sun: add configurable warm corona glow

config.js

@@ -650,9 +650,18 @@ window.CONFIG = {
     // scene lighting are NOT scaled with it.
     sun: {
         angularRadius: 0.0279,    // 6x the physical 0.00465 rad
-        brightness: 1.8           // sun disc/halo gain
+        brightness: 2.1,          // sun disc/glow gain
+        glow: {
+            enabled: true,
+            core: 1.15,           // bright inner corona
+            inner: 0.95,          // warm near halo
+            outer: 0.38,          // soft far halo
+            outerRadius: 11.0,    // outer halo radius in sun-disc radii
+            color: [1.00, 0.78, 0.36]
+        }
         // angularRadius: 0.0558, brightness: 1.0
         // angularRadius: 0.0140, brightness: 2.4
+        // glow: { core: 1.6, inner: 1.4, outer: 0.55, outerRadius: 14.0 }
     },
 
     // ------------------------------------------------------------------

vendor/clouds3d.js

@@ -142,7 +142,13 @@ var FRAG_SRC = [
     'uniform float uMoonFlipU;',
     'uniform float uMoonFlipV;',
     'uniform float uSunR;',       // sun disc angular radius (radians)
-    'uniform float uSunDiscGain;', // sun disc/halo brightness gain
+    'uniform float uSunDiscGain;', // sun disc/glow brightness gain
+    'uniform float uSunGlowOn;',
+    'uniform float uSunGlowCore;',
+    'uniform float uSunGlowInner;',
+    'uniform float uSunGlowOuter;',
+    'uniform float uSunGlowOuterRadius;',
+    'uniform vec3 uSunGlowColor;',
     // 3D hash and value noise
     'float hash3(vec3 p) {',
         'p = fract(p * vec3(0.1031, 0.1030, 0.0973));',
@@ -585,11 +591,18 @@ var FRAG_SRC = [
                 // physical by default) but the surface brightness stays
                 // exactly what it was: the halo profile is normalised to the
                 // disc radius, so the sun is bigger, not brighter.
-                'float angN = angS * (0.00465 / uSunR);',
+                'float angD = angS / max(0.0001, uSunR);',
-                'float discS = 1.0 - smoothstep(uSunR * 0.86, uSunR, angS);',
+                'float discS = 1.0 - smoothstep(0.78, 1.0, angD);',
-                'float haloS = exp(-angN * 55.0) * 0.30 + exp(-angN * 14.0) * 0.12;',
+                'float limb = 0.72 + 0.28 * (1.0 - clamp(angD, 0.0, 1.0));',
-                'vec3 sunCol = mix(uLight, vec3(1.0, 0.92, 0.72), 0.35);',
+                'float core = exp(-angD * 2.2) * uSunGlowCore;',
-                'col += sunCol * (discS * 1.15 + haloS) * uSunDiscGain * (1.0 - nightFactor * 0.85);',
+                'float inner = exp(-angD * 0.85) * uSunGlowInner;',
+                'float outer = exp(-angD * 0.22) * uSunGlowOuter;',
+                'float outerMask = 1.0 - smoothstep(uSunGlowOuterRadius * 0.45, uSunGlowOuterRadius, angD);',
+                'float glow = uSunGlowOn * (core + inner + outer * outerMask);',
+                'vec3 sunCol = mix(uLight, uSunGlowColor, 0.42);',
+                'vec3 glowCol = mix(uSunGlowColor, vec3(1.0, 0.96, 0.82), 0.32);',
+                'col += sunCol * discS * limb * 1.35 * uSunDiscGain * (1.0 - nightFactor * 0.85);',
