This is a simple GLUT-based example that shows how to use igl's trackball.h
function.

To compile:
  make

Usage:
  ./example
or
  ./example [positive speed factor]

Interaction:
  Drag on screen to use trackball
  Press SPACE to change shape

Example #1:
  # use a speed factor of 2: twice as fast trackball
  ./example 2