struct vertexOut {
   float4 HPosition   : POSITION;
   float4 TexCoord    : TEXCOORD0;
   float3 LightVec    : TEXCOORD1;
   float3 EyeVec      : TEXCOORD2;
   float3 WorldNormal : TEXCOORD3;
};

struct pixelOut {
   float4 col : COLOR;
};

pixelOut main(vertexOut IN)
{
   pixelOut OUT;   // output of the pixel shader

   float SpecExpon = 120;
   float4 LightColor = { 1, 1, 1, 1 };

   float3 Ln = IN.LightVec;
   float3 Nn = IN.WorldNormal;
   float3 Vn = IN.EyeVec;

   float3 Hn = 0.5 * (Ln + Vn);
   float ldn = dot (Ln, Nn);
   float hdn = dot (Hn, Nn);

   // specialized "lit" function computes weights for
   // diffuse and specular parts:
   float4 litV = lit (ldn, hdn, SpecExpon);
   float4 diffContrib = glstate.material.diffuse * (litV.y * LightColor + glstate.lightmodel.ambient);
   float4 specContrib = litV.y * litV.z * LightColor;
   float4 result = diffContrib + specContrib;

   OUT.col = result;
   return OUT;         // output of pixel shader
}