -26,7 +26,7 @@ pub fn init_world(testbed: &mut Testbed) {
     let mut k = 0;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |window, physics, _, graphics, _| {
+    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
         k += 1;
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0, 0.0)
@@ -41,7 +41,10 @@ pub fn init_world(testbed: &mut Testbed) {
         physics
             .colliders
             .insert(collider, handle, &mut physics.bodies);
-        graphics.add(window, handle, &physics.bodies, &physics.colliders);
+
+        if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+            graphics.add(window, handle, &physics.bodies, &physics.colliders);
+        }
 
         if physics.bodies.len() > MAX_NUMBER_OF_BODIES {
             let mut to_remove: Vec<_> = physics
@@ -67,7 +70,10 @@ pub fn init_world(testbed: &mut Testbed) {
                 physics
                     .narrow_phase
                     .maintain(&mut physics.colliders, &mut physics.bodies);
-                graphics.remove_body_nodes(window, *handle);
+
+                if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+                    graphics.remove_body_nodes(window, *handle);
+                }
             }
         }
     });
diff --git a/examples3d/platform3.rs b/examples3d/platform3.rs
index 0975f39..7b5c986 100644
--- a/examples3d/platform3.rs
+++ b/examples3d/platform3.rs
@@ -65,7 +65,7 @@ pub fn init_world(testbed: &mut Testbed) {
      * Setup a callback to control the platform.
      */
     let mut count = 0;
-    testbed.add_callback(move |_, physics, _, _, time| {
+    testbed.add_callback(move |_, _, physics, _, run_state| {
         count += 1;
         if count % 100 > 50 {
             return;
@@ -75,8 +75,8 @@ pub fn init_world(testbed: &mut Testbed) {
             let mut next_pos = *platform.position();
 
             let dt = 0.016;
-            next_pos.translation.vector.y += (time * 5.0).sin() * dt;
-            next_pos.translation.vector.z += time.sin() * 5.0 * dt;
+            next_pos.translation.vector.y += (run_state.time * 5.0).sin() * dt;
+            next_pos.translation.vector.z += run_state.time.sin() * 5.0 * dt;
 
             if next_pos.translation.vector.z >= rad * 10.0 {
                 next_pos.translation.vector.z -= dt;
diff --git a/examples3d/sensor3.rs b/examples3d/sensor3.rs
index 234eaf3..641e93d 100644
--- a/examples3d/sensor3.rs
+++ b/examples3d/sensor3.rs
@@ -73,7 +73,7 @@ pub fn init_world(testbed: &mut Testbed) {
     testbed.set_body_color(sensor_handle, Point3::new(0.5, 1.0, 1.0));
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |_, physics, events, graphics, _| {
+    testbed.add_callback(move |_, mut graphics, physics, events, _| {
         while let Ok(prox) = events.intersection_events.try_recv() {
             let color = if prox.intersecting {
                 Point3::new(1.0, 1.0, 0.0)
@@ -84,11 +84,13 @@ pub fn init_world(testbed: &mut Testbed) {
             let parent_handle1 = physics.colliders.get(prox.collider1).unwrap().parent();
             let parent_handle2 = physics.colliders.get(prox.collider2).unwrap().parent();
 
