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use na::{self, RealField};
use na::{Isometry2, Isometry3, Matrix1, Matrix3, Point2, Point3, Vector1, Vector3};
use crate::math::{AngularInertia, Inertia, Point};
pub trait InertiaTensor<N, P, AV, M> {
fn apply(&self, a: &AV) -> AV;
fn to_world_space(&self, _: &M) -> Self;
fn to_relative_wrt_point(&self, _: N, _: &P) -> Self;
}
pub trait Volumetric<N: RealField> {
fn area(&self) -> N;
fn volume(&self) -> N;
fn center_of_mass(&self) -> Point<N>;
fn unit_angular_inertia(&self) -> AngularInertia<N>;
fn mass(&self, density: N) -> N {
self.volume() * density
}
fn angular_inertia(&self, mass: N) -> AngularInertia<N> {
self.unit_angular_inertia() * mass
}
fn mass_properties(&self, density: N) -> (N, Point<N>, AngularInertia<N>) {
let mass = self.mass(density);
let com = self.center_of_mass();
let ai = self.angular_inertia(mass);
(mass, com, ai)
}
fn inertia(&self, density: N) -> Inertia<N> {
let (mass, _, ai) = self.mass_properties(density);
Inertia::new_with_angular_matrix(mass, ai)
}
}
impl<N: RealField> InertiaTensor<N, Point2<N>, Vector1<N>, Isometry2<N>> for Matrix1<N> {
#[inline]
fn apply(&self, av: &Vector1<N>) -> Vector1<N> {
*self * *av
}
#[inline]
fn to_world_space(&self, _: &Isometry2<N>) -> Matrix1<N> {
*self
}
#[inline]
fn to_relative_wrt_point(&self, mass: N, pt: &Point2<N>) -> Matrix1<N> {
*self + Matrix1::new(mass * pt.coords.norm_squared())
}
}
impl<N: RealField> InertiaTensor<N, Point3<N>, Vector3<N>, Isometry3<N>> for Matrix3<N> {
#[inline]
fn apply(&self, av: &Vector3<N>) -> Vector3<N> {
*self * *av
}
#[inline]
fn to_world_space(&self, t: &Isometry3<N>) -> Matrix3<N> {
let rot = t.rotation.to_rotation_matrix();
let irot = rot.inverse();
rot * *self * irot
}
#[inline]
fn to_relative_wrt_point(&self, mass: N, pt: &Point3<N>) -> Matrix3<N> {
let diag = pt.coords.norm_squared();
let diagm = Matrix3::new(
diag,
na::zero(),
na::zero(),
na::zero(),
diag,
na::zero(),
na::zero(),
na::zero(),
diag,
);
*self + (diagm - pt.coords * pt.coords.transpose()) * mass
}
}