attempt to reproduce a crash with a more complex example

Cargo.toml

@@ -14,7 +14,7 @@ codegen-units = 1
 #parry2d = { path = "../parry/crates/parry2d" }
 #parry3d = { path = "../parry/crates/parry3d" }
 #rapier2d = { path = "../rapier/crates/rapier2d" }
-#rapier3d = { path = "../rapier/crates/rapier3d" }
+rapier3d = { path = "../rapier/crates/rapier3d" }
 
 #nalgebra = { git = "https://github.com/dimforge/nalgebra", branch = "dev" }
 #parry2d = { git = "https://github.com/dimforge/parry", branch = "master" }

bevy_rapier3d/examples/multi_world3.rs

@@ -13,7 +13,7 @@ fn main() {
         .add_plugins((
             DefaultPlugins,
             RapierPhysicsPlugin::<NoUserData>::default()
-                .with_default_world(RapierContextInitialization::NoAutomaticRapierContext),
+                .with_custom_initialization(RapierContextInitialization::NoAutomaticRapierContext),
             RapierDebugRenderPlugin::default(),
         ))
         .add_systems(

bevy_rapier3d/examples/multi_world_interpolated3.rs

@@ -0,0 +1,99 @@
+use bevy::{input::common_conditions::input_just_pressed, prelude::*};
+use bevy_rapier3d::prelude::*;
+
+const N_WORLDS: usize = 2;
+
+fn main() {
+    App::new()
+        .insert_resource(ClearColor(Color::srgb(
+            0xF9 as f32 / 255.0,
+            0xF9 as f32 / 255.0,
+            0xFF as f32 / 255.0,
+        )))
+        .add_plugins((
+            DefaultPlugins,
+            RapierPhysicsPlugin::<NoUserData>::default()
+                .with_custom_initialization(RapierContextInitialization::NoAutomaticRapierContext),
+            RapierDebugRenderPlugin::default(),
+        ))
+        .insert_resource(TimestepMode::Interpolated {
+            dt: 1.0 / 60.0,
+            time_scale: 1.0,
+            substeps: 2,
+        })
+        .add_systems(
+            Startup,
+            ((create_worlds, setup_physics).chain(), setup_graphics),
+        )
+        .add_systems(
+            Update,
+            change_world, //.run_if(input_just_pressed(KeyCode::KeyC)),
+        )
+        .run();
+}
+
+fn create_worlds(mut commands: Commands) {
+    for i in 0..N_WORLDS {
+        let mut world = commands.spawn(RapierContext::default());
+        if i == 0 {
+            world.insert(DefaultRapierContext);
+        }
+    }
+}
+
+fn setup_graphics(mut commands: Commands) {
+    commands.spawn(Camera3dBundle {
+        transform: Transform::from_xyz(0.0, 3.0, -10.0)
+            .looking_at(Vec3::new(0.0, 0.0, 0.0), Vec3::Y),
+        ..Default::default()
+    });
+}
+
+fn change_world(
+    query_context: Query<Entity, With<DefaultRapierContext>>,
+    q_other_ctx: Query<Entity, (With<RapierContext>, Without<DefaultRapierContext>)>,
+    mut query_links: Query<&mut RapierContextEntityLink>,
+) {
+    let default_context = query_context.single();
+    for mut link in query_links.iter_mut() {
+        if link.0 == default_context {
+            link.0 = q_other_ctx.single();
+            continue;
+        }
+        link.0 = default_context;
+    }
+}
+
+pub fn setup_physics(mut commands: Commands) {
+    /*
+     * Create the cube
+     */
+
+    let color = [
+        Hsla::hsl(220.0, 1.0, 0.3),
+        Hsla::hsl(180.0, 1.0, 0.3),
+        Hsla::hsl(260.0, 1.0, 0.7),
+    ][0 % 3];
+
+    commands.spawn((
+        TransformBundle::from(Transform::from_xyz(0.0, 0.0, 0.0)),
+        RigidBody::Dynamic,
+        Collider::cuboid(0.5, 0.5, 0.5),
+        ColliderDebugColor(color),
+        ActiveEvents::all(),
+    ));
+
+    /*
+     * Ground
+     */
+    let color = Hsla::hsl(260.0, 1.0, 0.7);
+    let ground_size = 5.1;
+    let ground_height = 0.1;
+    let starting_y = -0.5 - ground_height;
+
+    commands.spawn((
+        TransformBundle::from(Transform::from_xyz(0.0, starting_y, 0.0)),
+        Collider::cuboid(ground_size, ground_height, ground_size),
+        ColliderDebugColor(color),
+    ));
+}