-            if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
-                graphics.set_body_color(parent_handle1, color);
-            }
-            if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
-                graphics.set_body_color(parent_handle2, color);
+            if let Some(graphics) = &mut graphics {
+                if parent_handle1 != ground_handle && parent_handle1 != sensor_handle {
+                    graphics.set_body_color(parent_handle1, color);
+                }
+                if parent_handle2 != ground_handle && parent_handle2 != sensor_handle {
+                    graphics.set_body_color(parent_handle2, color);
+                }
             }
         }
     });
diff --git a/src/dynamics/integration_parameters.rs b/src/dynamics/integration_parameters.rs
index 706fb3f..0d4d3b6 100644
--- a/src/dynamics/integration_parameters.rs
+++ b/src/dynamics/integration_parameters.rs
@@ -5,9 +5,8 @@ use crate::math::Real;
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
 pub struct IntegrationParameters {
     /// The timestep length (default: `1.0 / 60.0`)
-    dt: Real,
-    /// The inverse of `dt`.
-    inv_dt: Real,
+    pub dt: Real,
+
     //    /// If `true` and if rapier is compiled with the `parallel` feature, this will enable rayon-based multithreading (default: `true`).
     //    ///
     //    /// This parameter is ignored if rapier is not compiled with is `parallel` feature.
@@ -31,7 +30,7 @@ pub struct IntegrationParameters {
     /// Contacts at points where the involved bodies have a relative
     /// velocity smaller than this threshold wont be affected by the restitution force (default: `1.0`).
     pub restitution_velocity_threshold: Real,
-    /// Amount of penetration the engine wont attempt to correct (default: `0.001m`).
+    /// Amount of penetration the engine wont attempt to correct (default: `0.005m`).
     pub allowed_linear_error: Real,
     /// The maximal distance separating two objects that will generate predictive contacts (default: `0.002`).
     pub prediction_distance: Real,
@@ -89,6 +88,7 @@ pub struct IntegrationParameters {
 
 impl IntegrationParameters {
     /// Creates a set of integration parameters with the given values.
+    #[deprecated = "Use `IntegrationParameters { dt: 60.0, ..Default::default() }` instead"]
     pub fn new(
         dt: Real,
         //        multithreading_enabled: bool,
@@ -112,7 +112,6 @@ impl IntegrationParameters {
     ) -> Self {
         IntegrationParameters {
             dt,
-            inv_dt: if dt == 0.0 { 0.0 } else { 1.0 / dt },
             //            multithreading_enabled,
             erp,
             joint_erp,
@@ -142,30 +141,29 @@ impl IntegrationParameters {
 
     /// The current time-stepping length.
     #[inline(always)]
+    #[deprecated = "You can just read the `IntegrationParams::dt` value directly"]
     pub fn dt(&self) -> Real {
         self.dt
     }
 
-    /// The inverse of the time-stepping length.
+    /// The inverse of the time-stepping length, i.e. the steps per seconds (Hz).
     ///
     /// This is zero if `self.dt` is zero.
     #[inline(always)]
     pub fn inv_dt(&self) -> Real {
-        self.inv_dt
+        if self.dt == 0.0 {
+            0.0
+        } else {
+            1.0 / self.dt
+        }
     }
 
     /// Sets the time-stepping length.
-    ///
-    /// This automatically recompute `self.inv_dt`.
     #[inline]
+    #[deprecated = "You can just set the `IntegrationParams::dt` value directly"]
     pub fn set_dt(&mut self, dt: Real) {
         assert!(dt >= 0.0, "The time-stepping length cannot be negative.");
         self.dt = dt;
-        if dt == 0.0 {
-            self.inv_dt = 0.0
-        } else {
-            self.inv_dt = 1.0 / dt
-        }
     }
 
     /// Sets the inverse time-stepping length (i.e. the frequency).
@@ -173,7 +171,6 @@ impl IntegrationParameters {
     /// This automatically recompute `self.dt`.
     #[inline]
     pub fn set_inv_dt(&mut self, inv_dt: Real) {
-        self.inv_dt = inv_dt;
         if inv_dt == 0.0 {
             self.dt = 0.0
         } else {
@@ -184,26 +181,32 @@ impl IntegrationParameters {
 
