atmosphere: broaden bright sky band above horizon

vendor/clouds3d.js

@@ -383,7 +383,7 @@ var FRAG_SRC = [
             // skyT floor at 0.5: at and below the horizon the sky keeps
             // the exact horizon colour - the same value the terrain's
             // distance fog saturates to, so no seam at the silhouette.
-            'float skyT = clamp(rd.y * 0.55 + 0.5, 0.5, 1.0);',
+            'float skyT = clamp(rd.y * 0.45 + 0.5, 0.5, 1.0);',
             'vec3 col = mix(uBg, uSky, skyT);',
             'if (uPhysicalSkyOn > 0.5) {',
                 'float cosT = dot(rd, uSunDir);',
@@ -492,10 +492,10 @@ var FRAG_SRC = [
             // the ground has a different colour than the sky next to it
             // and reads as a hard edge.
             'if (uPhysical > 0.5) {',
-                'float lowBand = 1.0 - smoothstep(-0.08, 0.35, rd.y);',
+                'float lowBand = 1.0 - smoothstep(-0.10, 0.55, rd.y);',
                 'float cosTA = dot(rd, uSunDir);',
                 'float phaseA = 0.5 + 0.5 * cosTA * cosTA;',
-                'col = mix(col, uAirColor * phaseA * 1.25, lowBand * 0.92);',
+                'col = mix(col, uAirColor * phaseA * 1.45, lowBand * 0.95);',
             '}',
             'gl_FragColor = vec4(col, 1.0);',
             'return;',