path: root/src/utils.rs

//! Miscellaneous utilities.

use na::{Matrix3, Point2, Point3, Scalar, SimdRealField, Vector2, Vector3};
use num::Zero;
use simba::simd::SimdValue;
use std::ops::IndexMut;

use parry::utils::SdpMatrix3;
use {
    crate::math::{Real, SimdReal},
    na::SimdPartialOrd,
    num::One,
};

pub(crate) fn inv(val: Real) -> Real {
    if val == 0.0 {
        0.0
    } else {
        1.0 / val
    }
}

/// Trait to copy the sign of each component of one scalar/vector/matrix to another.
pub trait WSign<Rhs>: Sized {
    // See SIMD implementations of copy_sign there: https://stackoverflow.com/a/57872652
    /// Copy the sign of each component of `self` to the corresponding component of `to`.
    fn copy_sign_to(self, to: Rhs) -> Rhs;
}

impl WSign<Real> for Real {
    fn copy_sign_to(self, to: Self) -> Self {
        const MINUS_ZERO: Real = -0.0;
        let signbit = MINUS_ZERO.to_bits();
        Real::from_bits((signbit & self.to_bits()) | ((!signbit) & to.to_bits()))
    }
}

impl<N: Scalar + Copy + WSign<N>> WSign<Vector2<N>> for N {
    fn copy_sign_to(self, to: Vector2<N>) -> Vector2<N> {
        Vector2::new(self.copy_sign_to(to.x), self.copy_sign_to(to.y))
    }
}

impl<N: Scalar + Copy + WSign<N>> WSign<Vector3<N>> for N {
    fn copy_sign_to(self, to: Vector3<N>) -> Vector3<N> {
        Vector3::new(
            self.copy_sign_to(to.x),
            self.copy_sign_to(to.y),
            self.copy_sign_to(to.z),
        )
    }
}

impl<N: Scalar + Copy + WSign<N>> WSign<Vector2<N>> for Vector2<N> {
    fn copy_sign_to(self, to: Vector2<N>) -> Vector2<N> {
        Vector2::new(self.x.copy_sign_to(to.x), self.y.copy_sign_to(to.y))
    }
}

impl<N: Scalar + Copy + WSign<N>> WSign<Vector3<N>> for Vector3<N> {
    fn copy_sign_to(self, to: Vector3<N>) -> Vector3<N> {
        Vector3::new(
            self.x.copy_sign_to(to.x),
            self.y.copy_sign_to(to.y),
            self.z.copy_sign_to(to.z),
        )
    }
}

impl WSign<SimdReal> for SimdReal {
    fn copy_sign_to(self, to: SimdReal) -> SimdReal {
        to.simd_copysign(self)
    }
}

pub(crate) trait WComponent: Sized {
    type Element;

    fn min_component(self) -> Self::Element;
    fn max_component(self) -> Self::Element;
}

impl WComponent for Real {
    type Element = Real;

    fn min_component(self) -> Self::Element {
        self
    }
    fn max_component(self) -> Self::Element {
        self
    }
}

impl WComponent for SimdReal {
    type Element = Real;

    fn min_component(self) -> Self::Element {
        self.simd_horizontal_min()
    }
    fn max_component(self) -> Self::Element {
        self.simd_horizontal_max()
    }
}

/// Trait to compute the orthonormal basis of a vector.
pub trait WBasis: Sized {
    /// The type of the array of orthonormal vectors.
    type Basis;
    /// Computes the vectors which, when combined with `self`, form an orthonormal basis.
    fn orthonormal_basis(self) -> Self::Basis;
    /// Computes a vector orthogonal to `self` with a unit length (if `self` has a unit length).
    fn orthonormal_vector(self) -> Self;
}

impl<N: SimdRealField> WBasis for Vector2<N> {
    type Basis = [Vector2<N>; 1];
    fn orthonormal_basis(self) -> [Vector2<N>; 1] {
        [Vector2::new(-self.y, self.x)]
    }
    fn orthonormal_vector(self) -> Vector2<N> {
        Vector2::new(-self.y, self.x)
    }
}

impl<N: SimdRealField + WSign<N>> WBasis for Vector3<N> {
    type Basis = [Vector3<N>; 2];
    // Robust and branchless implementation from Pixar:
    // https://graphics.pixar.com/library/OrthonormalB/paper.pdf
    fn orthonormal_basis(self) -> [Vector3<N>; 2] {
        let sign = self.z.copy_sign_to(N::one());
        let a = -N::one() / (sign + self.z);
        let b = self.x * self.y * a;

        [
            Vector3::new(
                N::one() + sign * self.x * self.x * a,
                sign * b,
                -sign * self.x,
            ),
            Vector3::new(b, sign + self.y * self.y *