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improve time of day transition quality by using Oklab and smoothstep #509

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Merged
nschimme merged 1 commit into from
Apr 8, 2026
Merged

improve time of day transition quality by using Oklab and smoothstep #509

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16 changes: 7 additions & 9 deletions src/resources/shaders/legacy/weather/atmosphere/frag.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -67,14 +67,12 @@ void main()
float uCloudsIntensity = mix(uIntensities[2], uTargets[2], weatherLerp);
float uFogIntensity = mix(uIntensities[3], uTargets[3], weatherLerp);

float timeOfDayLerp = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration,
0.0,
1.0);
float tTod = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration, 0.0, 1.0);
float timeOfDayLerp = smoothstep(0.0, 1.0, tTod);
float currentTimeOfDayIntensity = mix(uTimeOfDay.z, uTimeOfDay.w, timeOfDayLerp);
vec4 timeOfDayStart = uNamedColors[int(uTimeOfDay.x)];
vec4 timeOfDayTarget = uNamedColors[int(uTimeOfDay.y)];
vec4 uTimeOfDayColor = mix(timeOfDayStart, timeOfDayTarget, timeOfDayLerp);
uTimeOfDayColor.a *= currentTimeOfDayIntensity;
float alphaStart = uNamedColors[int(uTimeOfDay.x)].a;
float alphaTarget = uNamedColors[int(uTimeOfDay.y)].a;
float uTimeOfDayAlpha = mix(alphaStart, alphaTarget, timeOfDayLerp) * currentTimeOfDayIntensity;

// Atmosphere overlay is now transparent by default (TimeOfDay is drawn separately)
vec4 result = vec4(0.0);
Expand All @@ -86,7 +84,7 @@ void main()
float density = 0.4 + uFogIntensity * 0.4;
vec4 fog = vec4(0.8, 0.8, 0.85, uFogIntensity * n * localMask * density);
// Emissive boost at night
fog.rgb += uTimeOfDayColor.a * 0.15;
fog.rgb += uTimeOfDayAlpha * 0.15;

// Blend fog over result
float combinedAlpha = 1.0 - (1.0 - result.a) * (1.0 - fog.a);
Expand All @@ -106,7 +104,7 @@ void main()
1.0 * storminess,
uCloudsIntensity * puffy * localMask * 0.5);
// Emissive boost at night
clouds.rgb += uTimeOfDayColor.a * 0.1;
clouds.rgb += uTimeOfDayAlpha * 0.1;

// Blend clouds over result
float combinedAlpha = 1.0 - (1.0 - result.a) * (1.0 - clouds.a);
Expand Down
16 changes: 7 additions & 9 deletions src/resources/shaders/legacy/weather/particle/frag.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -40,29 +40,27 @@ void main()
float pIntensity = max(pRain, pSnow);
float pType = pSnow / max(pIntensity, 0.001);

float timeOfDayLerp = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration,
0.0,
1.0);
float tTod = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration, 0.0, 1.0);
float timeOfDayLerp = smoothstep(0.0, 1.0, tTod);
float currentTimeOfDayIntensity = mix(uTimeOfDay.z, uTimeOfDay.w, timeOfDayLerp);
vec4 timeOfDayStart = uNamedColors[int(uTimeOfDay.x)];
vec4 timeOfDayTarget = uNamedColors[int(uTimeOfDay.y)];
vec4 uTimeOfDayColor = mix(timeOfDayStart, timeOfDayTarget, timeOfDayLerp);
uTimeOfDayColor.a *= currentTimeOfDayIntensity;
float alphaStart = uNamedColors[int(uTimeOfDay.x)].a;
float alphaTarget = uNamedColors[int(uTimeOfDay.y)].a;
float uTimeOfDayAlpha = mix(alphaStart, alphaTarget, timeOfDayLerp) * currentTimeOfDayIntensity;

float lifeFade = smoothstep(0.0, 0.15, vLife) * smoothstep(1.0, 0.85, vLife);

// Rain visuals
float streak = 1.0 - smoothstep(0.0, 0.15, abs(vLocalCoord.x - 0.5));
float rainAlpha = mix(0.4, 0.7, clamp(pIntensity, 0.0, 1.0));
vec4 rainColor = vec4(0.6, 0.6, 1.0, pIntensity * streak * vLocalMask * rainAlpha * lifeFade);
rainColor.rgb += uTimeOfDayColor.a * 0.2;
rainColor.rgb += uTimeOfDayAlpha * 0.2;

// Snow visuals
float dist = distance(vLocalCoord, vec2(0.5));
float flake = 1.0 - smoothstep(0.1, 0.2, dist);
float snowAlpha = mix(0.6, 0.9, clamp(pIntensity, 0.0, 1.0));
vec4 snowColor = vec4(1.0, 1.0, 1.1, pIntensity * flake * vLocalMask * snowAlpha * lifeFade);
snowColor.rgb += uTimeOfDayColor.a * 0.3;
snowColor.rgb += uTimeOfDayAlpha * 0.3;

