moonwell-gfx: darker nights and deeper shadows, as WoW Forever's

The post pass takes from the dark and middle tones (eased off toward the bright, so a torch's
pool, a window or the moon keep theirs): post.shadow_depth at any hour, post.night_darkness
far further with the sun down, cooler and a little greyer. The lit air keeps 15% for the moon
(was 35%). The Forever preset sets both.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/moonwell-gfx/src/options.rs

@@ -217,6 +217,22 @@ const ITEMS: &[Item] = &[
         "Сила резкости",
         "Sharpen strength",
     ),
+    slider(
+        "post.shadow_depth",
+        0.0,
+        1.0,
+        0.05,
+        "Глубина теней",
+        "Shadow depth",
+    ),
+    slider(
+        "post.night_darkness",
+        0.0,
+        1.0,
+        0.05,
+        "Тёмные ночи",
+        "Dark nights",
+    ),
     switch("post.grading", "Цветокоррекция", "Colour grading"),
     slider("post.brightness", -0.5, 0.5, 0.01, "Яркость", "Brightness"),
     slider("post.contrast", 0.5, 2.0, 0.01, "Контраст", "Contrast"),

crates/moonwell-gfx/src/post.rs

@@ -188,7 +188,7 @@ fn publish(
     } else {
         0.0
     };
-    let night_share = if shadows.moon { 0.35 } else { 0.0 };
+    let night_share = if shadows.moon { 0.15 } else { 0.0 };
     // A low sun lights the air most: the glow and the rays are the dawn's and the dusk's, and the
     // noon keeps a third.
     let low_sun = 1.0 - 0.65 * smoothstep(0.25, 0.8, sun.y);
@@ -203,8 +203,20 @@ fn publish(
     } else {
         0.0
     };
+    // The dark: how much the dark and middle tones lose, deeper at night; and the night's cool,
+    // grey share.
+    let night = 1.0 - day;
+    let dark = (s.shadow_depth as f32 * 0.25 + s.night_darkness as f32 * 0.6 * night).min(0.7);
+    let night_tint = s.night_darkness as f32 * night;
     let post_on = s.enabled
-        && (s.grading || s.ao || s.sun_shafts || vol > 0.0 || sharpen > 0.0 || gi > 0.0 || fxaa);
+        && (s.grading
+            || s.ao
+            || s.sun_shafts
+            || vol > 0.0
+            || sharpen > 0.0
+            || gi > 0.0
+            || fxaa
+            || dark > 0.0);
     let next = (post_on || halo > 0.0).then(|| PostParams {
         grade: Vec4::new(
             s.brightness as f32,
@@ -212,7 +224,12 @@ fn publish(
             s.saturation as f32,
             s.vibrance as f32,
         ),
-        tone: Vec4::new(s.warmth as f32, on(post_on && s.grading), 0.0, 0.0),
+        tone: Vec4::new(
+            s.warmth as f32,
+            on(post_on && s.grading),
+            if post_on { dark } else { 0.0 },
+            if post_on { night_tint } else { 0.0 },
+        ),
         ao: Vec4::new(
             s.ao_strength as f32,
             s.ao_radius as f32,

crates/moonwell-gfx/src/settings.rs

@@ -120,6 +120,8 @@ impl GfxSettings {
         s.post.saturation = 1.15;
         s.post.vibrance = 0.2;
         s.post.secondary_light_strength = 1.2;
+        s.post.shadow_depth = 0.5;
+        s.post.night_darkness = 0.75;
         s.wind.enabled = true;
         s.water.enabled = true;
         s.lights.enabled = true;
@@ -353,6 +355,11 @@ pub struct PostSettings {
     pub secondary_light: bool,
     /// Its strength, 0..2.
     pub secondary_light_strength: f64,
+    /// Deeper shadows at any hour, 0..1: the dark and middle tones go down, the bright stay.
+    pub shadow_depth: f64,
+    /// Darker nights, 0..1: with the sun down the same curve goes much further, cooler and a
+    /// little greyer, so a torch, a lamp or a window stands out of the dark.
+    pub night_darkness: f64,
 }
 
 impl Default for PostSettings {
@@ -382,6 +389,8 @@ impl Default for PostSettings {
             antialias: true,
             secondary_light: true,
             secondary_light_strength: 0.8,
+            shadow_depth: 0.4,
+            night_darkness: 0.6,
         }
     }
 }
@@ -414,6 +423,8 @@ impl PostSettings {
             antialias: self.antialias,
             secondary_light: self.secondary_light,
             secondary_light_strength: self.secondary_light_strength.clamp(0.0, 2.0),
+            shadow_depth: self.shadow_depth.clamp(0.0, 1.0),
+            night_darkness: self.night_darkness.clamp(0.0, 1.0),
         }
     }
 }

crates/moonwell-gfx/src/shaders/post.wgsl

@@ -10,7 +10,7 @@
 struct Post {
     // brightness, contrast, saturation, vibrance
     grade: vec4<f32>,
-    // warmth, grade on, unused, unused
+    // warmth, grade on, what the dark tones lose (0 off), the night's tint
     tone: vec4<f32>,
     // strength, radius (yd), ao on, unused
     ao: vec4<f32>,
@@ -488,6 +488,25 @@ fn fxaa(uv: vec2<f32>, centre: vec3<f32>) -> vec3<f32> {
     return fxaa_at(out_uv);
 }
 
+// The dark: the dark and middle tones lose `tone.z` of their light and the bright (a torch's
+// pool, a window, the moon) keep theirs, eased between by the luma, as WoW Forever's dim places
+// and nights are; at night (`tone.w`) also cooler and a little greyer, as the eye sees in the dark.
+fn darkened(c: vec3<f32>) -> vec3<f32> {
+    let k = post.tone.z;
+    if (k <= 0.0) {
+        return c;
+    }
+    let l = dot(c, vec3<f32>(0.2126, 0.7152, 0.0722));
+    var x = c * mix(1.0 - k, 1.0, smoothstep(0.08, 0.75, l));
+    let n = post.tone.w;
+    if (n > 0.0) {
+        let grey = dot(x, vec3<f32>(0.2126, 0.7152, 0.0722));
+        x = mix(x, vec3<f32>(grey), 0.25 * n);
+        x = x * mix(vec3<f32>(1.0), vec3<f32>(0.86, 0.94, 1.12), 0.6 * n);
+    }
+    return x;
+}
+
 // The grade, in the gamma bytes the world pass writes.
 fn grade(c: vec3<f32>) -> vec3<f32> {
     var x = c + vec3<f32>(post.grade.x);
@@ -518,5 +537,6 @@ fn fragment(in: FullscreenVertexOutput) -> @location(0) vec4<f32> {
     if (post.tone.y > 0.5) {
         rgb = grade(rgb);
     }
+    rgb = darkened(rgb);
     return vec4<f32>(rgb, color.a);
 }