Fix mass-properties update after collider change

src/pipeline/collision_pipeline.rs

@@ -3,12 +3,12 @@
 use crate::data::{ComponentSet, ComponentSetMut, ComponentSetOption};
 use crate::dynamics::{
     RigidBodyActivation, RigidBodyChanges, RigidBodyColliders, RigidBodyDominance, RigidBodyHandle,
-    RigidBodyIds, RigidBodyPosition, RigidBodyType, RigidBodyVelocity,
+    RigidBodyIds, RigidBodyMassProps, RigidBodyPosition, RigidBodyType, RigidBodyVelocity,
 };
 use crate::geometry::{
     BroadPhase, BroadPhasePairEvent, ColliderBroadPhaseData, ColliderChanges, ColliderFlags,
-    ColliderHandle, ColliderMaterial, ColliderPair, ColliderParent, ColliderPosition,
-    ColliderShape, ColliderType, NarrowPhase,
+    ColliderHandle, ColliderMassProps, ColliderMaterial, ColliderPair, ColliderParent,
+    ColliderPosition, ColliderShape, ColliderType, NarrowPhase,
 };
 use crate::math::Real;
 use crate::pipeline::{EventHandler, PhysicsHooks};
@@ -169,6 +169,7 @@ impl CollisionPipeline {
             + ComponentSetMut<RigidBodyIds>
             + ComponentSetMut<RigidBodyActivation>
             + ComponentSetMut<RigidBodyChanges>
+            + ComponentSetMut<RigidBodyMassProps>
             + ComponentSet<RigidBodyColliders>
             + ComponentSet<RigidBodyDominance>
             + ComponentSet<RigidBodyType>,
@@ -179,7 +180,8 @@ impl CollisionPipeline {
             + ComponentSetOption<ColliderParent>
             + ComponentSet<ColliderType>
             + ComponentSet<ColliderMaterial>
-            + ComponentSet<ColliderFlags>,
+            + ComponentSet<ColliderFlags>
+            + ComponentSet<ColliderMassProps>,
     {
         super::user_changes::handle_user_changes_to_colliders(
             bodies,

src/pipeline/physics_pipeline.rs

@@ -15,7 +15,7 @@ use crate::dynamics::{JointGraphEdge, ParallelIslandSolver as IslandSolver};
 use crate::geometry::{
     BroadPhase, BroadPhasePairEvent, ColliderBroadPhaseData, ColliderChanges, ColliderFlags,
     ColliderHandle, ColliderMaterial, ColliderPair, ColliderParent, ColliderPosition,
-    ColliderShape, ColliderType, ContactManifoldIndex, NarrowPhase,
+    ColliderShape, ColliderType, ContactManifoldIndex, NarrowPhase, ColliderMassProps
 };
 use crate::math::{Real, Vector};
 use crate::pipeline::{EventHandler, PhysicsHooks};
@@ -504,7 +504,8 @@ impl PhysicsPipeline {
             + ComponentSetOption<ColliderParent>
             + ComponentSet<ColliderType>
             + ComponentSet<ColliderMaterial>
-            + ComponentSet<ColliderFlags>,
+            + ComponentSet<ColliderFlags>
+            + ComponentSet<ColliderMassProps>,
     {
         self.counters.reset();
         self.counters.step_started();

src/pipeline/user_changes.rs

@@ -1,39 +1,75 @@
 use crate::data::{BundleSet, ComponentSet, ComponentSetMut, ComponentSetOption};
 use crate::dynamics::{
     IslandManager, RigidBodyActivation, RigidBodyChanges, RigidBodyColliders, RigidBodyHandle,
-    RigidBodyIds, RigidBodyPosition, RigidBodyType,
+    RigidBodyIds, RigidBodyMassProps, RigidBodyPosition, RigidBodyType,
 };
-use crate::geometry::{ColliderChanges, ColliderHandle, ColliderParent, ColliderPosition};
+use crate::geometry::{
+    ColliderChanges, ColliderHandle, ColliderMassProps, ColliderParent, ColliderPosition,
+    ColliderShape,
+};
+use parry::utils::hashmap::HashMap;
 
-pub(crate) fn handle_user_changes_to_colliders<Colliders>(
-    bodies: &mut impl ComponentSet<RigidBodyPosition>,
+pub(crate) fn handle_user_changes_to_colliders<Bodies, Colliders>(
+    bodies: &mut Bodies,
     colliders: &mut Colliders,
     modified_colliders: &[ColliderHandle],
 ) where
+    Bodies: ComponentSet<RigidBodyPosition>
+        + ComponentSet<RigidBodyColliders>
+        + ComponentSetMut<RigidBodyMassProps>,
     Colliders: ComponentSetMut<ColliderChanges>
         + ComponentSetMut<ColliderPosition>
-        + ComponentSetOption<ColliderParent>,
+        + ComponentSetOption<ColliderParent>
+        + ComponentSet<ColliderShape>
+        + ComponentSet<ColliderMassProps>,
 {
+    // TODO: avoid this hashmap? We could perhaps add a new flag to RigidBodyChanges to
+    //       indicated that the mass properties need to be recomputed?
+    let mut mprops_to_update = HashMap::default();
+
     for handle in modified_colliders {
         // NOTE: we use `get` because the collider may no longer
         //       exist if it has been removed.
-        let co_changes: Option<&ColliderChanges> = colliders.get(handle.0);
+        let co_changes: Option<ColliderChanges> = colliders.get(handle.0).copied();
 
         if let Some(co_changes) = co_changes {
             if co_changes.contains(ColliderChanges::PARENT) {
                 let co_parent: Option<&ColliderParent> = colliders.get(handle.0);
 
                 if let Some(co_parent) = co_parent {
-                    let parent_pos = bodies.index(co_parent.handle.0);
+                    let parent_pos: &RigidBodyPosition = bodies.index(co_parent.handle.0);
 
                     let new_pos = parent_pos.position * co_parent.pos_wrt_parent;
-                    let new_changes = *co_changes | ColliderChanges::POSITION;
+                    let new_changes = co_changes | ColliderChanges::POSITION;
                     colliders.set_internal(handle.0, ColliderPosition(new_pos));
                     colliders.set_internal(handle.0, new_changes);
                 }
             }
+
+            if co_changes.contains(ColliderChanges::SHAPE) {
+                let co_parent: Option<&ColliderParent> = colliders.get(handle.0);
+                if let Some(co_parent) = co_parent {
+                    mprops_to_update.insert(co_parent.handle, ());
+                }
+            }
         }
     }
+
+    for (to_update, _) in mprops_to_update {
+        let (rb_pos, rb_colliders): (&RigidBodyPosition, &RigidBodyColliders) =
+            bodies.index_bundle(to_update.0);
+        let position = rb_pos.position;
+        // FIXME: remove the clone once we remove the ComponentSets.
+        let attached_colliders = rb_colliders.clone();
+
+        bodies.map_mut_internal(to_update.0, |rb_mprops| {
+            rb_mprops.recompute_mass_properties_from_colliders(
+                colliders,
+                &attached_colliders,
+                &position,
+            )
+        });
+    }
 }
 
 pub(crate) fn handle_user_changes_to_rigid_bodies<Bodies, Colliders>(