From 2d185a810b74d5bf08ea46b997734e881e4b3168 Mon Sep 17 00:00:00 2001
From: yuni <hut@hut.pm>
Date: Wed, 27 Nov 2024 02:33:02 +0100
Subject: [PATCH] WIP jupiter atmosphere

---
 src/actor.rs      | 68 ++++++++++++++++++++++++++++++++++++++++++-----
 src/cmd.rs        | 25 +++++++++++++++++
 src/data/defs.txt |  1 +
 src/nature.rs     |  2 ++
 4 files changed, 90 insertions(+), 6 deletions(-)

diff --git a/src/actor.rs b/src/actor.rs
index f213544..3297b10 100644
--- a/src/actor.rs
+++ b/src/actor.rs
@@ -58,12 +58,20 @@ impl Plugin for ActorPlugin {
 
         app.add_systems(
             PostUpdate,
-            handle_gforce
-                .run_if(game_running)
-                .run_if(alive)
-                .after(PhysicsSet::Sync)
-                .after(sync::position_to_transform)
-                .after(handle_wants_acceleration),
+            (
+                handle_gforce
+                    .run_if(game_running)
+                    .run_if(alive)
+                    .after(PhysicsSet::Sync)
+                    .after(sync::position_to_transform)
+                    .after(handle_wants_acceleration),
+                handle_atmosphere
+                    .run_if(game_running)
+                    .run_if(alive)
+                    .after(PhysicsSet::Sync)
+                    .after(sync::position_to_transform)
+                    .before(handle_gforce),
+            ),
         );
         app.add_systems(
             Update,
@@ -205,6 +213,13 @@ pub struct WantsMatchVelocityWith(pub String);
 pub struct Identifier(pub String);
 #[derive(Component)]
 pub struct OrbitsJupiter;
+#[derive(Component)]
+pub struct ExperiencesAtmosphere;
+#[derive(Component, Debug)]
+pub struct HasAtmosphere {
+    pub r_inner: f64,
+    pub r_outer: f64,
+}
 
 #[derive(Component)]
 pub struct LifeForm {
@@ -1109,3 +1124,44 @@ fn handle_gravity(
         v.0 += accel;
     }
 }
+
+fn handle_atmosphere(
+    time: Res<Time>,
+    q_atmosphere: Query<(&Position, Option<&LinearVelocity>, &HasAtmosphere)>,
+    mut q_actor: Query<
+        (&Position, &mut LinearVelocity),
+        (With<ExperiencesAtmosphere>, Without<HasAtmosphere>),
+    >,
+) {
+    let dt = time.delta_seconds() as f64;
+
+    for (pos, mut v) in &mut q_actor {
+        for (atmo_pos, atmo_v, atmo) in &q_atmosphere {
+            let distance = atmo_pos.distance(pos.0);
+            if distance < atmo.r_outer {
+                // height is between 0.0 (collides with planet) and 1.0 (outside of atmosphere)
+                let height = if distance < atmo.r_inner {
+                    0.0
+                } else {
+                    (distance - atmo.r_inner) / (atmo.r_outer - atmo.r_inner)
+                };
+
+                let dv = if let Some(atmo_v) = atmo_v {
+                    v.0 - atmo_v.0
+                } else {
+                    v.0
+                };
+                let friction = dv * (1.0 - height).powf(4.0) / 4.0;
+                v.0 -= friction;
+
+                if distance < atmo.r_inner {
+                    let outward = (pos.0 - atmo_pos.0).normalize();
+                    let buoyancy = outward * (atmo.r_inner - distance) * dt * 10.0;
+                    v.0 += buoyancy;
+                }
+
+                continue; // max. 1 atmosphere
+            }
+        }
+    }
+}
diff --git a/src/cmd.rs b/src/cmd.rs
index 91658ba..99384a6 100644
--- a/src/cmd.rs
+++ b/src/cmd.rs
@@ -103,6 +103,7 @@ struct ParserState {
     is_tidally_locked: bool,
     is_mirror: bool,
     is_orbitring: bool,
+    atmosphere: Option<String>,
     orbit_distance: Option<f64>,
     orbit_object_id: Option<String>,
     orbit_phase: Option<f64>,
@@ -168,6 +169,7 @@ impl Default for ParserState {
             is_tidally_locked: false,
             is_mirror: false,
             is_orbitring: false,
+            atmosphere: None,
             orbit_distance: None,
             orbit_object_id: None,
             orbit_phase: None,
@@ -647,6 +649,9 @@ pub fn load_defs(mut ew_spawn: EventWriter<SpawnEvent>) {
             ["collider", "handcrafted"] => {
                 state.collider_is_one_mesh_of_scene = true;
             }
+            ["atmosphere", atmosphere_id] => {
+                state.atmosphere = Some(atmosphere_id.to_string());
+            }
             ["player", "yes"] => {
                 state.is_player = true;
                 state.is_alive = true;
@@ -1465,6 +1470,8 @@ fn spawn_entities(
             });
         }
         if state.is_player || state.is_vehicle {
+            actor.insert(actor::ExperiencesAtmosphere);
+
             // used to apply mouse movement to actor rotation
             actor.insert(ExternalTorque::ZERO.with_persistence(false));
         }
@@ -1582,6 +1589,24 @@ fn spawn_entities(
                 ));
             });
         }
+        if state.atmosphere.is_some() {
+            let atmosphere_id = state.atmosphere.clone().unwrap();
+            let component = match atmosphere_id.as_str() {
+                "jupiter" => {
+                    Some(actor::HasAtmosphere {
+                        r_inner: scale.x as f64 * 1.01,
+                        r_outer: scale.x as f64 * 1.01 + nature::JUPITER_ATMO_HEIGHT,
+                    })
+                }
+                _ => {
+                    error!("Unknown atmosphere id `{atmosphere_id}`");
+                    None
+                }
+            };
+            if let Some(component) = component {
+                actor.insert(component);
+            }
+        }
         actor_entity = actor.id();
 
         for ar_asset_name in &state.ar_models {
diff --git a/src/data/defs.txt b/src/data/defs.txt
index 3fe3cb4..885ca01 100644
--- a/src/data/defs.txt
+++ b/src/data/defs.txt
@@ -85,6 +85,7 @@ actor 0 0 0
         sphere yes
         ring yes
         aurora yes
+        atmosphere jupiter
         physics off
         rotationy 3.13
         rotationz 135
diff --git a/src/nature.rs b/src/nature.rs
index 7c024fd..28ba663 100644
--- a/src/nature.rs
+++ b/src/nature.rs
@@ -34,6 +34,8 @@ pub const SOL_MASS: f64 = 1.9885e30;
 pub const JUPITER_MASS: f64 = 1.8982e27;
 pub const EARTH_MASS: f64 = 5.972168e24;
 
+pub const JUPITER_ATMO_HEIGHT: f64 = 1_000_000.0;
+
 // Arbitrary offset to time epoch, to generate more interesting orbital arrangements:
 pub const ORBIT_TIME_OFFSET: f64 = 614533234154.0;