From d9af542d544c7eb6d8f3b93d9b89643e65cdfd4d Mon Sep 17 00:00:00 2001
From: yuni <hut@hut.pm>
Date: Sat, 8 Jun 2024 04:17:54 +0200
Subject: [PATCH] give objects orbiting jupiter an orbital velocity on startup

---
 src/cmd.rs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/cmd.rs b/src/cmd.rs
index f7f6a3e..17e37e7 100644
--- a/src/cmd.rs
+++ b/src/cmd.rs
@@ -617,6 +617,12 @@ fn spawn_entities(
     settings: Res<var::Settings>,
 ) {
     for state_wrapper in er_spawn.read() {
+        let jupiter_pos: DVec3 = if let Some(jupiter_pos) = id2pos.0.get(ID_JUPITER) {
+            *jupiter_pos
+        } else {
+            warn!("Could not determine Jupiter's position");
+            DVec3::ZERO
+        };
         let state = &state_wrapper.0;
         let mut rotation = state.rotation;
         if state.class == DefClass::Actor {
@@ -669,6 +675,12 @@ fn spawn_entities(
                 } * state.model_scale,
             );
             let orbits_jupiter = state.id != ID_JUPITER;
+            let velocity = if orbits_jupiter {
+                let coords = absolute_pos - jupiter_pos;
+                state.velocity + nature::orbital_velocity(coords, nature::JUPITER_MASS)
+            } else {
+                state.velocity
+            };
 
             // Spawn the actor
             let actor_entity;
@@ -719,7 +731,7 @@ fn spawn_entities(
                 // Physics Parameters
                 if state.has_physics {
                     actor.insert(RigidBody::Dynamic);
-                    actor.insert(LinearVelocity(state.velocity));
+                    actor.insert(LinearVelocity(velocity));
                     actor.insert(AngularVelocity(state.angular_momentum));
                     actor.insert(ColliderDensity(state.density));
                     if state.collider_is_mesh {