Allow customizing the schedule with FixedUpdate

CHANGELOG.md

@@ -6,6 +6,8 @@
     `TypedShape` or `SharedShape`. The `From` trait has also been implemented accordingly.
 - Implement `Copy` for `ColliderView` and all the other non-mut shape views.
 - Add `RapierContext::rigid_body_colliders` to retrieve all collider entities attached to this rigid-body.
+- Add `RapierPhysicsPlugin::in_fixed_schedule`/`::in_schedude` to add rapier’s systems to a fixed/custom
+  schedule.
 
 ## 0.22.0 (10 July 2023)
 ### Modified

src/plugin/plugin.rs

@@ -2,7 +2,11 @@ use crate::pipeline::{CollisionEvent, ContactForceEvent};
 use crate::plugin::configuration::SimulationToRenderTime;
 use crate::plugin::{systems, RapierConfiguration, RapierContext};
 use crate::prelude::*;
-use bevy::ecs::{event::Events, schedule::SystemConfigs, system::SystemParamItem};
+use bevy::ecs::{
+    event::Events,
+    schedule::{ScheduleLabel, SystemConfigs},
+    system::SystemParamItem,
+};
 use bevy::{prelude::*, transform::TransformSystem};
 use std::marker::PhantomData;
 
@@ -14,6 +18,7 @@ pub type NoUserData = ();
 /// This will automatically setup all the resources needed to run a physics simulation with the
 /// Rapier physics engine.
 pub struct RapierPhysicsPlugin<PhysicsHooks = ()> {
+    schedule: Box<dyn ScheduleLabel>,
     physics_scale: f32,
     default_system_setup: bool,
     _phantom: PhantomData<PhysicsHooks>,
@@ -52,10 +57,21 @@ where
         Self {
             physics_scale: pixels_per_meter,
             default_system_setup: true,
-            _phantom: PhantomData,
+            ..default()
         }
     }
 
+    /// Adds the physics systems to the `FixedUpdate` schedule rather than `PostUpdate`.
+    pub fn in_fixed_schedule(self) -> Self {
+        self.in_schedule(FixedUpdate)
+    }
+
+    /// Adds the physics systems to the provided schedule rather than `PostUpdate`.
+    pub fn in_schedule(mut self, schedule: impl ScheduleLabel) -> Self {
+        self.schedule = Box::new(schedule);
+        self
+    }
+
     /// Provided for use when staging systems outside of this plugin using
     /// [`with_system_setup(false)`](Self::with_system_setup).
     /// See [`PhysicsSet`] for a description of these systems.
@@ -121,6 +137,7 @@ pub struct RapierTransformPropagateSet;
 impl<PhysicsHooksSystemParam> Default for RapierPhysicsPlugin<PhysicsHooksSystemParam> {
     fn default() -> Self {
         Self {
+            schedule: Box::new(PostUpdate),
             physics_scale: 1.0,
             default_system_setup: true,
             _phantom: PhantomData,
@@ -192,7 +209,7 @@ where
         // Add each set as necessary
         if self.default_system_setup {
             app.configure_sets(
-                PostUpdate,
+                self.schedule.clone(),
                 (
                     PhysicsSet::SyncBackend,
                     PhysicsSet::SyncBackendFlush,
@@ -203,8 +220,11 @@ where
                     .before(TransformSystem::TransformPropagate),
             );
 
+            // These *must* be in the main schedule currently so that they do not miss events.
+            app.add_systems(PostUpdate, (systems::sync_removals,));
+
             app.add_systems(
-                PostUpdate,
+                self.schedule.clone(),
                 (
                     Self::get_systems(PhysicsSet::SyncBackend).in_set(PhysicsSet::SyncBackend),
                     Self::get_systems(PhysicsSet::SyncBackendFlush)
@@ -214,6 +234,17 @@ where
                     Self::get_systems(PhysicsSet::Writeback).in_set(PhysicsSet::Writeback),
                 ),
             );
+
+            // Warn user if the timestep mode isn't in Fixed
+            if self.schedule.as_dyn_eq().dyn_eq(FixedUpdate.as_dyn_eq()) {
+                let config = app.world.resource::<RapierConfiguration>();
+                match config.timestep_mode {
+                    TimestepMode::Fixed { .. } => {}
+                    mode => {
+                        warn!("TimestepMode is set to `{:?}`, it is recommended to use `TimestepMode::Fixed` if you have the physics in `FixedUpdate`", mode);
+                    }
+                }
+            }
         }
     }
 }