src/pipeline/events.rs

@@ -68,7 +68,9 @@ impl<'a> EventQueue<'a> {
             .get(handle)
             .map(|co| Entity::from_bits(co.user_data as u64))
             .or_else(|| self.deleted_colliders.get(&handle).copied())
-            .expect("Internal error: entity not found for collision event.")
+            .unwrap_or_else(|| {
+                panic!("Internal error: entity not found for collision event with collider handle: {handle:?}.")
+            })
     }
 }
 

src/plugin/context/mod.rs

@@ -289,6 +289,7 @@ impl RapierContext {
                     substep_integration_parameters.dt = dt / (substeps as Real) * time_scale;
 
                     for _ in 0..substeps {
+                        dbg!("execute step");
                         self.pipeline.step(
                             &gravity.into(),
                             &substep_integration_parameters,

src/plugin/plugin.rs

@@ -47,10 +47,8 @@ where
         self
     }
 
-    /// Specifies a default world initialization strategy.
-    ///
-    /// The default is to initialize a [`RapierContext`] with a length unit of 1.
-    pub fn with_default_world(
+    /// Specifies an initialization strategy when the [`App`] starts.
+    pub fn with_custom_initialization(
         mut self,
         default_world_initialization: RapierContextInitialization,
     ) -> Self {
@@ -110,6 +108,7 @@ where
                 systems::on_add_entity_with_parent,
                 systems::on_change_world,
                 systems::sync_removals,
+                apply_deferred,
                 #[cfg(all(feature = "dim3", feature = "async-collider"))]
                 systems::init_async_scene_colliders,
                 #[cfg(all(feature = "dim3", feature = "async-collider"))]
@@ -206,16 +205,15 @@ where
             .register_type::<RapierConfiguration>()
             .register_type::<SimulationToRenderTime>()
             .register_type::<DefaultRapierContext>()
-            .register_type::<RapierContextInitialization>()
-            .register_type::<ColliderDebugColor>();
+            .register_type::<RapierContextInitialization>();
 
         app.insert_resource(Events::<CollisionEvent>::default())
             .insert_resource(Events::<ContactForceEvent>::default())
             .insert_resource(Events::<MassModifiedEvent>::default());
         let default_world_init = app.world().get_resource::<RapierContextInitialization>();
         if let Some(world_init) = default_world_init {
             warn!("RapierPhysicsPlugin added but a `RapierContextInitialization` resource was already existing.\
-            This might overwrite previous configuration made via `RapierPhysicsPlugin::with_default_world`\
+            This will overwrite previous configuration made via `RapierPhysicsPlugin::with_custom_initialization`\
             or `RapierPhysicsPlugin::with_length_unit`.
             The following resource will be used: {:?}", world_init);
         } else {

src/plugin/systems/collider.rs

@@ -384,6 +384,7 @@ pub fn init_colliders(
         let Some(context_entity) = context_entity else {
             continue;
         };
+        println!("init collider {entity} for world {context_entity}");
 
         let config = config.get(context_entity).unwrap_or_else(|_| {
             panic!("Failed to retrieve `RapierConfiguration` on entity {context_entity}.")

src/plugin/systems/mod.rs

@@ -28,6 +28,7 @@ use bevy::prelude::*;
 /// for scene queries.
 pub fn step_simulation<Hooks>(
     mut context: Query<(
+        Entity,
         &mut RapierContext,
         &RapierConfiguration,
         &mut SimulationToRenderTime,
@@ -44,10 +45,12 @@ pub fn step_simulation<Hooks>(
 {
     let hooks_adapter = BevyPhysicsHooksAdapter::new(hooks.into_inner());
 
-    for (mut context, config, mut sim_to_render_time) in context.iter_mut() {
+    for (entity, mut context, config, mut sim_to_render_time) in context.iter_mut() {
         let context = &mut *context;
 
         if config.physics_pipeline_active {
+            println!("step {entity}");
+            //println!("step {:?}", context.colliders);
             context.step_simulation(
                 config.gravity,
                 *timestep_mode,
@@ -57,7 +60,9 @@ pub fn step_simulation<Hooks>(
                 &mut sim_to_render_time,
                 Some(&mut interpolation_query),
             );
-            context.deleted_colliders.clear();
+            println!("clear");
+            // That's the offending line ! This should be within `step_simulation` only if we actually step.
+            // context.deleted_colliders.clear();
         } else {
             context.propagate_modified_body_positions_to_colliders();
         }