Impl Default for a few structs

src/dynamics/ccd/ccd_solver.rs

@@ -29,6 +29,12 @@ pub struct CCDSolver {
     query_pipeline: QueryPipeline,
 }
 
+impl Default for CCDSolver {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl CCDSolver {
     /// Initializes a new CCD solver
     pub fn new() -> Self {

src/dynamics/island_manager.rs

@@ -9,7 +9,7 @@ use crate::math::Real;
 /// Structure responsible for maintaining the set of active rigid-bodies, and
 /// putting non-moving rigid-bodies to sleep to save computation times.
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct IslandManager {
     pub(crate) active_dynamic_set: Vec<RigidBodyHandle>,
     pub(crate) active_kinematic_set: Vec<RigidBodyHandle>,

src/dynamics/joint/joint_set.rs

@@ -37,7 +37,7 @@ pub(crate) type JointIndex = usize;
 pub(crate) type JointGraphEdge = crate::data::graph::Edge<Joint>;
 
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-#[derive(Clone)]
+#[derive(Clone, Default)]
 /// A set of joints that can be handled by a physics `World`.
 pub struct JointSet {
     rb_graph_ids: Coarena<RigidBodyGraphIndex>,

src/dynamics/rigid_body.rs

@@ -36,6 +36,12 @@ pub struct RigidBody {
     pub user_data: u128,
 }
 
+impl Default for RigidBody {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl RigidBody {
     fn new() -> Self {
         Self {

src/dynamics/rigid_body_set.rs

@@ -28,7 +28,7 @@ impl BodyPair {
 }
 
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
-#[derive(Clone)]
+#[derive(Clone, Default)]
 /// A set of rigid bodies that can be handled by a physics pipeline.
 pub struct RigidBodySet {
     // NOTE: the pub(crate) are needed by the broad phase

src/dynamics/solver/island_solver.rs

@@ -19,6 +19,12 @@ pub struct IslandSolver {
     position_solver: PositionSolver,
 }
 
+impl Default for IslandSolver {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl IslandSolver {
     pub fn new() -> Self {
         Self {

src/dynamics/solver/parallel_island_solver.rs

@@ -133,6 +133,12 @@ pub struct ParallelIslandSolver {
     thread: ThreadContext,
 }
 
+impl Default for ParallelIslandSolver {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl ParallelIslandSolver {
     pub fn new() -> Self {
         Self {