1 files changed, 30 insertions, 0 deletions
diff --git a/src/dynamics/mass_properties_ball.rs b/src/dynamics/mass_properties_ball.rs
new file mode 100644
index 0000000..ac5790a
--- /dev/null
+++ b/src/dynamics/mass_properties_ball.rs
@@ -0,0 +1,30 @@
+use crate::dynamics::MassProperties;
+#[cfg(feature = "dim3")]
+use crate::math::Vector;
+use crate::math::{Point, PrincipalAngularInertia};
+
+impl MassProperties {
+    pub(crate) fn ball_volume_unit_angular_inertia(
+        radius: f32,
+    ) -> (f32, PrincipalAngularInertia<f32>) {
+        #[cfg(feature = "dim2")]
+        {
+            let volume = std::f32::consts::PI * radius * radius;
+            let i = radius * radius / 2.0;
+            (volume, i)
+        }
+        #[cfg(feature = "dim3")]
+        {
+            let volume = std::f32::consts::PI * radius * radius * radius * 4.0 / 3.0;
+            let i = radius * radius * 2.0 / 5.0;
+
+            (volume, Vector::repeat(i))
+        }
+    }
+
+    pub(crate) fn from_ball(density: f32, radius: f32) -> Self {
+        let (vol, unit_i) = Self::ball_volume_unit_angular_inertia(radius);
+        let mass = vol * density;
+        Self::new(Point::origin(), mass, unit_i * mass)
+    }
+}