// data from application to vertex program
struct vertexIn {
   float3 Position : POSITION;    // pre-defined registers
   float4 UV :       TEXCOORD0;
   float4 Normal :   NORMAL;
};
// vertex shader to pixel shader
struct vertexOut {
   float4 HPosition :   POSITION;
   float4 TexCoord :    TEXCOORD0;
   float3 LightVec :    TEXCOORD1;
   float3 WorldNormal : TEXCOORD2;
   float3 WorldPos :    TEXCOORD3;
   float3 WorldView :   TEXCOORD4;
};

// vertex shader
vertexOut mainVS(vertexIn IN,      // vertex input from app
      uniform float4x4 WorldViewProj,// constant parameters
      uniform float4x4 WorldIT,      // from app: various
      uniform float4x4 World,        // transformation
      uniform float4x4 ViewIT,       // matrices and a
      uniform float3 LightPos        // point-light source
      )
{
   vertexOut OUT; // output of the vertex shader
   OUT.WorldNormal = mul(WorldIT, IN.Normal).xyz;
   // position in object coords:
   float4 Po = float4(IN.Position.x,IN.Position.y,
         IN.Position.z,1.0);
   float3 Pw = mul(World, Po).xyz; // pos in world coord


   OUT.WorldPos = Pw;             // pos in world coords
   OUT.LightVec = LightPos - Pw; // light vector
   OUT.TexCoord = IN.UV;          // original tex coords
   // view vector in world coords:
   OUT.WorldView = normalize(ViewIT[3].xyz - Pw);
   // pos in clip coords:
   OUT.HPosition = mul(WorldViewProj, Po);
   return OUT;                 // output of vertex shader
}