From fe11d6d5bcb9a3b02ebf9677e2e68e57cd5a6f4e Mon Sep 17 00:00:00 2001
From: Hugo Peixoto <hugo.peixoto@gmail.com>
Date: Thu, 12 May 2022 00:56:47 +0100
Subject: [PATCH] Split sky shader's twilight into dawn and dusk

Instead of having the same color profiles for the sky's color, light,
and halo, we now have the ability to define different values for dawn
and dusk.

The dusk values were unchanged and the dawn values are similar, but with
less red. These should probably be tweaked a bit more.
---
 assets/voxygen/shaders/include/sky.glsl | 31 +++++++++++++++++++++----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/assets/voxygen/shaders/include/sky.glsl b/assets/voxygen/shaders/include/sky.glsl
index 585a5ef5f4..9c2b9bd0ce 100644
--- a/assets/voxygen/shaders/include/sky.glsl
+++ b/assets/voxygen/shaders/include/sky.glsl
@@ -18,6 +18,12 @@ struct DirectionalLight {
 
 const float PI = 3.141592;
 
+const vec3 SKY_DAWN_TOP = vec3(0.10, 0.1, 0.10);
+const vec3 SKY_DAWN_MID = vec3(1.2, 0.3, 0.2);
+const vec3 SKY_DAWN_BOT = vec3(0.0, 0.1, 0.23);
+const vec3 DAWN_LIGHT   = vec3(5.0, 2.0, 1.15);
+const vec3 SUN_HALO_DAWN = vec3(8.2, 3.0, 2.1);
+
 const vec3 SKY_DAY_TOP = vec3(0.1, 0.5, 0.9);
 const vec3 SKY_DAY_MID = vec3(0.02, 0.28, 0.8);
 const vec3 SKY_DAY_BOT = vec3(0.1, 0.2, 0.3);
@@ -143,9 +149,11 @@ float get_moon_brightness(/*vec3 moon_dir*/) {
 }
 
 vec3 get_sun_color(/*vec3 sun_dir*/) {
+    vec3 light = (sun_dir.x > 0) ? DUSK_LIGHT : DAWN_LIGHT;
+
     return mix(
         mix(
-            DUSK_LIGHT * magnetosphere_tint,
+            light * magnetosphere_tint,
             NIGHT_LIGHT,
             max(sun_dir.z, 0)
         ),
@@ -450,9 +458,22 @@ vec3 get_sky_light(vec3 dir, float time_of_day, bool with_stars) {
         star = is_star_at(star_dir);
     }
 
+    vec3 sky_twilight_top = vec3(0.0, 0.0, 0.0);
+    vec3 sky_twilight_mid = vec3(0.0, 0.0, 0.0);
+    vec3 sky_twilight_bot = vec3(0.0, 0.0, 0.0);
+    if (sun_dir.x > 0) {
+      sky_twilight_top = SKY_DUSK_TOP;
+      sky_twilight_mid = SKY_DUSK_MID;
+      sky_twilight_bot = SKY_DUSK_BOT;
+    } else {
+      sky_twilight_top = SKY_DAWN_TOP;
+      sky_twilight_mid = SKY_DAWN_MID;
+      sky_twilight_bot = SKY_DAWN_BOT;
+    }
+
     vec3 sky_top = mix(
         mix(
-            SKY_DUSK_TOP * magnetosphere_tint,
+            sky_twilight_top * magnetosphere_tint,
             SKY_NIGHT_TOP,
             pow(max(sun_dir.z, 0.0), 0.2)
         ) + star,
@@ -462,7 +483,7 @@ vec3 get_sky_light(vec3 dir, float time_of_day, bool with_stars) {
 
     vec3 sky_mid = mix(
         mix(
-            SKY_DUSK_MID * magnetosphere_tint,
+            sky_twilight_mid * magnetosphere_tint,
             SKY_NIGHT_MID,
             pow(max(sun_dir.z, 0.0), 0.1)
         ),
@@ -472,7 +493,7 @@ vec3 get_sky_light(vec3 dir, float time_of_day, bool with_stars) {
 
     vec3 sky_bot = mix(
         mix(
-            SKY_DUSK_BOT * magnetosphere_tint,
+            sky_twilight_bot * magnetosphere_tint,
             SKY_NIGHT_BOT,
             pow(max(sun_dir.z, 0.0), 0.2)
         ),
@@ -507,7 +528,7 @@ vec3 get_sky_color(vec3 dir, float time_of_day, vec3 origin, vec3 f_pos, float q
     const vec3 SUN_SURF_COLOR = vec3(1.5, 0.9, 0.35) * 50.0;
 
     vec3 sun_halo_color = mix(
-        SUN_HALO_DUSK * magnetosphere_tint,
+        (sun_dir.x > 0 ? SUN_HALO_DUSK : SUN_HALO_DAWN)* magnetosphere_tint,
         SUN_HALO_DAY,
         pow(max(-sun_dir.z, 0.0), 0.5)
     );