source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/tonemap.cg @ 3005

#include "../shaderenv.h"


struct frag
{
         // normalized screen position
        float2 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(frag IN,
                                  uniform sampler2D colors,
                                  uniform float2 downSampleOffs[4]): COLOR
{    
    float4 average = .0f;

    for(int i = 0; i < 4; ++ i)
    {
        average += tex2D(colors, IN.texCoord + downSampleOffs[i]);
    }
        
    average *= 1.0f / 4.0f;

    return tex2D(colors, IN.texCoord);//average;
}
    

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

        // Compute the average of the 4 necessary samples
        float average = .0f;
        float maximum = .0f;

        // 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.lt);
        cols[1] = tex2D(colors, IN.lb);
        cols[2] = tex2D(colors, IN.rt);
        cols[3] = tex2D(colors, IN.rb);

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

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

        average = exp(average * 0.25f);

        float4 hcols = cols[0] + cols[1] + cols[2] + cols[3];

        return hcols * 0.25f;
        //return float4(average, maximum, 0.0f, cols[0].w);

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

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

        const float pixLum = 0.2125f * color.x + 0.7154f * color.y + 0.0721f * color.z;
        
        // obtain new image key from highest mipmap level
        float logLumScaled = tex2Dlod(colors, float4(.5f, .5f, 0, 99)).w;
        float logLum = logLumScaled * LOGLUM_RANGE + MINLOGLUM;

        float newImageKey = exp(logLum);

        // adjust to middle gray
        const float lum = middleGrey * pixLum / newImageKey;
         
        // 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;
}


pixel CalcAvgLogLum(frag IN, uniform sampler2D colors)
{
        ////////////
        //-- write out logaritmic luminance for tone mapping

        pixel OUT;

        float4 color = tex2Dlod(colors, float4(IN.texCoord.xy, 0, 0));

        OUT.col = color;

        // the old loglum is stored in the hightest mipmap-level
        float oldLogLum = tex2Dlod(colors, float4(IN.texCoord.xy, 0, MAX_LOD_LEVEL)).w;

        // the intensity weights
        const float3 w = float3(0.299f, 0.587f, 0.114f);

        float lum = dot(color.rgb, w);
        float logLum = log(1e-5f + lum);

        float logLumOffset = MINLOGLUM * INV_LOGLUM_RANGE;
        float logLumScaled = logLum * INV_LOGLUM_RANGE - logLumOffset;

        if (oldLogLum > 1e-5f) // too bright
                OUT.col.w = lerp(oldLogLum, logLumScaled, 0.1f);
        else
                OUT.col.w = logLumScaled;

        return OUT;
}