//
// Simple Vertex Program
//
// - Calculates simple diffuse and specular
//

// Define 'vendor-specific' diffuse color ;)
float3 diffuseColor = float3(0.8, 1, 0.1); // NVidia
//float3 diffuseColor = float3(1.0, 0.0, 0.0); // ATI

// Define white specular color
float3 specularColor = float3(1.0, 1.0, 1.0);

// Define inputs from application
struct appin
{
    float4 Position  : POSITION;
    float4 Normal    : NORMAL;
};

// Define outputs from vertex shader
struct vertout
{
    float4 HPosition : POSITION;
    float4 Color     : COLOR;
};

vertout main(appin IN,
             uniform float4x4 ModelViewProj,
             uniform float4x4 ModelViewIT,
             uniform float4 LightVec)
{
  vertout OUT;

  // Transform vertex position into homogenous clip-space.
  OUT.HPosition = mul(ModelViewProj, IN.Position);

  // Transform normal from model-space to view-space.
  float3 normalVec = normalize(mul(ModelViewIT, IN.Normal).xyz);

  // Store normalized light vector.
  float3 lightVec = normalize(LightVec.xyz);

  // Calculate half angle vector.
  float3 eyeVec = float3(0.0, 0.0, 1.0);
  float3 halfVec = normalize(lightVec + eyeVec);

  // Calculate diffuse component.
  float diffuse = dot(normalVec, lightVec);

  // Calculate specular component.
  float specular = dot(normalVec, halfVec);

  // Use the lit function to compute lighting vector from
  // diffuse and specular values.
  float4 lighting = lit(diffuse, specular, 32);

  // Combine diffuse and specular contributions and
  // output final vertex color.
  OUT.Color.rgb = lighting.y * diffuseColor +
                  lighting.z * specularColor;
  OUT.Color.a = 1.0;

  return OUT;
}