varying vec3 N;
varying vec3 v;
varying float ambient_occlusion_term;

void main (void)  
{  
   vec3 L = normalize(gl_LightSource[0].position.xyz);   
   vec3 E = normalize(-v);
   vec3 R = normalize(-reflect(L,N));
 
   //calculate Ambient Term:  
   vec4 Iamb = gl_LightSource[0].ambient;    

   //calculate Diffuse Term:  
   vec4 Idiff = gl_LightSource[0].diffuse * max(dot(N,L), 0.0);    
   
   // calculate Specular Term:
   vec4 Ispec = gl_LightSource[0].specular 
                * pow(max(dot(R,E),0.0),0.3*gl_FrontMaterial.shininess);

   // write Total Color:  
   // Without GL_COLOR_MATERIAL
   //vec4 color = gl_FrontLightModelProduct.sceneColor + Iamb + Idiff + Ispec;   
   // With GL_COLOR_MATERIAL ??
   vec4 theColor = vec4(gl_Color);
   vec4 color = (gl_FrontMaterial.emission + 1.5*theColor* Iamb + 1.2*theColor* Idiff + Ispec);
   color.a = gl_Color.a;

   float fogFactor = (gl_Fog.end - gl_FogFragCoord)*gl_Fog.scale;
   fogFactor = clamp(fogFactor,0.0,1.0);
   gl_FragColor = mix(gl_Fog.color, color, fogFactor );
   // This is for the future.
   //gl_FragColor.rgb *= ambient_occlusion_term;
   
}