 impl Default for IntegrationParameters {
     fn default() -> Self {
-        Self::new(
-            1.0 / 60.0,
-            //            true,
-            0.2,
-            0.2,
-            1.0,
-            1.0,
-            0.005,
-            0.001,
-            0.2,
-            0.2,
-            0.002,
-            0.2,
-            4,
-            1,
-            10,
-            1,
-            false,
-            false,
-            false,
-        )
+        Self {
+            dt: 1.0 / 60.0,
+            //        multithreading_enabled:             true,
+            return_after_ccd_substep: false,
+            erp: 0.2,
+            joint_erp: 0.2,
+            warmstart_coeff: 1.0,
+            restitution_velocity_threshold: 1.0,
+            allowed_linear_error: 0.005,
+            prediction_distance: 0.002,
+            allowed_angular_error: 0.001,
+            max_linear_correction: 0.2,
+            max_angular_correction: 0.2,
+            max_stabilization_multiplier: 0.2,
+            max_velocity_iterations: 4,
+            max_position_iterations: 1,
+            // FIXME: what is the optimal value for min_island_size?
+            // It should not be too big so that we don't end up with
+            // huge islands that don't fit in cache.
+            // However we don't want it to be too small and end up with
+            // tons of islands, reducing SIMD parallelism opportunities.
+            min_island_size: 128,
+            max_ccd_position_iterations: 10,
+            max_ccd_substeps: 1,
+            multiple_ccd_substep_sensor_events_enabled: false,
+            ccd_on_penetration_enabled: false,
+        }
     }
 }
diff --git a/src/dynamics/solver/island_solver.rs b/src/dynamics/solver/island_solver.rs
index 46d6b75..deed8c2 100644
--- a/src/dynamics/solver/island_solver.rs
+++ b/src/dynamics/solver/island_solver.rs
@@ -57,8 +57,7 @@ impl IslandSolver {
         }
 
         counters.solver.velocity_update_time.resume();
-        bodies
-            .foreach_active_island_body_mut_internal(island_id, |_, rb| rb.integrate(params.dt()));
+        bodies.foreach_active_island_body_mut_internal(island_id, |_, rb| rb.integrate(params.dt));
         counters.solver.velocity_update_time.pause();
 
         if manifold_indices.len() != 0 || joint_indices.len() != 0 {
diff --git a/src/dynamics/solver/parallel_island_solver.rs b/src/dynamics/solver/parallel_island_solver.rs
index 389b6e6..24435db 100644
--- a/src/dynamics/solver/parallel_island_solver.rs
+++ b/src/dynamics/solver/parallel_island_solver.rs
@@ -251,7 +251,7 @@ impl ParallelIslandSolver {
                         let dvel = mj_lambdas[rb.active_set_offset];
                         rb.linvel += dvel.linear;
                         rb.angvel += rb.effective_world_inv_inertia_sqrt.transform_vector(dvel.angular);
-                        rb.integrate(params.dt());
+                        rb.integrate(params.dt));
                         positions[rb.active_set_offset] = rb.position;
                     }
                 }
diff --git a/src/dynamics/solver/velocity_constraint.rs b/src/dynamics/solver/velocity_constraint.rs
index c2aa6f5..9d75830 100644
--- a/src/dynamics/solver/velocity_constraint.rs
+++ b/src/dynamics/solver/velocity_constraint.rs
@@ -144,6 +144,7 @@ impl VelocityConstraint {
         out_constraints: &mut Vec<AnyVelocityConstraint>,
         push: bool,
     ) {
+        let inv_dt = params.inv_dt();
         let rb1 = &bodies[manifold.data.body_pair.body1];
         let rb2 = &bodies[manifold.data.body_pair.body2];
         let mj_lambda1 = rb1.active_set_offset;
@@ -244,7 +245,7 @@ impl VelocityConstraint {
                         rhs += manifold_point.restitution * rhs
                     }
 
