73 lines
2.5 KiB
Rust
73 lines
2.5 KiB
Rust
use crate::dynamics::MassProperties;
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#[cfg(feature = "dim3")]
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use crate::geometry::Capsule;
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use crate::math::{Point, PrincipalAngularInertia, Rotation, Vector};
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impl MassProperties {
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fn cylinder_y_volume_unit_inertia(
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half_height: f32,
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radius: f32,
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) -> (f32, PrincipalAngularInertia<f32>) {
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#[cfg(feature = "dim2")]
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{
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Self::cuboid_volume_unit_inertia(Vector::new(radius, half_height))
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}
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#[cfg(feature = "dim3")]
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{
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let volume = half_height * radius * radius * std::f32::consts::PI * 2.0;
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let sq_radius = radius * radius;
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let sq_height = half_height * half_height * 4.0;
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let off_principal = (sq_radius * 3.0 + sq_height) / 12.0;
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let inertia = Vector::new(off_principal, sq_radius / 2.0, off_principal);
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(volume, inertia)
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}
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}
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pub(crate) fn from_capsule(density: f32, a: Point<f32>, b: Point<f32>, radius: f32) -> Self {
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let half_height = (b - a).norm() / 2.0;
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let (cyl_vol, cyl_unit_i) = Self::cylinder_y_volume_unit_inertia(half_height, radius);
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let (ball_vol, ball_unit_i) = Self::ball_volume_unit_angular_inertia(radius);
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let cap_vol = cyl_vol + ball_vol;
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let cap_mass = cap_vol * density;
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let mut cap_unit_i = cyl_unit_i + ball_unit_i;
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let local_com = na::center(&a, &b);
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#[cfg(feature = "dim2")]
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{
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let h = half_height * 2.0;
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let extra = h * h * 0.5 + h * radius * 3.0 / 8.0;
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cap_unit_i += extra;
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Self::new(local_com, cap_mass, cap_unit_i * cap_mass)
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}
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#[cfg(feature = "dim3")]
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{
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let h = half_height * 2.0;
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let extra = h * h * 0.5 + h * radius * 3.0 / 8.0;
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cap_unit_i.x += extra;
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cap_unit_i.z += extra;
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let local_frame = Capsule::new(a, b, radius).rotation_wrt_y();
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Self::with_principal_inertia_frame(
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local_com,
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cap_mass,
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cap_unit_i * cap_mass,
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local_frame,
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)
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}
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}
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#[cfg(feature = "dim3")]
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pub(crate) fn from_cylinder(density: f32, half_height: f32, radius: f32) -> Self {
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let (cyl_vol, cyl_unit_i) = Self::cylinder_y_volume_unit_inertia(half_height, radius);
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Self::with_principal_inertia_frame(
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Point::origin(),
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cyl_vol * density,
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cyl_unit_i * density,
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Rotation::identity(),
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)
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}
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}
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