feat: add a BroadPhaseTrait for allowing custom broad-phases

1 files changed, 47 insertions, 0 deletions

diff --git a/src/geometry/broad_phase.rs b/src/geometry/broad_phase.rs
new file mode 100644
index 0000000..e51c351
--- /dev/null
+++ b/src/geometry/broad_phase.rs
@@ -0,0 +1,47 @@
+use crate::geometry::{BroadPhasePairEvent, ColliderHandle, ColliderSet};
+use parry::math::Real;
+
+/// An internal index stored in colliders by some broad-phase algorithms.
+pub type BroadPhaseProxyIndex = u32;
+
+/// Trait implemented by broad-phase algorithms supported by Rapier.
+///
+/// The task of a broad-phase algorithm is to detect potential collision pairs, usually based on
+/// bounding volumes. The pairs must be concervative: it is OK to create a collision pair if
+/// two objects don’t actually touch, but it is incorrect to remove a pair between two objects
+/// that are still touching. In other words, it can have false-positive (though these induce
+/// some computational overhead on the narrow-phase), but cannot have false-negative.
+pub trait BroadPhase {
+    /// Updates the broad-phase.
+    ///
+    /// The results must be output through the `events` struct. The broad-phase algorithm is only
+    /// required to generate new events (i.e. no need to re-send an `AddPair` event if it was already
+    /// sent previously and no `RemovePair` happened since then). Sending redundant events is allowed
+    /// but can result in a slight computational overhead.
+    ///
+    /// The `colliders` set is mutable only to provide access to
+    /// [`collider.set_internal_broad_phase_proxy_index`]. Other properties of the collider should
+    /// **not** be modified during the broad-phase update.
+    ///
+    /// # Parameters
+    /// - `prediction_distance`: colliders that are not exactly touching, but closer to this
+    ///   distance must form a collision pair.
+    /// - `colliders`: the set of colliders. Change detection with `collider.needs_broad_phase_update()`
+    ///   can be relied on at this stage.
+    /// - `modified_colliders`: colliders that are know to be modified since the last update.
+    /// - `removed_colliders`: colliders that got removed since the last update. Any associated data
+    ///   in the broad-phase should be removed by this call to `update`.
+    /// - `events`: the broad-phase’s output. They indicate what collision pairs need to be created
+    ///   and what pairs need to be removed. It is OK to create pairs for colliders that don’t
+    ///   actually collide (though this can increase computational overhead in the narrow-phase)
+    ///   but it is important not to indicate removal of a collision pair if the underlying colliders
+    ///   are still touching or closer than `prediction_distance`.
+    fn update(
+        &mut self,
+        prediction_distance: Real,
+        colliders: &mut ColliderSet,
+        modified_colliders: &[ColliderHandle],
+        removed_colliders: &[ColliderHandle],
+        events: &mut Vec<BroadPhasePairEvent>,
+    );
+}