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));
}