fix(render): use view-dependent sky fog color

3 files changed, 55 insertions, 13 deletions

diff --git a/apps/fparkan-game/src/main.rs b/apps/fparkan-game/src/main.rs
index c94778d..49e40c0 100644
--- a/apps/fparkan-game/src/main.rs
+++ b/apps/fparkan-game/src/main.rs
@@ -3468,7 +3468,11 @@ impl DynamicEnvironment {
             target.active = source.active;
         }
         uniforms.lighting_floor = sky_frame.lighting_floor;
-        uniforms.fog_color = sky_frame.fog.color;
+        let fog_rgb = sky_frame
+            .screen_gradient(camera.native_sky_heading(), [0.0; 3])
+            .color
+            .rgba();
+        uniforms.fog_color = [fog_rgb[0], fog_rgb[1], fog_rgb[2]];
         uniforms.fog_start = sky_frame.fog.start.max(0.0);
         uniforms.fog_end = sky_frame.fog.end.max(uniforms.fog_start);
         uniforms.camera_position = camera.position;
@@ -7902,6 +7906,37 @@ mod tests {
     }
 
     #[test]
+    fn captured_native_camera_uses_view_dependent_sky_fog_color() {
+        use fparkan_fx::atmosphere::{PackedColor, SkySample, SKY_COLOR_COUNT};
+
+        // Compact camera fields from the native 1493.337-second AutoDemo capture.
+        let capture = parse_legacy_camera_capture(
+            br#"{"schema":"fparkan-legacy-camera-v1","render_input_usable":true,"parented_camera":true,"effective_world_matrix_space":"world","effective_world_matrix_words":[1052770830,1064129158,991881820,1141874407,3211610778,1052772554,3144770972,1145115441,3146624790,3127057462,1065352580,1087889619,0,0,0,1065353216],"selector0_words":[1063123992,3204380634,996787387,3130169600,1056894806,1063125889,990301923,3129510813,3146181515,3070164857,1065352633,1080608413,0,0,0,1065353216],"viewport":[0,0,1280,1024],"near_plane":5.0,"far_plane":700.0,"field_of_view_radians":1.3,"atmosphere_seconds":1493.337}"#,
+        )
+        .expect("valid native camera fixture");
+        let camera = capture.preview_camera_frame().expect("valid camera frame");
+
+        let mut colors = [PackedColor(0xFF00_0000); SKY_COLOR_COUNT];
+        colors[..4].copy_from_slice(&[
+            PackedColor(0xFF38_3864),
+            PackedColor(0xFF38_3864),
+            PackedColor(0xFF40_4064),
+            PackedColor(0xFF38_3864),
+        ]);
+        let sample = SkySample {
+            colors,
+            values: [0.0; 2],
+            packed: [PackedColor(0); 2],
+        };
+        let fog_color =
+            fparkan_fx::sky::screen_gradient_frame(&sample, camera.native_sky_heading(), [0.0; 3])
+                .color;
+
+        assert_eq!(capture.atmosphere_seconds, Some(1493.337));
+        assert_eq!(fog_color, PackedColor(0xFF3E_3E64));
+    }
+
+    #[test]
     fn sky_normals_keep_native_signed_byte_scale_without_renormalizing() {
         assert_eq!(sky_normal([-128, 127, -64]), [-1.0, 127.0 / 128.0, -0.5]);
     }
diff --git a/crates/fparkan-fx/src/sky.rs b/crates/fparkan-fx/src/sky.rs
index f41e920..26e68ab 100644
--- a/crates/fparkan-fx/src/sky.rs
+++ b/crates/fparkan-fx/src/sky.rs
@@ -957,12 +957,14 @@ impl fmt::Display for SkyUpdateError {
 
 impl std::error::Error for SkyUpdateError {}
 
-/// Fog values sent by the original `CSky` update.
+/// Distance and ambient-light values derived from an original `CSky` sample.
+///
+/// The renderer's `D3DRS_FOGCOLOR` is view-dependent: it is interpolated from
+/// `SkySample::colors[0..4]` using the native sky heading. It is not this
+/// sample-only frame value.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct FogFrame {
-    /// Normalized RGB fog color from `SkySample::packed[1]`.
-    pub color: [f32; 3],
-    /// Native global lighting floor from the same sampled RGB state.
+    /// Native global lighting floor from `SkySample::packed[1]`.
     ///
     /// `CShade` merges this vector with the material lighting accumulator by
     /// taking the per-channel maximum before the shader receives the result.
@@ -980,10 +982,8 @@ impl FogFrame {
         let start = finite_or_zero(sample.values[0]) * FOG_DISTANCE_SCALE;
         let end = finite_or_zero(sample.values[1]) * FOG_DISTANCE_SCALE;
         let rgba = sample.packed[1].rgba();
-        let color = [rgba[0], rgba[1], rgba[2]];
         Self {
-            color,
-            lighting_floor: color,
+            lighting_floor: [rgba[0], rgba[1], rgba[2]],
             start,
             end,
         }
@@ -1845,12 +1845,12 @@ mod tests {
     }
 
     #[test]
-    fn fog_uses_original_scale_and_packed_rgb() {
+    fn fog_distances_use_original_scale_and_floor_uses_packed_rgb() {
         let frame = fog_frame(&sample());
         assert_eq!(frame.start, 700.0);
         assert_eq!(frame.end, 1_400.0);
         assert_eq!(
-            frame.color,
+            frame.lighting_floor,
             [
                 0x11 as f32 / 255.0,
                 0x22 as f32 / 255.0,
@@ -1945,11 +1945,10 @@ mod tests {
 
         let mut atmosphere = atmosphere(true);
         atmosphere.sky.colors[12] = PackedColor(0xFF12_3456);
-        let (lighting_floor, fog_color, sprites_have_native_uv) = {
+        let (lighting_floor, sprites_have_native_uv) = {
             let frame = system.update(&atmosphere, 10.0).expect("sky update");
             (
                 frame.lighting_floor,
-                frame.fog.color,
                 frame
                     .sprites
                     .iter()
@@ -1969,7 +1968,8 @@ mod tests {
             positions
         );
         assert_eq!(system.mesh().vertices[0].color, PackedColor(0xFF12_3456));
-        assert_eq!(lighting_floor, fog_color);
+        let packed = atmosphere.sky.packed[1].rgba();
+        assert_eq!(lighting_floor, [packed[0], packed[1], packed[2]]);
         assert!(sprites_have_native_uv);
     }
 
diff --git a/docs/reference/environment-effects.md b/docs/reference/environment-effects.md
index 0435a6a..3267a2f 100644
--- a/docs/reference/environment-effects.md
+++ b/docs/reference/environment-effects.md
@@ -20,6 +20,13 @@ sky.wea
 backend разрешает архив и имя звука. Это позволяет одной и той же модели
 погоды работать в preview и в игровом цикле.
 
+Цвета неба, ambient lighting и fog renderer-а используют разные поля того же
+`sky.ske` sample. `SkySample::packed[1]` задаёт глобальный lighting floor;
+`CShade` объединяет его с material lighting по поканальному максимуму.
+`D3DRS_FOGCOLOR` (`0x22`) зависит от направления камеры и интерполируется из
+`SkySample::colors[0..4]` по native sky heading. Значения `sky.values[0..1]`
+продолжают задавать fog start/end, масштабируемые на 700.
+
 ## Входы и границы
 
 Для расписания используется такой вызов: