// final pixel output:
// data from pixel shader to frame buffer
struct vertexOut {
   float4 HPosition :   POSITION;
   float4 TexCoord :    TEXCOORD0;
   float3 LightVec :    TEXCOORD1;
   float3 WorldNormal : TEXCOORD2;
   float3 WorldPos :    TEXCOORD3;
   float3 WorldView :   TEXCOORD4;
};

struct pixelOut {
   float4 col : COLOR;
};

// pixel shader
pixelOut main(vertexOut IN // input from vertex shade
      //uniform float SpecExpon,   // constant parameters fro
      //uniform float4 AmbiColor, // application
      //uniform float4 SurfColor,
      //uniform float4 LightColor
      )
{
   float SpecExpon = 120;
   float4 LightColor = { 1, 1, 1, 1 };

   pixelOut OUT;   // output of the pixel shader
   float3 Ln = normalize(IN.LightVec);
   float3 Nn = normalize(IN.WorldNormal);
   float3 Vn = normalize(IN.WorldView);
   float3 Hn = normalize(Vn + Ln);
   // scalar product between light and normal vectors:
   float ldn = dot(Ln,Nn);
   // scalar product between halfway and normal vectors:
   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;
   // sum of diffuse and specular contributions:
   float4 result = diffContrib + specContrib;
   OUT.col = result;
   return OUT;         // output of pixel shader
}