-                    rhs += manifold_point.dist.max(0.0) * params.inv_dt();
+                    rhs += manifold_point.dist.max(0.0) * inv_dt;
 
                     let impulse = manifold_point.data.impulse * warmstart_coeff;
 
diff --git a/src/dynamics/solver/velocity_ground_constraint.rs b/src/dynamics/solver/velocity_ground_constraint.rs
index 7ea4fbb..49bb465 100644
--- a/src/dynamics/solver/velocity_ground_constraint.rs
+++ b/src/dynamics/solver/velocity_ground_constraint.rs
@@ -63,6 +63,7 @@ impl VelocityGroundConstraint {
         out_constraints: &mut Vec<AnyVelocityConstraint>,
         push: bool,
     ) {
+        let inv_dt = params.inv_dt();
         let mut rb1 = &bodies[manifold.data.body_pair.body1];
         let mut rb2 = &bodies[manifold.data.body_pair.body2];
         let flipped = !rb2.is_dynamic();
@@ -159,7 +160,7 @@ impl VelocityGroundConstraint {
                         rhs += manifold_point.restitution * rhs
                     }
 
-                    rhs += manifold_point.dist.max(0.0) * params.inv_dt();
+                    rhs += manifold_point.dist.max(0.0) * inv_dt;
 
                     let impulse = manifold_points[k].data.impulse * warmstart_coeff;
 
diff --git a/src/pipeline/physics_pipeline.rs b/src/pipeline/physics_pipeline.rs
index 718dd10..d59a534 100644
--- a/src/pipeline/physics_pipeline.rs
+++ b/src/pipeline/physics_pipeline.rs
@@ -154,7 +154,7 @@ impl PhysicsPipeline {
         self.counters.stages.update_time.start();
         bodies.foreach_active_dynamic_body_mut_internal(|_, b| {
             b.update_world_mass_properties();
-            b.integrate_accelerations(integration_parameters.dt(), *gravity)
+            b.integrate_accelerations(integration_parameters.dt, *gravity)
         });
         self.counters.stages.update_time.pause();
 
@@ -233,7 +233,7 @@ impl PhysicsPipeline {
                 rb.linvel = na::zero();
                 rb.angvel = na::zero();
             } else {
-                rb.update_predicted_position(integration_parameters.dt());
+                rb.update_predicted_position(integration_parameters.dt);
             }
 
             rb.update_colliders_positions(colliders);
@@ -330,6 +330,7 @@ mod test {
         );
     }
 
+    #[cfg(feature = "serde")]
     #[test]
     fn rigid_body_removal_snapshot_handle_determinism() {
         let mut colliders = ColliderSet::new();
diff --git a/src_testbed/box2d_backend.rs b/src_testbed/box2d_backend.rs
index 2d4ef29..29fd4fa 100644
--- a/src_testbed/box2d_backend.rs
+++ b/src_testbed/box2d_backend.rs
@@ -219,7 +219,7 @@ impl Box2dWorld {
 
         counters.step_started();
         self.world.step(
-            params.dt(),
+            params.dt,
             params.max_velocity_iterations as i32,
             params.max_position_iterations as i32,
         );
diff --git a/src_testbed/harness/mod.rs b/src_testbed/harness/mod.rs
index c95a722..413ef52 100644
--- a/src_testbed/harness/mod.rs
+++ b/src_testbed/harness/mod.rs
@@ -1,4 +1,8 @@
-use crate::physics::{PhysicsEvents, PhysicsState};
+use crate::{
+    physics::{PhysicsEvents, PhysicsState},
+    GraphicsManager,
+};
+use kiss3d::window::Window;
 use plugin::HarnessPlugin;
 use rapier::dynamics::{IntegrationParameters, JointSet, RigidBodySet};
 use rapier::geometry::{BroadPhase, ColliderSet, NarrowPhase};
@@ -7,24 +11,58 @@ use rapier::pipeline::{ChannelEventCollector, PhysicsPipeline, QueryPipeline};
 
 pub mod plugin;
 
