// In our vertex shader, we need to add a new varying variable.
// I am going to call this texCoord, and it is a vec2:
// varying vec2 texCoord;

// I then need to assign some values to this variable. But first
// I will explain what this variable will do. This variable will
// hold the texture coordinates for the current vertex. The 
// texture coordinates for the teapot which is a predefined GLUT
// shape are already assigned in OpenGL by GLUT. So to read them 
// in, we use the line:
// texCoord = gl_MultiTexCoord0.xy
// gl_MultiTexCoord is generally used to store texture coordinates
// but some people like to store variables in this that will
// then be used for other means inside the shader. I am going
// to stick with using it for texture coordinates as it is
// simpler and less confusing. Also note that I am adding .xy
// to the end of gl_MultiTexCoord0, this is to call the
// first two parts of the variable because texCoord is only 
// a two part variable and gl_MultiTexCoord can hold 3D textures
// which could be called with .xyz.

varying vec2 texCoord;

varying vec3 Normal;
varying vec3 Light;
varying vec3 HalfVector;

void main(void)
{			
	texCoord = gl_MultiTexCoord0.xy

	Normal = normalize(gl_NormalMatrix * gl_Normal);

	Light = normalize(gl_LightSource[0].position.xyz);

	HalfVector = normalize(gl_LightSource[0].halfVector.xyz);

	gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}