source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/sky_preetham.cg @ 2964

//--------------------------------------------------------------------------------------
// Input and Output structs
//--------------------------------------------------------------------------------------



struct VertexInput
{
        float4 position: POSITION;
        float3 normal: NORMAL;
        float3 color: COLOR;
        float2 texcoord: TEXCOORD0;
};


// vtx output
struct vtxout
{
        float4 position: POSITION; // eye space
        float4 texCoord: TEXCOORD0;    

        float4 color: COLOR0;  
        float4 worldPos: TEXCOORD1; // world position
        float3 normal: TEXCOORD2;
        float4 mypos: TEXCOORD3;
};



struct pixel
{
  float4 col: COLOR0;
  float4 pos: COLOR1;
  float4 norm: COLOR2;
};

// fragment input
struct fragin
{
        float4 color: COLOR0;  
        float4 position: POSITION; // eye space
        float4 texCoord: TEXCOORD0;    

        float4 projPos: WPOS;
        float4 worldPos: TEXCOORD1; // world position
        float3 normal: TEXCOORD2;
        float4 mypos: TEXCOORD3;
};
//--------------------------------------------------------------------------------------
// Vertex Shaders
//--------------------------------------------------------------------------------------


vtxout default_vs(VertexInput IN,
                                  uniform float3 lightDir,
                                  uniform float2 thetaSun,
                                  uniform float3 zenithColor,
                                  uniform float3 aColor,
                                  uniform float3 bColor,
                                  uniform float3 cColor,
                                  uniform float3 dColor,
                                  uniform float3 eColor,
                                  uniform float4x4 ModelView)
{
        vtxout OUT;

        OUT.position = mul(glstate.matrix.mvp, IN.position);


        const float dotLN = dot(lightDir, IN.normal);   
        const float cos2gamma = dotLN * dotLN; 

        const float gamma = acos(dotLN);    
        const float theta = dot(float3(0.0, 0.0, 1.0), IN.normal);

    float3 num = (1.0 + aColor * exp(bColor / theta)) * (1.0 + cColor * exp(dColor * gamma) + eColor * cos2gamma);    
        float3 den = (1.0 + aColor * exp(bColor)) * (1.0 + cColor * exp(dColor * thetaSun.x) + eColor * thetaSun.y);   
    float3 xyY = (num / den) * zenithColor;    
    
    float3 XYZ;                                                                                             
                                                                                                            
    XYZ.x = (xyY.x / xyY.y) * xyY.z;                                                                        
        XYZ.y = xyY.z;                                                                                          
        XYZ.z = ((1.0f - xyY.x - xyY.y) / xyY.y) * xyY.z;   
        
    const static float3x3 conv_Mat = 
                float3x3(3.240479, -1.537150, -0.498535,
                         -0.969256, 1.875992,  0.041556,
                             0.055648, -0.204043,  1.057311);

        float3 hcol = mul(conv_Mat, XYZ);
        OUT.color = float4(hcol, 1.0);

        OUT.color.rgb *= 5e-5f; 

        //OUT.worldPos = mul(glstate.matrix.inverse.projection, OUT.position);
        OUT.worldPos = mul(ModelView, IN.position);

        OUT.normal = IN.normal;
        OUT.mypos = OUT.position;

        return OUT;
}


pixel frag_skydome(fragin IN)
{
        pixel pix;

        pix.col = IN.color;
        pix.pos = IN.worldPos * 1e20;// * maxDepth;

        pix.norm.xyz = IN.normal;
        
        // hack: squeeze some information about the ambient term into the target
        pix.norm.w = 1;
        pix.pos.w = IN.mypos.w;
        
        // the projected depth
        pix.col.w = IN.mypos.z / IN.mypos.w;

        return pix;
}