source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/tonemap.cg @ 2973

#include "../shaderenv.h"


struct fragment
{
         // normalized screen position
        float4 pos: WPOS;
        float4 texCoord: TEXCOORD0; 

        float2 lt: TEXCOORD1; // left top
        float2 rb: TEXCOORD2; // right bottom
        float2 rt: TEXCOORD3; // right top
        float2 lb: TEXCOORD4; // left bottom
};


struct pixel
{
        float4 col: COLOR0;
};


float4 DownSample(fragment IN,
                                  uniform sampler2D colors,
                                  float2 downSampleOffs[16]) : COLOR
{    
    float4 average = .0f;

    for(int i = 0; i < 16; ++ i)
    {
        average += tex2D(colors, IN.texCoord.xy + downSampleOffs[i]);
    }
        
    average *= 1.0f / 16.0f;

    return average;
}
    

float4 GreyScaleDownSample(fragment IN,
                                                   uniform sampler2D colors): COLOR
{

        // Compute the average of the 4 necessary samples
        float average = 0.0f;
        float maximum = -1e20;

        // the rgb weights
        const float3 w = float3(0.299f, 0.587f, 0.114f);
        //float3 w = float3(0.2125f, 0.7154f, 0.0721f);

        float4 cols[4];

        cols[0] = tex2D(colors, IN.texCoord.xy + IN.lt.xy);
        cols[1] = tex2D(colors, IN.texCoord.xy + IN.lb.xy);
        cols[2] = tex2D(colors, IN.texCoord.xy + IN.rt.xy);
        cols[3] = tex2D(colors, IN.texCoord.xy + IN.rb.xy);


        for (int i = 0; i < 4; ++ i)
        {
                const float intensity = dot(cols[i].rgb, w);

                maximum = max(maximum, intensity);
                average += (0.25f * log(1e-5f + intensity));
        }

        average = exp(average);

        return tex2D(colors, IN.texCoord.xy);

        // Output the luminance to the render target
        return float4(average, maximum, 0.0f, 1.0f);
}
    

pixel ToneMap(fragment IN,
                          uniform sampler2D colors,
                          uniform float imageKey, 
                          uniform float whiteLum, 
                          uniform float middleGrey)
{
        pixel OUT;
        float4 color = tex2D(colors, IN.texCoord.xy);

        const float pixLum = 0.2125f * color.x + 0.7154f * color.y + 0.0721f * color.z;
        
        // adjust to middle gray
        const float lum = middleGrey * pixLum / imageKey;
         
        // map to range and calc burnout
        const float scaleLum = lum * (1.0f + lum / whiteLum * whiteLum) / (1.0f + lum);

        OUT.col = color * scaleLum / pixLum;
        OUT.col.w = color.w;

        return OUT;
}