Fix cylinder inertia tensor computation.

src/dynamics/mass_properties_capsule.rs

@@ -4,27 +4,6 @@ use crate::geometry::Capsule;
 use crate::math::{Point, PrincipalAngularInertia, Rotation, Vector};
 
 impl MassProperties {
-    fn cylinder_y_volume_unit_inertia(
-        half_height: f32,
-        radius: f32,
-    ) -> (f32, PrincipalAngularInertia<f32>) {
-        #[cfg(feature = "dim2")]
-        {
-            Self::cuboid_volume_unit_inertia(Vector::new(radius, half_height))
-        }
-
-        #[cfg(feature = "dim3")]
-        {
-            let volume = half_height * radius * radius * std::f32::consts::PI * 2.0;
-            let sq_radius = radius * radius;
-            let sq_height = half_height * half_height * 4.0;
-            let off_principal = (sq_radius * 3.0 + sq_height) / 12.0;
-
-            let inertia = Vector::new(off_principal, sq_radius / 2.0, off_principal);
-            (volume, inertia)
-        }
-    }
-
     pub(crate) fn from_capsule(density: f32, a: Point<f32>, b: Point<f32>, radius: f32) -> Self {
         let half_height = (b - a).norm() / 2.0;
         let (cyl_vol, cyl_unit_i) = Self::cylinder_y_volume_unit_inertia(half_height, radius);
@@ -57,16 +36,4 @@ impl MassProperties {
             )
         }
     }
-
-    #[cfg(feature = "dim3")]
-    pub(crate) fn from_cylinder(density: f32, half_height: f32, radius: f32) -> Self {
-        let (cyl_vol, cyl_unit_i) = Self::cylinder_y_volume_unit_inertia(half_height, radius);
-
-        Self::with_principal_inertia_frame(
-            Point::origin(),
-            cyl_vol * density,
-            cyl_unit_i * density,
-            Rotation::identity(),
-        )
-    }
 }

src/dynamics/mass_properties_cylinder.rs

@@ -0,0 +1,40 @@
+use crate::dynamics::MassProperties;
+#[cfg(feature = "dim3")]
+use crate::geometry::Capsule;
+use crate::math::{Point, PrincipalAngularInertia, Rotation, Vector};
+
+impl MassProperties {
+    pub(crate) fn cylinder_y_volume_unit_inertia(
+        half_height: f32,
+        radius: f32,
+    ) -> (f32, PrincipalAngularInertia<f32>) {
+        #[cfg(feature = "dim2")]
+        {
+            Self::cuboid_volume_unit_inertia(Vector::new(radius, half_height))
+        }
+
+        #[cfg(feature = "dim3")]
+        {
+            let volume = half_height * radius * radius * std::f32::consts::PI * 2.0;
+            let sq_radius = radius * radius;
+            let sq_height = half_height * half_height * 4.0;
+            let off_principal = (sq_radius * 3.0 + sq_height) / 12.0;
+
+            let inertia = Vector::new(off_principal, sq_radius / 2.0, off_principal);
+            (volume, inertia)
+        }
+    }
+
+    #[cfg(feature = "dim3")]
+    pub(crate) fn from_cylinder(density: f32, half_height: f32, radius: f32) -> Self {
+        let (cyl_vol, cyl_unit_i) = Self::cylinder_y_volume_unit_inertia(half_height, radius);
+        let cyl_mass = cyl_vol * density;
+
+        Self::with_principal_inertia_frame(
+            Point::origin(),
+            cyl_mass,
+            cyl_unit_i * cyl_mass,
+            Rotation::identity(),
+        )
+    }
+}

src/dynamics/mod.rs

@@ -23,6 +23,7 @@ mod mass_properties;
 mod mass_properties_ball;
 mod mass_properties_capsule;
 mod mass_properties_cuboid;
+mod mass_properties_cylinder;
 #[cfg(feature = "dim2")]
 mod mass_properties_polygon;
 mod rigid_body;