Mass Property Rework

README.md

@@ -121,7 +121,7 @@ fn setup(
         Collider::cuboid(1.0, 1.0, 1.0),
         AngularVelocity(Vec3::new(2.5, 3.5, 1.5)),
         PbrBundle {
-            mesh: meshes.add(Cuboid::new(1.0, 1.0, 1.0)),
+            mesh: meshes.add(Cuboid::from_length(1.0)),
             material: materials.add(Color::srgb_u8(124, 144, 255)),
             transform: Transform::from_xyz(0.0, 4.0, 0.0),
             ..default()

crates/avian2d/Cargo.toml

@@ -33,6 +33,7 @@ enhanced-determinism = [
     "parry2d?/enhanced-determinism",
     "parry2d-f64?/enhanced-determinism",
     "bevy_math/libm",
+    "bevy_heavy/libm",
 ]
 
 default-collider = ["dep:nalgebra"]
@@ -61,6 +62,7 @@ bench = false
 avian_derive = { path = "../avian_derive", version = "0.1" }
 bevy = { version = "0.15", default-features = false }
 bevy_math = { version = "0.15" }
+bevy_heavy = { version = "0.1" }
 libm = { version = "0.2", optional = true }
 parry2d = { version = "0.17", optional = true }
 parry2d-f64 = { version = "0.17", optional = true }
@@ -76,6 +78,7 @@ bitflags = "2.5.0"
 examples_common_2d = { path = "../examples_common_2d" }
 benches_common_2d = { path = "../benches_common_2d" }
 bevy_math = { version = "0.15", features = ["approx"] }
+bevy_heavy = { version = "0.1", features = ["approx"] }
 glam = { version = "0.29", features = ["bytemuck"] }
 approx = "0.5"
 bytemuck = "1.19"

crates/avian2d/examples/chain_2d.rs

@@ -49,7 +49,7 @@ fn setup(
         let current_particle = commands
             .spawn((
                 RigidBody::Dynamic,
-                MassPropertiesBundle::new_computed(&Collider::circle(particle_radius), 1.0),
+                MassPropertiesBundle::from_shape(&Circle::new(particle_radius as f32), 1.0),
                 Mesh2d(particle_mesh.clone()),
                 MeshMaterial2d(particle_material.clone()),
                 Transform::from_xyz(0.0, -i as f32 * (particle_radius as f32 * 2.0 + 1.0), 0.0),

crates/avian2d/examples/custom_collider.rs

@@ -1,5 +1,7 @@
 //! An example demonstrating how to make a custom collider and use it for collision detection.
 
+#![allow(clippy::unnecessary_cast)]
+
 use avian2d::{math::*, prelude::*};
 use bevy::prelude::*;
 use examples_common_2d::ExampleCommonPlugin;
@@ -55,21 +57,8 @@ impl AnyCollider for CircleCollider {
         ColliderAabb::new(position, Vector::splat(self.radius))
     }
 
-    fn mass_properties(&self, density: Scalar) -> ColliderMassProperties {
-        // In 2D, the Z length is assumed to be 1.0, so volume = area
-        let volume = PI * self.radius.powi(2);
-        let mass = density * volume;
-        let angular_inertia = mass * self.radius.powi(2) / 2.0;
-
-        ColliderMassProperties {
-            mass,
-            angular_inertia,
-            center_of_mass: default(),
-        }
-    }
-
     // This is the actual collision detection part.
-    // It compute all contacts between two colliders at the given positions.
+    // It computes all contacts between two colliders at the given positions.
     fn contact_manifolds(
         &self,
         other: &Self,
@@ -122,6 +111,25 @@ impl AnyCollider for CircleCollider {
     }
 }
 
+// Implement mass computation for the collider shape.
+// This is needed for physics to behave correctly.
+impl ComputeMassProperties2d for CircleCollider {
+    fn mass(&self, density: f32) -> f32 {
+        // In 2D, the Z length is assumed to be `1.0`, so volume == area.
+        let volume = std::f32::consts::PI * self.radius.powi(2) as f32;
+        density * volume
+    }
+
+    fn unit_angular_inertia(&self) -> f32 {
+        // Angular inertia for a circle, assuming a mass of `1.0`.
+        self.radius.powi(2) as f32 / 2.0
+    }
+
+    fn center_of_mass(&self) -> Vec2 {
+        Vec2::ZERO
+    }
+}
+
 // Note: This circle collider only supports uniform scaling.
 impl ScalableCollider for CircleCollider {
     fn scale(&self) -> Vector {

crates/avian2d/examples/distance_joint_2d.rs

@@ -34,7 +34,7 @@ fn setup(mut commands: Commands) {
             square_sprite,
             Transform::from_xyz(100.0, 0.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::rectangle(50.0, 50.0), 1.0),
+            MassPropertiesBundle::from_shape(&Rectangle::from_length(50.0), 1.0),
         ))
         .id();
 

crates/avian2d/examples/fixed_joint_2d.rs

@@ -38,7 +38,7 @@ fn setup(mut commands: Commands) {
             square_sprite,
             Transform::from_xyz(100.0, 0.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::rectangle(50.0, 50.0), 1.0),
+            MassPropertiesBundle::from_shape(&Rectangle::from_length(50.0), 1.0),
         ))
         .id();
 

