from_angle_axis

kyosu::from_angle_axis = eve::functor<from_angle_axis_t>

inlineconstexpr

Callable object computing an an unitary quaternion from an angle value and a 3 dimensional axis vector.

Header file

#include kyosu/module/quaternion.hpp>`

Callable Signatures

namespace kyosu
{
  auto from_angle_axis(auto angle, auto axis) const noexcept;
  auto from_angle_axis[assume_unitary](auto angle, auto axis) const noexcept;
}

Parameters

• angle: rotation angle in radian
• axis: rotation axis given by an std::span of dimension 3.

Return value

1. the quaternion value representing the rotation. (if the axis is null the axis is normalized as (1, 0, 0)).
2. with assume_unitary the axis is NOT normalized before use, but the result is undefined if it is not the case.

Example

#include <kyosu/kyosu.hpp>
#include <eve/wide.hpp>
#include <array>
#include <iostream>
 
int main()
{
  using kyosu::from_angle_axis;
  using kyosu::complex_t;
  using kyosu::quaternion_t;
 
 
  auto theta = eve::pio_3(eve::as<double>());
  std::array<double, 3> ax{1., 2., 3.};
 
  std::cout << " <- theta = " << theta << std::endl;
  std::cout << " <- axis  = (" << ax[0] << ", " <<  ax[1] << ", " <<  ax[2] << ")" << std::endl;
  auto q = kyosu::from_angle_axis(theta,  std::span(ax));
  std::cout << " -> " << kyosu::from_angle_axis(theta, std::span(ax)) << "\n";
  auto [aa, axx] = kyosu::to_angle_axis(q);
  std::cout << " ->theta = " << aa << std::endl;
  std::cout << " -> axis  = (" << axx[0] << ", " <<  axx[1] << ", " <<  axx[2] << ")" << std::endl;
 
  std::array<double, 3> azz{0., 0., 0.};
  std::cout << kyosu::from_angle_axis(theta,  std::span(azz)) << std::endl;
  return 0;
}