title: quaternion libraries in C/C++
body: <p>Any good libraries for <em>quaternion</em> calculations in C/C++ ? </p>
  
  <p>Side note: any good tutorials/examples? I've google it and been to the first few pages but maybe you have have some demos/labs from compsci or math courses you could/would share? </p>
  
  <p>Thanks</p>