// This is C8E4f_specSurf from "The Cg Tutorial" (Addison-Wesley, ISBN
// 0321194969) by Randima Fernando and Mark J. Kilgard.  See page 209.

float3 expand(float3 v) { return (v-0.5)*2; }

void C8E4f_specSurf(float2 normalMapTexCoord : TEXCOORD0,
                    float3 lightDirection    : TEXCOORD1,
                    float3 halfAngle         : TEXCOORD2,

                out float4 color : COLOR,

            uniform float  ambient,
            uniform float4 LMd, // Light-material diffuse
            uniform float4 LMs, // Light-material specular
            uniform sampler2D   normalMap,
            uniform samplerCUBE normalizeCube,
            uniform samplerCUBE normalizeCube2)
{
  // Fetch and expand range-compressed normal
  float3 normalTex = tex2D(normalMap, normalMapTexCoord).xyz;
  float3 normal = expand(normalTex);
  // Fetch and expand normalized light vector
  float3 normLightDirTex = texCUBE(normalizeCube,
                                   lightDirection).xyz;
  float3 normLightDir = expand(normLightDirTex);
  // Fetch and expand normalized half-angle vector
  float3 normHalfAngleTex = texCUBE(normalizeCube2,
                                    halfAngle).xyz;
  float3 normHalfAngle = expand(normHalfAngleTex);
 
  // Compute diffuse and specular lighting dot products
  float diffuse = saturate(dot(normal, normLightDir));
  float specular = saturate(dot(normal, normHalfAngle));
  // Successive multiplies to raise specular to 8th power
  float specular2 = specular*specular;
  float specular4 = specular2*specular2;
  float specular8 = specular4*specular4;

  color = LMd*(ambient+diffuse) + LMs*specular8;
}
