sun: halve disc size and add brightness gain

config.js

@@ -649,7 +649,10 @@ window.CONFIG = {
     // drawn larger so it reads as a disc; the surface brightness and the
     // scene lighting are NOT scaled with it.
     sun: {
-        angularRadius: 0.0558     // 12x the physical 0.00465 rad
+        angularRadius: 0.0279,    // 6x the physical 0.00465 rad
+        brightness: 1.8           // sun disc/halo gain
+        // angularRadius: 0.0558, brightness: 1.0
+        // angularRadius: 0.0140, brightness: 2.4
     },
 
     // ------------------------------------------------------------------

vendor/clouds3d.js

@@ -142,6 +142,7 @@ 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
     // 3D hash and value noise
     'float hash3(vec3 p) {',
         'p = fract(p * vec3(0.1031, 0.1030, 0.0973));',
@@ -588,7 +589,7 @@ var FRAG_SRC = [
                 'float discS = 1.0 - smoothstep(uSunR * 0.86, uSunR, angS);',
                 'float haloS = exp(-angN * 55.0) * 0.30 + exp(-angN * 14.0) * 0.12;',
                 'vec3 sunCol = mix(uLight, vec3(1.0, 0.92, 0.72), 0.35);',
-                'col += sunCol * (discS * 1.15 + haloS) * (1.0 - nightFactor * 0.85);',
+                'col += sunCol * (discS * 1.15 + haloS) * uSunDiscGain * (1.0 - nightFactor * 0.85);',
             '}',
             // ---- Moon disc: lunar map + geometric terminator --------------
             // The near side always faces the observer, so the map is sampled
@@ -1312,7 +1313,7 @@ function init(canvas) {
         uMoonTex: uMoonTex, uMoonTexOn: uMoonTexOn, uMoonR: uMoonR,
         uMoonFrac: uMoonFrac, uMoonEarth: uMoonEarth, uMoonLimb: uMoonLimb,
         uMoonBright: uMoonBright, uMoonHalo: uMoonHalo,
-        uMoonFlipU: uMoonFlipU, uMoonFlipV: uMoonFlipV, uSunR: uSunR,
+        uMoonFlipU: uMoonFlipU, uMoonFlipV: uMoonFlipV, uSunR: uSunR, uSunDiscGain: gl.getUniformLocation(prog, 'uSunDiscGain'),
         // terrain program
         terrain: {
             prog: terrainProg,
@@ -2786,6 +2787,7 @@ var MOON_FLIP_V = MOON_CFG.flipV ? 1 : 0;
 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 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');
@@ -7174,6 +7176,7 @@ window.clouds3dRender = function(target) {
     gl.uniform1f(s.uMoonFlipU, MOON_FLIP_U);
     gl.uniform1f(s.uMoonFlipV, MOON_FLIP_V);
     gl.uniform1f(s.uSunR, SUN_ANG_R);
+    gl.uniform1f(s.uSunDiscGain, SUN_DISC_GAIN);
     // 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();