+                'col += glowCol * glow * uSunDiscGain * (1.0 - nightFactor * 0.85);',
             '}',
             // ---- Moon disc: lunar map + geometric terminator --------------
             // The near side always faces the observer, so the map is sampled
@@ -1314,6 +1327,12 @@ function init(canvas) {
         uMoonFrac: uMoonFrac, uMoonEarth: uMoonEarth, uMoonLimb: uMoonLimb,
         uMoonBright: uMoonBright, uMoonHalo: uMoonHalo,
         uMoonFlipU: uMoonFlipU, uMoonFlipV: uMoonFlipV, uSunR: uSunR, uSunDiscGain: gl.getUniformLocation(prog, 'uSunDiscGain'),
+        uSunGlowOn: gl.getUniformLocation(prog, 'uSunGlowOn'),
+        uSunGlowCore: gl.getUniformLocation(prog, 'uSunGlowCore'),
+        uSunGlowInner: gl.getUniformLocation(prog, 'uSunGlowInner'),
+        uSunGlowOuter: gl.getUniformLocation(prog, 'uSunGlowOuter'),
+        uSunGlowOuterRadius: gl.getUniformLocation(prog, 'uSunGlowOuterRadius'),
+        uSunGlowColor: gl.getUniformLocation(prog, 'uSunGlowColor'),
         // terrain program
         terrain: {
             prog: terrainProg,
@@ -2788,6 +2807,13 @@ var SUN_CFG = (window.CONFIG && window.CONFIG.sun) || {};
 var SUN_ANG_R = (typeof SUN_CFG.angularRadius === 'number')
     ? Math.max(0.00465, SUN_CFG.angularRadius) : 0.00465 * 12;
 var SUN_DISC_GAIN = (typeof SUN_CFG.brightness === 'number') ? Math.max(0, SUN_CFG.brightness) : 1.0;
+var SUN_GLOW_CFG = SUN_CFG.glow || {};
+var SUN_GLOW_ON = SUN_GLOW_CFG.enabled !== false ? 1.0 : 0.0;
+var SUN_GLOW_CORE = (typeof SUN_GLOW_CFG.core === 'number') ? Math.max(0, Math.min(4, SUN_GLOW_CFG.core)) : 1.15;
+var SUN_GLOW_INNER = (typeof SUN_GLOW_CFG.inner === 'number') ? Math.max(0, Math.min(4, SUN_GLOW_CFG.inner)) : 0.95;
+var SUN_GLOW_OUTER = (typeof SUN_GLOW_CFG.outer === 'number') ? Math.max(0, Math.min(4, SUN_GLOW_CFG.outer)) : 0.38;
+var SUN_GLOW_OUTER_RADIUS = (typeof SUN_GLOW_CFG.outerRadius === 'number') ? Math.max(1, Math.min(40, SUN_GLOW_CFG.outerRadius)) : 11.0;
+var SUN_GLOW_COLOR = Array.isArray(SUN_GLOW_CFG.color) ? SUN_GLOW_CFG.color : [1.00, 0.78, 0.36];
 var MOON_TEX_SRC = (typeof window.__moonTex === 'string' && window.__moonTex)
     ? window.__moonTex
     : ((typeof MOON_CFG.texture === 'string' && MOON_CFG.texture) ? MOON_CFG.texture : 'vendor/moon.jpg');
@@ -7177,6 +7203,12 @@ window.clouds3dRender = function(target) {
     gl.uniform1f(s.uMoonFlipV, MOON_FLIP_V);
     gl.uniform1f(s.uSunR, SUN_ANG_R);
     gl.uniform1f(s.uSunDiscGain, SUN_DISC_GAIN);
+    gl.uniform1f(s.uSunGlowOn, SUN_GLOW_ON);
+    gl.uniform1f(s.uSunGlowCore, SUN_GLOW_CORE);
+    gl.uniform1f(s.uSunGlowInner, SUN_GLOW_INNER);
+    gl.uniform1f(s.uSunGlowOuter, SUN_GLOW_OUTER);
+    gl.uniform1f(s.uSunGlowOuterRadius, SUN_GLOW_OUTER_RADIUS);
+    gl.uniform3f(s.uSunGlowColor, SUN_GLOW_COLOR[0], SUN_GLOW_COLOR[1], SUN_GLOW_COLOR[2]);
     // texture path: RA alpha must land at world angle alpha + PI/2 - LST,
     // which with u = fract(0.5 + (H + uStarLon)/2PI) means uStarLon = LST - 3PI/2
     var _sidTex = starSidereal();