用可编程渲染管线实现phone光照模型

Ambient Lighting = Ca*[Ga + sum(Atti*Spoti*Lai)] 

Diffuse Lighting = sum[Cd*Ld*(N.Ldir)*Atten*Spot]

float4x4 matViewProjection;
float4 Light_Position;
float4 Light_Attenuation;
float4 Light_Color;
float4 Ambient_Color;
float4 vViewPosition;
float alpha;
struct VS_INPUT 
{
  float4 Position : POSITION0;
  float3 Normal    : NORMAL0;
  float2 Texcoord : TEXCOORD0;
};
struct VS_OUTPUT 
{
  float4 Position : POSITION0;
  float2 Texcoord : TEXCOORD0;
  float4 Color     : COLOR0;
};
float4 PointLighting(float3 position, float3 normal
                    , float3 eyedir, float4 ambient
                   , float3 lightpos, float3 lightatt, float4 lightcolor)
{
 float3 lightdir = normalize(position - lightpos);
 float3 dis = distance(position, lightpos);
 float disatt = saturate(1 / ( lightatt.x + lightatt.y * dis + lightatt.z * dis * dis ));
 float angleatt = saturate(-lightdir * normal);
 float3 reflectdir = normalize(reflect(lightdir, normal));
 float specularatt = pow(saturate(reflectdir * eyedir), alpha);
 
    return ambient + lightcolor * disatt * (angleatt + specularatt);
}
VS_OUTPUT vs_main( VS_INPUT Input )
{
   VS_OUTPUT Output;
   Output.Position = mul( Input.Position, matViewProjection );
   Output.Texcoord = Input.Texcoord;
  float3 eyedir = normalize(vViewPosition - Input.Position);
   Output.Color = PointLighting(Input.Position, Input.Normal
                       , eyedir, Ambient_Color
                       , Light_Position, Light_Attenuation, Light_Color);
   return( Output );
  
}