minetest/client/shaders/update_exposure/opengl_fragment.glsl
x2048 6d45c243f8
Add dynamic exposure correction (#12959)
* Add uniform for frame delta time
* Adjust exposure in logarithmic (EV) space
* Add network support and LUA API
* Add testing mod
2023-01-06 22:33:25 +01:00

76 lines
2.5 KiB
GLSL

#define exposure texture0
#define screen texture1
struct ExposureParams {
float luminanceMin;
float luminanceMax;
float exposureCorrection;
float luminanceKey;
float speedDarkBright;
float speedBrightDark;
float centerWeightPower;
float compensationFactor;
};
uniform sampler2D exposure;
uniform sampler2D screen;
#ifdef ENABLE_BLOOM
uniform float bloomStrength;
#else
const float bloomStrength = 1.0;
#endif
uniform ExposureParams exposureParams;
uniform float animationTimerDelta;
const vec3 luminanceFactors = vec3(0.213, 0.715, 0.072);
float getLuminance(vec3 color)
{
return dot(color, luminanceFactors);
}
void main(void)
{
float previousExposure = texture2D(exposure, vec2(0.5, 0.5)).r;
vec3 averageColor = vec3(0.);
float n = 0.;
// Scan the screen with center-weighting and sample average color
for (float _x = 0.1; _x < 0.9; _x += 0.17) {
float x = pow(_x, exposureParams.centerWeightPower);
for (float _y = 0.1; _y < 0.9; _y += 0.17) {
float y = pow(_y, exposureParams.centerWeightPower);
averageColor += texture2D(screen, vec2(0.5 + 0.5 * x, 0.5 + 0.5 * y)).rgb;
averageColor += texture2D(screen, vec2(0.5 + 0.5 * x, 0.5 - 0.5 * y)).rgb;
averageColor += texture2D(screen, vec2(0.5 - 0.5 * x, 0.5 + 0.5 * y)).rgb;
averageColor += texture2D(screen, vec2(0.5 - 0.5 * x, 0.5 - 0.5 * y)).rgb;
n += 4.;
}
}
float luminance = getLuminance(averageColor);
luminance /= n;
luminance /= pow(2., previousExposure) * bloomStrength * exposureParams.compensationFactor; // compensate for the configurable factors
luminance = clamp(luminance, exposureParams.luminanceMin, exposureParams.luminanceMax);
// From https://media.contentapi.ea.com/content/dam/eacom/frostbite/files/course-notes-moving-frostbite-to-pbr-v2.pdf
// 1. EV100 = log2(luminance * S / K) where S = 100, K = 0.125 = log2(luminance) + 3
// 2. Lmax = 1.2 * 2 ^ (EV100 - EC)
// => Lmax = 1.2 * 2^3 * luminance / 2^EC = 9.6 * luminance / 2^EC
// 3. exposure = 1 / Lmax
// => exposure = 2^EC / (9.6 * luminance)
float wantedExposure = exposureParams.exposureCorrection - log(luminance)/0.693147180559945 - 3.263034405833794;
if (wantedExposure < previousExposure)
wantedExposure = mix(wantedExposure, previousExposure, exp(-animationTimerDelta * exposureParams.speedDarkBright)); // dark -> bright
else
wantedExposure = mix(wantedExposure, previousExposure, exp(-animationTimerDelta * exposureParams.speedBrightDark)); // bright -> dark
gl_FragColor = vec4(vec3(wantedExposure), 1.);
}