From 727d8d2493f8e720b7fe9cac2b444a7d51134eb2 Mon Sep 17 00:00:00 2001
From: yuni <hut@hut.pm>
Date: Fri, 29 Nov 2024 19:19:58 +0100
Subject: [PATCH] atmosphere: add volumetric fog (WIP)

---
 src/camera.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/camera.rs b/src/camera.rs
index 66e6a81..2df37d2 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -32,6 +32,7 @@ impl Plugin for CameraPlugin {
     fn build(&self, app: &mut App) {
         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_map_only_object_visibility
@@ -147,6 +148,14 @@ pub fn setup_camera(
             transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
             ..default()
         },
+        bevy::pbr::VolumetricFogSettings {
+            // This value is explicitly set to 0 since we have no environment map light
+            ambient_intensity: 0.0,
+            absorption: 0.1,
+            density: 0.01,
+            step_count: 16,
+            ..default()
+        },
         bevy::core_pipeline::fxaa::Fxaa {
             edge_threshold: bevy::core_pipeline::fxaa::Sensitivity::Extreme,
             ..default()
@@ -793,3 +802,14 @@ pub fn position_to_transform(
         transform.rotation = rot.as_quat();
     }
 }
+
+fn tweak_scene(
+    mut commands: Commands,
+    mut lights: Query<(Entity, &mut DirectionalLight), Changed<DirectionalLight>>,
+) {
+    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);
+    }
+}