vec3 uncharted2Tonemap(const vec3 x) {
	const float A = 0.15;
	const float B = 0.50;
	const float C = 0.10;
	const float D = 0.20;
	const float E = 0.02;
	const float F = 0.30;
	return ((x * (A * x + C * B) + D * E) / (x * (A * x + B) + D * F)) - E / F;
}

vec3 tonemapUncharted2(const vec3 color) {
	const float W = 11.2;
	const float exposureBias = 2.0;
	vec3 curr = uncharted2Tonemap(exposureBias * color);
	vec3 whiteScale = 1.0 / uncharted2Tonemap(vec3(W));
	return curr * whiteScale;
}

// Based on Filmic Tonemapping Operators http://filmicgames.com/archives/75
vec3 tonemapFilmic(const vec3 color) {
	vec3 x = max(vec3(0.0), color - 0.004);
	return (x * (6.2 * x + 0.5)) / (x * (6.2 * x + 1.7) + 0.06);
}

// https://knarkowicz.wordpress.com/2016/01/06/aces-filmic-tone-mapping-curve/
vec3 acesFilm(const vec3 x) {
    const float a = 2.51;
    const float b = 0.03;
    const float c = 2.43;
    const float d = 0.59;
    const float e = 0.14;
    return clamp((x * (a * x + b)) / (x * (c * x + d ) + e), 0.0, 1.0);
}

vec3 tonemapReinhard(const vec3 color) {
	return color / (color + vec3(1.0));
}

// Blender AgX Implementation 
// Troy Sobotka https://github.com/sobotka/AgX

// AGX Simple
vec3 tonemapAgXSimple(vec3 x) {
	// TODO CORRECT AND OPTIMIZE
    x = max(x, vec3(0.0));
    float exposure = 0.6;
    x *= exposure;
    const vec3 AgX_A = vec3(0.92, 0.92, 0.72);
    const vec3 AgX_B = vec3(0.24, 0.24, 0.36);
    const vec3 AgX_C = vec3(0.92, 0.92, 0.72);
    const vec3 AgX_D = vec3(0.24, 0.24, 0.36);
    const vec3 AgX_E = vec3(0.08, 0.08, 0.12);
    const vec3 AgX_F = vec3(0.0);
    vec3 result = (x * (AgX_A * x + AgX_B)) / (x * (AgX_C * x + AgX_D) + AgX_E) + AgX_F;
    float luma = dot(result, vec3(0.2126, 0.7152, 0.0722));
    result = mix(vec3(luma), result, 0.6);
    return clamp(result, vec3(0.0), vec3(1.0));
}

// AGX Full Contrast Approx
vec3 agxDefaultContrastApprox(vec3 x) {
    vec3 x2 = x * x;
    vec3 x4 = x2 * x2;
    return + 15.5     * x4 * x2
           - 40.14    * x4 * x
           + 31.96    * x4
           - 6.868    * x2 * x
           + 0.4298   * x2
           + 0.1191   * x
           - 0.00232;
}
// AGX Full Look
vec3 agxLook(vec3 x, float strength) {
    const vec3 slope = vec3(1.0);
    const vec3 power = vec3(1.35);
    const vec3 sat = vec3(1.4);
    vec3 lw = vec3(0.2126, 0.7152, 0.0722);
    float luma = dot(x, lw);
    return pow(x * slope, power) * sat - (pow(luma * slope, power) * (sat - 1.0));
}

// AGX Full
vec3 tonemapAgXFull(vec3 x) {
    // x *= 2.0 * (1.0/0.8); // Brightness scale to match Blender's default
    x = clamp(x, 0.0, 65504.0);
    x = log2(x + 1.0);
    x = agxDefaultContrastApprox(clamp(x * 0.5 - 10.5, -12.0, 12.0));    
    x = mix(x, agxLook(x, 0.5), 0.5);
    x = clamp(x, 0.0, 1.0);
    return pow(x, vec3(1.0/2.2)); 
}