Tiny Example Vertex & Fragment Shader programs
   Orion Sky Lawlor, olawlor@acm.org, 2005/2/9 (Public Domain)

Building:
  On a Linux machine with the GLUT libraries, you should be able
  to type "make" and get a "main" executable.  Anywhere else,
  you should be able to just compile "main.cpp" to get "main".

Running:
  The fragment shader is loaded from "fragment.txt" every frame,
  so if you change fragment.txt while the program is running, 
  it will immediately begin displaying the new version (as soon
  as the window is redrawn).  The vertex shader is loaded from
  "vertex.txt".  

  The default OpenGL vertex shader does *nothing*, not even
  transform the vertex position into clip coordinates; I always
  use a vertex shader that does this, plus sets up fragment.texcoord
  4-7 to contain the world-coordinates position, normal, color,
  and eye direction.  These are the basics you need to do any sort
  of shading and lighting computation; and you can use the same
  vertex shader for everything.