fix: improve cloud sunset tint and atmosphere color accuracy

Author: sandrwich

src/scene/atmosphere.ts

@@ -32,9 +32,9 @@ void main() {
   float brightness = mix(0.15, 1.0, sunBlend);
 
   // Atmosphere base color with sunset shift near terminator
-  vec3 dayColor = vec3(0.3, 0.6, 1.0);
-  vec3 sunsetColor = vec3(1.0, 0.5, 0.2);
-  float sunsetBlend = smoothstep(0.35, -0.15, NdotL);
+  vec3 dayColor = vec3(0.25, 0.58, 1.0);
+  vec3 sunsetColor = vec3(0.9, 0.45, 0.35);
+  float sunsetBlend = smoothstep(0.6, -0.25, NdotL);
   vec3 atmosColor = mix(dayColor, sunsetColor, sunsetBlend);
 
   // Forward-scatter glow: brighter when looking toward sun through the limb
@@ -56,7 +56,7 @@ export class Atmosphere {
 
   constructor() {
     const radius = (EARTH_RADIUS_KM + 80.0) / DRAW_SCALE;
-    const geometry = new THREE.SphereGeometry(radius, 64, 64);
+    const geometry = new THREE.SphereGeometry(radius, 128, 128);
 
     this.material = new THREE.ShaderMaterial({
       uniforms: {

src/shaders/cloud.frag.glsl

@@ -13,13 +13,13 @@ void main() {
     float intensity = dot(normal, sunDir);
     float alpha = smoothstep(-0.15, 0.05, intensity);
 
-    // Sunset tint on clouds: 2-stop gradient, multiplicative
-    float scatterMult = smoothstep(-0.15, 0.25, intensity) * smoothstep(0.25, -0.15, intensity);
-    vec3 sunsetDeep = vec3(0.85, 0.2, 0.08);
-    vec3 sunsetWarm = vec3(1.0, 0.55, 0.2);
-    float gradPos = smoothstep(-0.12, 0.12, intensity);
+    // Sunset tint on clouds: ISS-derived colors, normalized bell curve
+    float scatterMult = min(smoothstep(-0.3, 0.15, intensity) * smoothstep(0.15, -0.15, intensity) * 4.0, 1.0);
+    vec3 sunsetDeep = vec3(0.75, 0.08, 0.10);
+    vec3 sunsetWarm = vec3(1.0, 0.65, 0.55);
+    float gradPos = smoothstep(-0.1, 0.0, intensity);
     vec3 sunsetColor = mix(sunsetDeep, sunsetWarm, gradPos);
-    vec3 cloudColor = mix(texel.rgb, texel.rgb * sunsetColor * 1.5, scatterMult * 0.6);
+    vec3 cloudColor = mix(texel.rgb, sunsetColor, scatterMult * 0.7);
 
     gl_FragColor = vec4(cloudColor, texel.a * alpha);
 }

src/shaders/earth-daynight.frag.glsl

@@ -81,11 +81,11 @@ void main() {
     vec3 sunsetWarm = vec3(1.0, 0.55, 0.2);
     float gradPos = smoothstep(-0.12, 0.12, intensity);
     vec3 sunsetColor = mix(sunsetDeep, sunsetWarm, gradPos);
-    vec3 scatteredDay = mix(day.rgb * ao, day.rgb * ao * sunsetColor * 1.5, scatterMult * 0.5);
+    vec3 scatteredDay = mix(day.rgb * ao, day.rgb * ao * sunsetColor * 1.5, scatterMult * 0.15);
 
     // Surface haze: blue-to-sunset atmospheric haze near terminator
     vec3 hazeColor = mix(vec3(0.15, 0.35, 0.75), sunsetColor, scatterMult);
-    float surfaceHaze = pow(max(1.0 - abs(intensity), 0.0), 2.0) * smoothstep(-0.1, 0.2, intensity) * 0.35;
+    float surfaceHaze = pow(max(1.0 - abs(intensity), 0.0), 2.0) * smoothstep(-0.1, 0.2, intensity) * 0.1;
     scatteredDay = mix(scatteredDay, hazeColor, surfaceHaze);
 
     // Boost night emission for bloom (HDR values > 1.0)