-pub struct HarnessState {
+pub struct RunState {
     #[cfg(feature = "parallel")]
     pub thread_pool: rapier::rayon::ThreadPool,
+    #[cfg(feature = "parallel")]
+    pub num_threads: usize,
     pub timestep_id: usize,
+    pub time: f32,
+}
+
+impl RunState {
+    pub fn new() -> Self {
+        #[cfg(feature = "parallel")]
+        let num_threads = num_cpus::get_physical();
+
+        #[cfg(feature = "parallel")]
+        let thread_pool = rapier::rayon::ThreadPoolBuilder::new()
+            .num_threads(num_threads)
+            .build()
+            .unwrap();
+
+        Self {
+            #[cfg(feature = "parallel")]
+            thread_pool: thread_pool,
+            #[cfg(feature = "parallel")]
+            num_threads,
+            timestep_id: 0,
+            time: 0.0,
+        }
+    }
 }
 
 pub struct Harness {
-    physics: PhysicsState,
+    pub physics: PhysicsState,
     max_steps: usize,
     callbacks: Callbacks,
     plugins: Vec<Box<dyn HarnessPlugin>>,
-    time: f32,
     events: PhysicsEvents,
     event_handler: ChannelEventCollector,
-    pub state: HarnessState,
+    pub state: RunState,
 }
 
-type Callbacks = Vec<Box<dyn FnMut(&mut PhysicsState, &PhysicsEvents, &HarnessState, f32)>>;
+type Callbacks = Vec<
+    Box<
+        dyn FnMut(
+            Option<&mut Window>,
+            Option<&mut GraphicsManager>,
+            &mut PhysicsState,
+            &PhysicsEvents,
+            &RunState,
+        ),
+    >,
+>;
 
 #[allow(dead_code)]
 impl Harness {
@@ -46,18 +84,13 @@ impl Harness {
             intersection_events: proximity_channel.1,
         };
         let physics = PhysicsState::new();
-        let state = HarnessState {
-            #[cfg(feature = "parallel")]
-            thread_pool,
-            timestep_id: 0,
-        };
+        let state = RunState::new();
 
         Self {
             physics,
             max_steps: 1000,
             callbacks: Vec::new(),
             plugins: Vec::new(),
-            time: 0.0,
             events,
             event_handler,
             state,
@@ -101,7 +134,6 @@ impl Harness {
         self.physics.joints = joints;
         self.physics.broad_phase = BroadPhase::new();
         self.physics.narrow_phase = NarrowPhase::new();
-        self.time = 0.0;
         self.state.timestep_id = 0;
         self.physics.query_pipeline = QueryPipeline::new();
         self.physics.pipeline = PhysicsPipeline::new();
@@ -113,7 +145,13 @@ impl Harness {
     }
 
     pub fn add_callback<
-        F: FnMut(&mut PhysicsState, &PhysicsEvents, &HarnessState, f32) + 'static,
+        F: FnMut(
+                Option<&mut Window>,
+                Option<&mut GraphicsManager>,
+                &mut PhysicsState,
+                &PhysicsEvents,
+                &RunState,
+            ) + 'static,
     >(
         &mut self,
         callback: F,
@@ -122,6 +160,14 @@ impl Harness {
     }
 
     pub fn step(&mut self) {
+        self.step_with_graphics(None, None);
+    }
+
+    pub fn step_with_graphics(
+        &mut self,
+        window: Option<&mut Window>,
+        graphics: Option<&mut GraphicsManager>,
+    ) {
         #[cfg(feature = "parallel")]
         {
             let physics = &mut self.physics;
@@ -161,26 +207,44 @@ impl Harness {
             .update(&self.physics.bodies, &self.physics.colliders);
 
         for plugin in &mut self.plugins {
-            plugin.step(&mut self.physics)
+            plugin.step(&mut self.physics, &self.state)
         }
 
-        for f in &mut self.callbacks {
-            f(&mut self.physics, &self.events, &self.state, self.time)
+        // FIXME: This assumes either window & graphics are Some, or they are all None
+        // this is required as we cannot pass Option<&mut Window> & Option<&mut GraphicsManager directly in a loop
+        // there must be a better way of doing this?
+        match (window, graphics) {
+            (Some(window), Some(graphics)) =>