parry3d/mass_properties/
mass_properties_ball.rs

1use crate::mass_properties::MassProperties;
2#[cfg(feature = "dim3")]
3use crate::math::Vector;
4use crate::math::{Point, PrincipalAngularInertia, Real};
5use na::RealField;
6
7impl MassProperties {
8    pub(crate) fn ball_volume_unit_angular_inertia(
9        radius: Real,
10    ) -> (Real, PrincipalAngularInertia<Real>) {
11        #[cfg(feature = "dim2")]
12        {
13            let volume = Real::pi() * radius * radius;
14            let i = radius * radius / 2.0;
15            (volume, i)
16        }
17        #[cfg(feature = "dim3")]
18        {
19            let volume = Real::pi() * radius * radius * radius * 4.0 / 3.0;
20            let i = radius * radius * 2.0 / 5.0;
21
22            (volume, Vector::repeat(i))
23        }
24    }
25
26    /// Computes the mass properties of a ball.
27    pub fn from_ball(density: Real, radius: Real) -> Self {
28        let (vol, unit_i) = Self::ball_volume_unit_angular_inertia(radius);
29        let mass = vol * density;
30        Self::new(Point::origin(), mass, unit_i * mass)
31    }
32}