source: GTP/branches/IllumWPdeliver2008dec/IlluminationWP/demos/OgreGames/MoriaBattle/Media/MORIA/MoriaDust.hlsl @ 3255

struct SBB_VS_OUT
{
        float4 hPosition        : POSITION;
        float4 texCoord         : TEXCOORD0;
        float3 P                : TEXCOORD1;
        float3 Q                : TEXCOORD2;
        float r                 : TEXCOORD3;
        float2 screenCoord      : TEXCOORD4;    
        float4 color            : COLOR0;
};

SBB_VS_OUT MoriaDust_VS (float4 position : POSITION,    
                float4 texCoord : TEXCOORD0,
                float4 color    : COLOR,
                uniform float width,
                uniform float height,
                uniform float4x4 worldView,
                uniform float4x4 Proj)
{
        SBB_VS_OUT OUT;
 ///transform to camera space and create a sprite with vertex offset 
        float2 offset = texCoord.zw;
        float4 cPosition;   
        float4 wPosition = position;    
        cPosition = mul(worldView, wPosition);
/// P is the particle sphere center     
        OUT.P = cPosition.xyz;
        OUT.P.z = - 1 * OUT.P.z;
        cPosition.xy += offset;
/// Q is the shaded point (it is moved backwards to avoid unwanted frontplane clipping)                         
        OUT.Q = cPosition.xyz;  
        OUT.Q.z = OUT.P.z;
        OUT.r = abs(texCoord.z);   
/// calculate screen space position 
   OUT.hPosition = mul( Proj, cPosition );
   OUT.screenCoord =  (OUT.hPosition.xy / OUT.hPosition.w + 1.0) / 2.0;
   OUT.screenCoord.y = 1.0 - OUT.screenCoord.y;
   OUT.screenCoord += float2(0.5/width, 0.5/height);   
   
   OUT.texCoord = texCoord;
   OUT.color = color;

  return OUT;
} 


float4 MoriaDust_PS(SBB_VS_OUT IN ,
        //      in screenCoord : VPOS,
            uniform float nearplane,
            uniform float farplane,
            uniform float4 lightCPos,
            uniform float lightPower,
        uniform float4 color,
        uniform float symmetry,
            uniform sampler2D colorTexture : register(s0),
            uniform sampler2D DepthMap : register(s1),
            uniform sampler2D PhaseMap : register(s2)
           ) : COLOR
{
        float4 Color = IN.color * color;
        float alpha = 0;
        
/// get the depth values from the depthMap and calculate ray length in sphere   
        float d = length( IN.Q - IN.P );
        float Zs;
        if( d < IN.r )
        {
         
         float w = sqrt( IN.r * IN.r - d * d );
         alpha = w / IN.r;
         alpha *= pow( (IN.r-d) / IN.r , 2);
        
         float F = IN.Q.z - w;
         float B = IN.Q.z + w; 
         

         Zs = tex2D( DepthMap, IN.screenCoord ).r;
         if(Zs == 0) Zs = farplane;
         float ds = min( Zs, B ) - max( nearplane, F );  
        // float ds = min( Zs, B ) - F;  
         alpha *=  ds / w * 0.5;
        }
/// fetch opacity from a texture
        Color.a *= tex2D( colorTexture, IN.texCoord.xy).r;
        Color.a *= alpha;
        
        //illumination
        lightCPos.z *= -1;
        float2 L = lightCPos.xy - IN.Q.xy;
        float ld = length(L);
        L = L / ld;
        float3 V = normalize(-IN.Q);
        float phase;// = /*lightPower / (ld*ld) * */tex2D(PhaseMap, float2(symmetry, dot(L,V)) * 0.5 + 0.5).r;
//      float phase = (dot(L, V) + 1.0) * 0.5;

        float ld2 = max(0.01, ld * ld);
        phase = lightPower / ld2;
        //Color.rgb *= phase;
        return Color; 
}