crates/avian2d/examples/prismatic_joint_2d.rs

@@ -38,7 +38,7 @@ fn setup(mut commands: Commands) {
             square_sprite,
             Transform::from_xyz(100.0, 0.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::rectangle(50.0, 50.0), 1.0),
+            MassPropertiesBundle::from_shape(&Rectangle::from_length(50.0), 1.0),
         ))
         .id();
 

crates/avian2d/examples/revolute_joint_2d.rs

@@ -38,7 +38,7 @@ fn setup(mut commands: Commands) {
             square_sprite,
             Transform::from_xyz(0.0, -100.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::rectangle(50.0, 50.0), 1.0),
+            MassPropertiesBundle::from_shape(&Rectangle::from_length(50.0), 1.0),
         ))
         .id();
 

crates/avian3d/Cargo.toml

@@ -34,6 +34,7 @@ enhanced-determinism = [
     "parry3d?/enhanced-determinism",
     "parry3d-f64?/enhanced-determinism",
     "bevy_math/libm",
+    "bevy_heavy/libm",
 ]
 
 default-collider = ["dep:nalgebra"]
@@ -48,6 +49,7 @@ bevy_picking = ["bevy/bevy_picking"]
 serialize = [
     "dep:serde",
     "bevy/serialize",
+    "bevy_heavy/serialize",
     "parry3d?/serde-serialize",
     "parry3d-f64?/serde-serialize",
     "bitflags/serde",
@@ -63,6 +65,7 @@ bench = false
 avian_derive = { path = "../avian_derive", version = "0.1" }
 bevy = { version = "0.15", default-features = false }
 bevy_math = { version = "0.15" }
+bevy_heavy = { version = "0.1" }
 libm = { version = "0.2", optional = true }
 parry3d = { version = "0.17", optional = true }
 parry3d-f64 = { version = "0.17", optional = true }
@@ -75,13 +78,14 @@ itertools = "0.13"
 bitflags = "2.5.0"
 
 [dev-dependencies]
+examples_common_3d = { path = "../examples_common_3d" }
+benches_common_3d = { path = "../benches_common_3d" }
 bevy = { version = "0.15", default-features = false, features = [
     "bevy_gltf",
     "animation",
 ] }
-examples_common_3d = { path = "../examples_common_3d" }
-benches_common_3d = { path = "../benches_common_3d" }
 bevy_math = { version = "0.15", features = ["approx"] }
+bevy_heavy = { version = "0.1", features = ["approx"] }
 approx = "0.5"
 criterion = { version = "0.5", features = ["html_reports"] }
 bevy_mod_debugdump = { git = "https://github.com/jakobhellermann/bevy_mod_debugdump" }

crates/avian3d/examples/chain_3d.rs

@@ -56,7 +56,7 @@ fn setup(
         let current_particle = commands
             .spawn((
                 RigidBody::Dynamic,
-                MassPropertiesBundle::new_computed(&Collider::sphere(particle_radius), 1.0),
+                MassPropertiesBundle::from_shape(&Sphere::new(particle_radius as f32), 1.0),
                 Mesh3d(particle_mesh.clone()),
                 MeshMaterial3d(particle_material.clone()),
                 Transform::from_xyz(0.0, -i as f32 * particle_radius as f32 * 2.2, 0.0),

crates/avian3d/examples/custom_constraint.rs

@@ -119,7 +119,7 @@ fn setup(
             MeshMaterial3d(cube_material),
             Transform::from_xyz(3.0, 3.5, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::cuboid(1.0, 1.0, 1.0), 1.0),
+            MassPropertiesBundle::from_shape(&Cuboid::from_length(1.0), 1.0),
         ))
         .id();
 

crates/avian3d/examples/distance_joint_3d.rs

@@ -38,7 +38,6 @@ fn setup(
             Transform::from_xyz(-2.0, -0.5, 0.0),
             RigidBody::Dynamic,
             Collider::cuboid(1., 1., 1.),
-            MassPropertiesBundle::new_computed(&Collider::cuboid(1.0, 1.0, 1.0), 1.0),
         ))
         .id();
 

crates/avian3d/examples/fixed_joint_3d.rs

@@ -40,7 +40,7 @@ fn setup(
             MeshMaterial3d(cube_material),
             Transform::from_xyz(1.5, 0.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::cuboid(1.0, 1.0, 1.0), 1.0),
+            MassPropertiesBundle::from_shape(&Cuboid::from_length(1.0), 1.0),
         ))
         .id();
 

crates/avian3d/examples/prismatic_joint_3d.rs

@@ -40,7 +40,7 @@ fn setup(
             MeshMaterial3d(cube_material),
             Transform::from_xyz(1.5, 0.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::cuboid(1.0, 1.0, 1.0), 1.0),
+            MassPropertiesBundle::from_shape(&Cuboid::from_length(1.0), 1.0),
         ))
         .id();
 

crates/avian3d/examples/revolute_joint_3d.rs

@@ -40,7 +40,7 @@ fn setup(
             MeshMaterial3d(cube_material),
             Transform::from_xyz(0.0, -2.0, 0.0),
             RigidBody::Dynamic,
-            MassPropertiesBundle::new_computed(&Collider::cuboid(1.0, 1.0, 1.0), 1.0),
+            MassPropertiesBundle::from_shape(&Cuboid::from_length(1.0), 1.0),
         ))
         .id();