https://github.com/pdebuyl/fortran_quaternion

Basic quaternion operations
https://github.com/pdebuyl/fortran_quaternion

fortran

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Basic quaternion operations

• Host: GitHub
• URL: https://github.com/pdebuyl/fortran_quaternion
• Owner: pdebuyl
• License: bsd-3-clause
• Created: 2017-02-05T21:54:44.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-03-02T14:44:00.000Z (over 7 years ago)
• Last Synced: 2024-01-29T08:46:52.223Z (9 months ago)
• Topics: fortran
• Language: Fortran
• Size: 13.7 KB
• Stars: 11
• Watchers: 3
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# fortran_quaternion

**Author:** Pierre de Buyl  

**License:** 3-clause BSD

[![Build Status](https://travis-ci.org/pdebuyl/fortran_quaternion.svg?branch=master)](https://travis-ci.org/pdebuyl/fortran_quaternion)

`fortran_quaternion` is a Fortran module that provides some basic quaternion functions.

`fortran_quaternion` does not define any derived type, instead quaternions are provided as

4-element vectors storing the vector part first and the scalar part last.

- `qnew`: return a quaternion from the scalar and vector input.

- `qvector`: return the vector part of a quaternion.

- `qscalar`: return the scalar part of a quaternion.

- `qnorm`: return the norm.

- `qnormalize`: return the normalized quaternion.

- `qconj`: return the conjugate.

- `qinv`: return the inverse.

- `qmul`: return the product of two quaternions.

## Example programs

### Multiplication of two quaternions

~~~.f90

program quaternion_usage

  use quaternion

  implicit none

  double precision :: q1(4), q2(4)

  q1 = qnew(v=[1.d0, 2.d0, 3.d0], s=4.d0)

  q2 = qnew(v=[6.d0, 7.d0, 8.d0], s=5.d0)

  write(*,'(4f5.2,a,4f5.2)') q1, ' x ', q2

  write(*,'(a,4f7.2)') '= ', qmul(q1, q2)

end program quaternion_usage

~~~

### Rotation of a 3d vector about a given axis

~~~.f90

program quaternion_rotation

  use quaternion

  implicit none

  double precision :: q(4), v(3)

  double precision :: axis(3), theta

  axis = [ 1, 1, 0 ]

  theta = 2*atan(1.d0) ! pi/2

  q = qnew(s=cos(theta/2), v=sin(theta/2)*axis/norm2(axis))

  v = [0, 0, 1]

  write(*,'(a,3f7.2)') 'v = ', v

  ! Rotate qv by q

  v = qvector(qmul(q, qmul(qnew(v=v), qconj(q))))

  write(*,'(a,3f7.2)') 'rotated v = ', v

end program quaternion_rotation

~~~

## Installation

Copy the file `src/quaternion.f90` *or* use cmake (with the `add_subdirectory` command) to

add the library to your project.

## Tests

Tests are defined in `test/` and rely on

[fortran_tester](https://github.com/pdebuyl/fortran_tester), installed via git submodules:

    git submodule init

    git submodule update