Ignition Math

API Reference

6.9.3~pre2
Rotation example

This example explains how to use quaternions and euler angles, and how to convert between them.

Compiling and running the code

Go to ign-math/examples and use cmake to compile the code:

git clone https://github.com/ignitionrobotics/ign-math/ -b ign-math6
cd ign-math/examples
mkdir build
cd build
cmake ..
make

When the code is compiled, you can run two different examples, one which converts from quaternion to euler angles:

Usage:
./quaternion_to_euler <float_w> <float_x> <float_y> <float_z>
Example
./quaternion_to_euler 0.5 0.5 0.5 0.5

And the other which converts from euler to quaternion:

quaternion_from_euler <float_roll> <float_pitch> <float_yaw>
Example
quaternion_from_euler 0 0 1.57

The ouput of each program, respectively:

./quaternion_to_euler 0.5 0.5 0.5 0.5
Normalizing Quaternion components:
W 0.5
X 0.5
Y 0.5
Z 0.5
to
W 0.5
X 0.5
Y 0.5
Z 0.5
Converting to Euler angles
roll 90.000000 degrees
pitch -0.000000 degrees
yaw 90.000000 degrees
to Rotation matrix
0.000000 0.000000 1.000000
1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
./quaternion_from_euler 0 0 1.57
Converting Euler angles:
roll 0.000000 degrees
pitch 0.000000 degrees
yaw 89.954374 degrees
to Quaternion
W 0.707388
X 0.000000
Y 0.000000
Z 0.706825
to Rotation matrix
0.000796 -1.000000 0.000000
1.000000 0.000796 0.000000
0.000000 0.000000 1.000000

Code

You can create some objects to express rotations:

ignition::math::Quaterniond q(roll, pitch, yaw);
ignition::math::Vector3d euler(q.Euler());

To access the quaterions attributes:

printf(" W % .6f\n X % .6f\n Y % .6f\n Z % .6f\n",
q.W(), q.X(), q.Y(), q.Z());

Or to acccess the rotation matrix elements:

std::cout << "\nto Rotation matrix\n";
printf(" % .6f % .6f % .6f\n"
" % .6f % .6f % .6f\n"
" % .6f % .6f % .6f\n",
m(0, 0), m(0, 1), m(0, 2),
m(1, 0), m(1, 1), m(1, 2),
m(2, 0), m(2, 1), m(2, 2));