// Interpolate visuals based on pType
vec4 pColor = mix(rainColor, snowColor, pType);
Expand Down
72 changes: 64 additions & 8 deletions src/resources/shaders/legacy/weather/timeofday/frag.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -23,22 +23,78 @@ layout(std140) uniform WeatherBlock

out vec4 vFragmentColor;

vec3 srgbToLinear(vec3 c)
{
vec3 low = c / 12.92;
vec3 high = pow((c + 0.055) / 1.055, vec3(2.4));
return mix(low, high, step(vec3(0.04045), c));
}

vec3 linearToSrgb(vec3 c)
{
vec3 low = c * 12.92;
vec3 high = 1.055 * pow(c, vec3(1.0 / 2.4)) - 0.055;
return mix(low, high, step(vec3(0.0031308), c));
}

vec3 linearToOklab(vec3 c)
{
float l = 0.4122214708 * c.r + 0.5363325363 * c.g + 0.0514459929 * c.b;
float m = 0.2119034982 * c.r + 0.6806995451 * c.g + 0.1073969566 * c.b;
float s = 0.0883024619 * c.r + 0.2817188376 * c.g + 0.6299787005 * c.b;

float l_ = pow(l, 1.0 / 3.0);
float m_ = pow(m, 1.0 / 3.0);
float s_ = pow(s, 1.0 / 3.0);

return vec3(0.2104542553 * l_ + 0.7936177850 * m_ - 0.0040720403 * s_,
1.9779984951 * l_ - 2.4285922050 * m_ + 0.4505937099 * s_,
0.0259040371 * l_ + 0.7827717662 * m_ - 0.8086757660 * s_);
}

vec3 oklabToLinear(vec3 c)
{
float l_ = c.x + 0.3963377774 * c.y + 0.2158037573 * c.z;
float m_ = c.x - 0.1055613458 * c.y - 0.0638541728 * c.z;
float s_ = c.x - 0.0894841775 * c.y - 1.2914855480 * c.z;

float l = l_ * l_ * l_;
float m = m_ * m_ * m_;
float s = s_ * s_ * s_;

return vec3(4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s,
-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s,
-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s);
}

void main()
{
float uCurrentTime = uTime.x;
float uTimeOfDayStartTime = uConfig.y;
float uTransitionDuration = uConfig.z;

vec4 timeOfDayStart = uNamedColors[int(uTimeOfDay.x)];
vec4 timeOfDayTarget = uNamedColors[int(uTimeOfDay.y)];
vec4 timeOfDayStartSrgb = uNamedColors[int(uTimeOfDay.x)];
vec4 timeOfDayTargetSrgb = uNamedColors[int(uTimeOfDay.y)];

float t = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration, 0.0, 1.0);
float timeOfDayLerp = smoothstep(0.0, 1.0, t);

// Convert start and target colors to Oklab
vec3 startOklab = linearToOklab(srgbToLinear(timeOfDayStartSrgb.rgb));
vec3 targetOklab = linearToOklab(srgbToLinear(timeOfDayTargetSrgb.rgb));

// Interpolate in Oklab space
vec3 mixedOklab = mix(startOklab, targetOklab, timeOfDayLerp);

// Convert back to sRGB
vec3 mixedSrgb = linearToSrgb(oklabToLinear(mixedOklab));
Comment on lines +89 to +90

@sourcery-ai sourcery-ai Bot Apr 7, 2026

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suggestion (bug_risk): Consider clamping the final sRGB color to avoid out-of-gamut values from Oklab interpolation.

Oklab interpolation can yield linear RGB outside [0, 1], which converts to out-of-gamut sRGB. If the pipeline isn’t intentionally handling HDR/overbright values, consider clamping the final sRGB result, e.g.:

vec3 mixedSrgb = clamp(linearToSrgb(oklabToLinear(mixedOklab)), 0.0, 1.0);

This avoids artifacts in later stages that assume normalized color channels.

Suggested change
// Convert back to sRGB
vec3 mixedSrgb = linearToSrgb(oklabToLinear(mixedOklab));
// Convert back to sRGB and clamp to valid [0, 1] range to avoid out-of-gamut values
vec3 mixedSrgb = clamp(linearToSrgb(oklabToLinear(mixedOklab)), 0.0, 1.0);


float timeOfDayLerp = clamp((uCurrentTime - uTimeOfDayStartTime) / uTransitionDuration,
0.0,
1.0);
// Mix intensity with smoothstep as well
float currentTimeOfDayIntensity = mix(uTimeOfDay.z, uTimeOfDay.w, timeOfDayLerp);

vec4 uTimeOfDayColor = mix(timeOfDayStart, timeOfDayTarget, timeOfDayLerp);
uTimeOfDayColor.a *= currentTimeOfDayIntensity;
// Final color with alpha
float finalAlpha = mix(timeOfDayStartSrgb.a, timeOfDayTargetSrgb.a, timeOfDayLerp);
finalAlpha *= currentTimeOfDayIntensity;

vFragmentColor = uTimeOfDayColor;
vFragmentColor = vec4(mixedSrgb, finalAlpha);
}
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