atmosphere: set dynamic fog density based on altitude

src/camera.rs

@@ -16,7 +16,7 @@ use crate::prelude::*;
 use bevy::core_pipeline::bloom::{BloomCompositeMode, BloomSettings};
 use bevy::core_pipeline::tonemapping::Tonemapping;
 use bevy::input::mouse::{MouseMotion, MouseWheel};
-use bevy::pbr::{CascadeShadowConfigBuilder, DirectionalLightShadowMap};
+use bevy::pbr::{CascadeShadowConfigBuilder, DirectionalLightShadowMap, VolumetricFogSettings, VolumetricLight};
 use bevy::prelude::*;
 use bevy::transform::TransformSystem;
 use bevy::window::PrimaryWindow;
@@ -33,6 +33,7 @@ impl Plugin for CameraPlugin {
         app.add_systems(Startup, setup_camera);
         app.add_systems(Update, handle_input.run_if(in_control).run_if(game_running));
         app.add_systems(Update, tweak_scene);
+        app.add_systems(Update, update_volumetric_fog);
         app.add_systems(
             Update,
             update_map_only_object_visibility
@@ -148,7 +149,8 @@ pub fn setup_camera(
             transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
             ..default()
         },
-        bevy::pbr::VolumetricFogSettings {
+        VolumetricFogSettings {
+            fog_color: Color::srgb(0.78, 0.76, 0.7),
             // This value is explicitly set to 0 since we have no environment map light
             ambient_intensity: 0.0,
             absorption: 0.1,
@@ -810,6 +812,22 @@ fn tweak_scene(
     for (light, mut directional_light) in lights.iter_mut() {
         // Shadows are needed for volumetric lights to work.
         directional_light.shadows_enabled = true;
-        commands.entity(light).insert(bevy::pbr::VolumetricLight);
+        commands.entity(light).insert(VolumetricLight);
+    }
+}
+
+pub fn update_volumetric_fog(settings: Res<Settings>, mut q_fog: Query<&mut VolumetricFogSettings>) {
+    let mut fog = if let Ok(x) = q_fog.get_single_mut() {
+        x
+    } else {
+        return;
+    };
+
+    if let Some(x) = settings.atmo_altitude {
+        // exponential regression with [(-1e5, 1.0), (0, 0.2), (20e5, 0.01)]
+        let density = 0.2 * 0.9999839f32.powf(x as f32);
+        fog.density = density;
+    } else {
+        fog.density = 0.0;
     }
 }

src/visual.rs

@@ -11,7 +11,7 @@
 // This module manages visual effects.
 
 use crate::prelude::*;
-use bevy::pbr::NotShadowReceiver;
+//use bevy::pbr::NotShadowReceiver;
 use bevy::prelude::*;
 use bevy_xpbd_3d::prelude::*;
 use std::time::Duration;
@@ -103,8 +103,8 @@ pub fn setup(
     mut commands: Commands,
     mut ew_effect: EventWriter<SpawnEffectEvent>,
     mut graphs: ResMut<Assets<AnimationGraph>>,
-    mut materials: ResMut<Assets<StandardMaterial>>,
+    //mut materials: ResMut<Assets<StandardMaterial>>,
-    mut meshes: ResMut<Assets<Mesh>>,
+    //mut meshes: ResMut<Assets<Mesh>>,
 ) {
     if !settings.dev_mode {
         ew_effect.send(SpawnEffectEvent {