weather: add lightning flashes during storms

config.js

@@ -136,9 +136,17 @@ window.CONFIG = {
             intensity: 1.0,
             maxAlpha: 0.45,
             speed: 0.35           // slow drifting flakes
+        },
+        lightning: {
+            enabled: true,
+            gain: 1.2,            // brightness of one flash
+            minDelayS: 8,         // minimum delay between storm flashes
+            maxDelayS: 45,        // maximum delay between storm flashes
+            doubleFlash: true     // some flashes flicker twice
         }
         // weatherEffects: { enabled: false }
         // weatherEffects: { rain: { maxAlpha: 0.55, speed: 1.4 }, snow: { enabled: false } }
+        // weatherEffects: { lightning: { gain: 2.0, minDelayS: 3, maxDelayS: 12 } }
     },
 
     // ------------------------------------------------------------------

vendor/clouds3d.js

@@ -6034,6 +6034,46 @@ var WEATHER_RAIN_ALPHA = (typeof WEATHER_RAIN_CFG.maxAlpha === 'number') ? Math.
 var WEATHER_SNOW_ALPHA = (typeof WEATHER_SNOW_CFG.maxAlpha === 'number') ? Math.max(0, Math.min(1, WEATHER_SNOW_CFG.maxAlpha)) : 0.45;
 var WEATHER_RAIN_SPEED = (typeof WEATHER_RAIN_CFG.speed === 'number') ? Math.max(0.1, WEATHER_RAIN_CFG.speed) : 1.0;
 var WEATHER_SNOW_SPEED = (typeof WEATHER_SNOW_CFG.speed === 'number') ? Math.max(0.05, WEATHER_SNOW_CFG.speed) : 0.35;
+var WEATHER_LIGHTNING_CFG = WEATHER_FX_CFG.lightning || {};
+var WEATHER_LIGHTNING_ON = WEATHER_LIGHTNING_CFG.enabled !== false;
+var WEATHER_LIGHTNING_GAIN = (typeof WEATHER_LIGHTNING_CFG.gain === 'number') ? Math.max(0, WEATHER_LIGHTNING_CFG.gain) : 1.2;
+var WEATHER_LIGHTNING_MIN_DELAY = (typeof WEATHER_LIGHTNING_CFG.minDelayS === 'number') ? Math.max(0.5, WEATHER_LIGHTNING_CFG.minDelayS) : 8;
+var WEATHER_LIGHTNING_MAX_DELAY = (typeof WEATHER_LIGHTNING_CFG.maxDelayS === 'number') ? Math.max(WEATHER_LIGHTNING_MIN_DELAY, WEATHER_LIGHTNING_CFG.maxDelayS) : 45;
+var WEATHER_LIGHTNING_DOUBLE = WEATHER_LIGHTNING_CFG.doubleFlash !== false;
+var lightningNextT = 0, lightningSeq = 0, lightningSeqT = 0, lightningFlash = 0;
+
+function updateLightning(now) {
+    if (!WEATHER_LIGHTNING_ON) {
+        lightningFlash = 0;
+        lightningSeq = 0;
+        return 0;
+    }
+    var wx = window.__currentWeather || {};
+    var code = Number(wx.code || 0);
+    var storm = code >= 95 || window.__currentWeatherName === 'stormy';
+    if (!storm) {
+        lightningFlash = 0;
+        lightningSeq = 0;
+        return 0;
+    }
+    if (now > lightningNextT) {
+        lightningSeq = 1 + (WEATHER_LIGHTNING_DOUBLE && Math.random() < 0.45 ? 1 : 0);
+        lightningSeqT = now;
+        lightningNextT = now + WEATHER_LIGHTNING_MIN_DELAY +
+            Math.random() * (WEATHER_LIGHTNING_MAX_DELAY - WEATHER_LIGHTNING_MIN_DELAY);
+    }
+    var flash = 0;
+    if (lightningSeq > 0) {
+        var dt = now - lightningSeqT;
+        var f1 = Math.exp(-dt * 12.0);
+        var f2 = lightningSeq > 1 ? Math.exp(-Math.max(0.0, dt - 0.12) * 10.0) : 0.0;
+        flash = Math.max(f1, f2 * 0.75);
+        if (dt > 1.2) lightningSeq = 0;
+    }
+    lightningFlash = flash;
+    return flash;
+}
+
 var weatherProg = null, weatherU = null;
 
 var WEATHER_VERT_SRC = [
@@ -6310,6 +6350,13 @@ window.clouds3dRender = function(target) {
         _moonI *= _exp;
         _amb *= _exp;
     }
+    var _lightning = updateLightning(now);
+    if (_lightning > 0.001) {
+        var _lightningGain = WEATHER_LIGHTNING_GAIN * _lightning;
+        _amb += _lightningGain * 0.85;
+        _beamL += _lightningGain * 0.35;
+        _beam = mixRgb(_beam, [0.82, 0.88, 1.0], Math.min(0.75, _lightning));
+    }
     var _terrainHazeColor = hazeColorDynamic(TERRAIN_HAZE_COLOR, _air, _amb, _star, _moonI);
     var _frontHazeColor = hazeColorDynamic(FRONT_HAZE_COLOR, _air, _amb, _star, _moonI);
     var _airHazeColor = hazeColorDynamic(AIR_HAZE_COLOR, _air, _amb, _star, _moonI);
@@ -7267,6 +7314,12 @@ window.clouds3dRender = function(target) {
     // ---- Weather overlay: rain/snow ------------------------------------
     if (WEATHER_FX_ON) {
         var _weather = weatherOverlayIntensities();
+        window.__weatherFxDbg = {
+            rain: +_weather[0].toFixed(2),
+            snow: +_weather[1].toFixed(2),
+            lightning: +lightningFlash.toFixed(2),
+            code: Number((window.__currentWeather || {}).code || 0)
+        };
         var _rainI = _weather[0];
         var _snowI = _weather[1];
         if (_rainI > 0.001 || _snowI > 0.001) {