feat: change the character controller’s solve_character_collision_impulses to take multiple CharacterCollision (#646)

* character controller: solve multiple collisions

* add solve multiple collisions to changelog

* chore: apply review comments

---------

Co-authored-by: Sébastien Crozet <sebcrozet@dimforge.com>

3 files changed, 43 insertions, 15 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dcd0ae9..429fb82 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,6 +51,8 @@ This release introduces two new crates:
 - Rename `JointAxesMask::X/Y/Z` to `::LIN_X/LIN_Y/LIN_Z` to avoid confusing it with `::ANG_X/ANG_Y/ANG_Z`.
 - The function `RigidBody::add_collider` is now private. It was only public because it was needed for some internal
   `bevy_rapier` plumbings, but it is no longer useful. Adding a collider must always go througthe `ColliderSet`.
+- `CharacterController::solve_character_collision_impulses` now takes multiple `CharacterCollision` as parameter:
+  this change will allow further internal optimizations.
 
 ## v0.19.0 (05 May 2024)
 
diff --git a/src/control/character_controller.rs b/src/control/character_controller.rs
index 87b5c16..dc7381f 100644
--- a/src/control/character_controller.rs
+++ b/src/control/character_controller.rs
@@ -782,8 +782,8 @@ impl KinematicCharacterController {
         true
     }
 
-    /// For a given collision between a character and its environment, this method will apply
-    /// impulses to the rigid-bodies surrounding the character shape at the time of the collision.
+    /// For the given collisions between a character and its environment, this method will apply
+    /// impulses to the rigid-bodies surrounding the character shape at the time of the collisions.
     /// Note that the impulse calculation is only approximate as it is not based on a global
     /// constraints resolution scheme.
     pub fn solve_character_collision_impulses(
@@ -794,6 +794,35 @@ impl KinematicCharacterController {
         queries: &QueryPipeline,
         character_shape: &dyn Shape,
         character_mass: Real,
+        collisions: impl IntoIterator<Item = CharacterCollision>,
+        filter: QueryFilter,
+    ) {
+        for collision in collisions {
+            self.solve_single_character_collision_impulse(
+                dt,
+                bodies,
+                colliders,
+                queries,
+                character_shape,
+                character_mass,
+                &collision,
+                filter,
+            );
+        }
+    }
+
+    /// For the given collision between a character and its environment, this method will apply
+    /// impulses to the rigid-bodies surrounding the character shape at the time of the collision.
+    /// Note that the impulse calculation is only approximate as it is not based on a global
+    /// constraints resolution scheme.
+    fn solve_single_character_collision_impulse(
+        &self,
+        dt: Real,
+        bodies: &mut RigidBodySet,
+        colliders: &ColliderSet,
+        queries: &QueryPipeline,
+        character_shape: &dyn Shape,
+        character_mass: Real,
         collision: &CharacterCollision,
         filter: QueryFilter,
     ) {
diff --git a/src_testbed/testbed.rs b/src_testbed/testbed.rs
index 1defef6..dc747ed 100644
--- a/src_testbed/testbed.rs
+++ b/src_testbed/testbed.rs
@@ -811,19 +811,16 @@ impl<'a, 'b, 'c, 'd, 'e, 'f> Testbed<'a, 'b, 'c, 'd, 'e, 'f> {
                 QueryFilter::new().exclude_rigid_body(character_handle),
                 |c| collisions.push(c),
             );
-
-            for collision in &collisions {
-                controller.solve_character_collision_impulses(
-                    phx.integration_parameters.dt,
-                    &mut phx.bodies,
-                    &phx.colliders,
-                    &phx.query_pipeline,
-                    character_collider.shape(),
-                    character_mass,
-                    collision,
-                    QueryFilter::new().exclude_rigid_body(character_handle),
-                )
-            }
+            controller.solve_character_collision_impulses(
+                phx.integration_parameters.dt,
+                &mut phx.bodies,
+                &phx.colliders,
+                &phx.query_pipeline,
+                character_collider.shape(),
+                character_mass,
+                collisions,
+                QueryFilter::new().exclude_rigid_body(character_handle),
+            );
 
             let character_body = &mut phx.bodies[character_handle];
             let pos = character_body.position();