align

kyosu::align = eve::functor<align_t>

inlineconstexpr

Callable object computing an unitary quaternion value representing a rotation that align v0 to v1.

Return value An unitary quaternion value representing a rotation that align v0 to v1. If v0 or v01 is a nullvector the result is one as a quaternion.

Note

by default v0 and v1 are not assumed unitary (vectors of norm 1). If it is the case the decorator assume_unitary can be used.

Example

#include <kyosu/kyosu.hpp>
#include <eve/wide.hpp>
#include <iostream>
 
int main()
{
  using kyosu::align;
  auto norm = [](auto &v){
    auto n = eve::hypot(v[0], v[1], v[2]);
    for(int i=0; i <= 2; ++i) v[i]/= n;
  };
 
  std::array<double, 3> v0{-1.0, 5.0, 4.0};
  std::array<double, 3> v1{ 1.5, 2.0, -3.0};
  norm(v0);
  norm(v1);
  auto q = kyosu::align(std::span(v0), std::span(v1));
  std::cout << " v0                " << v0[0] << ", " << v0[1] << ",  " <<  v0[2] << "\n";
  std::cout << " v1                " << v1[0] << ", " << v1[1] << ",  " <<  v1[2] << "\n";
  std::cout << " q                 " << q << std::endl;
  auto rv = kyosu::rotate_vec(q, std::span(v0));
  std::cout << " rotate_vec(q, v0) " << rv[0] << ", " << rv[1] << ",  " << rv[2] << "\n";
 
  return 0;
}

Header file

#include kyosu/module/quaternion.hpp>`

Callable Signatures

namespace kyosu
{
  auto align(auto v1, auto v2)                 const noexcept;
  auto align[assume_unitary](auto v1, auto v2) const noexcept;
}

Parameters

• v0: span of 3 elements
• v1: span of 3 elements