source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/sky_preetham.cg @ 3009

//--------------------------------------------------------------------------------------
// 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;
        float4 color2: TEXCOORD4;
};


struct pixel
{
        float4 col: COLOR0;
        float4 norm: COLOR1;
        float3 pos: 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;
        float4 color2: TEXCOORD4;
};
//--------------------------------------------------------------------------------------
// 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,
                                  uniform float multiplier)
{
        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 *= multiplier;

        OUT.color2 = OUT.color;
        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.color2;
        pix.col.w = 1e20f;

        pix.norm.xyz = IN.normal;
        pix.norm.w = IN.mypos.w;

        //pix.pos = 1e20f;
        
        return pix;
}