source: data/branches/Shader_HS18/programs/Example/GLSLES/hdr_downscale3x3brightpass.glsles @ 12091

#version 100
precision mediump int;
precision mediump float;

uniform sampler2D inRTT;
uniform sampler2D inLum;
uniform vec2 texelSize;

varying vec2 uv;
const vec4 BRIGHT_LIMITER = vec4(0.6, 0.6, 0.6, 0.0);

const float MIDDLE_GREY = 0.72;
const float FUDGE = 0.001;
const float L_WHITE = 1.5;

/** Tone mapping function 
@note Only affects rgb, not a
@param inColour The HDR colour
@param lum The scene lumninence 
@returns Tone mapped colour
*/
vec4 toneMap(in vec4 inColour, in float lum)
{
        // From Reinhard et al
        // "Photographic Tone Reproduction for Digital Images"
        
        // Initial luminence scaling (equation 2)
    inColour.rgb *= MIDDLE_GREY / (FUDGE + lum);

        // Control white out (equation 4 nom)
    inColour.rgb *= (1.0 + inColour.rgb / L_WHITE);

        // Final mapping (equation 4 denom)
        inColour.rgb /= (1.0 + inColour.rgb);
        
        return inColour;
}

void main(void)
{
    vec4 accum = vec4(0.0, 0.0, 0.0, 0.0);

    accum += texture2D(inRTT, uv + texelSize * vec2(-1.0, -1.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 0.0, -1.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 1.0, -1.0));
    accum += texture2D(inRTT, uv + texelSize * vec2(-1.0,  0.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 0.0,  0.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 1.0,  0.0));
    accum += texture2D(inRTT, uv + texelSize * vec2(-1.0,  1.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 0.0,  1.0));
    accum += texture2D(inRTT, uv + texelSize * vec2( 1.0,  1.0));
    
        // take average of 9 samples
        accum *= 0.1111111111111111;

    // Reduce bright and clamp
    accum = max(vec4(0.0, 0.0, 0.0, 1.0), accum - BRIGHT_LIMITER);

        // Sample the luminence texture
        vec4 lum = texture2D(inLum, vec2(0.5, 0.5));
        
        // Tone map result
        gl_FragColor = toneMap(accum, lum.r);
}