A simple HTML+JavaScript page to convert between different 3D rotation formats, quaternions, Rodrigues angles, Euler angles, etc.
Run http://www.andre-gaschler.com/rotationconverter/ directly to convert rotations online
Most of the conversion is calculated with the three.js library (which is also MIT-licensed).
Permissive MIT license, see file LICENSE
To generate the minified math part of three.js, call
python three.js-master/utils/build/build.py --include math --minify --output three-onlymath.min.js