better orbit

Cargo.lock

@@ -3071,7 +3071,6 @@ dependencies = [
  "bevy",
  "bevy_rapier3d",
  "glam",
- "indexmap 2.0.0",
  "orbital",
 ]
 

Cargo.toml

@@ -19,5 +19,4 @@ bevy_rapier3d = { version = "0.22.0", features = [
     "debug-render-3d",
 ] }
 glam = { version = "0.24.1", features = ["debug-glam-assert"] }
-indexmap = "2.0.0"
 orbital = { git = "https://github.com/oli-obk/solar_sailors.git", rev = "2fabdd044f0f362595494dcad5102c50ae9572f7" }

src/forces.rs

@@ -1,12 +1,11 @@
-use std::any::TypeId;
+use std::{any::TypeId, collections::BTreeMap};
 
 use bevy::prelude::*;
 use bevy_rapier3d::prelude::ExternalForce;
-use indexmap::IndexMap;
 
 #[derive(Component, Default)]
 pub struct ExternalForceSet {
-    forces: IndexMap<TypeId, ExternalForce, ahash::RandomState>,
+    forces: BTreeMap<TypeId, ExternalForce>,
 }
 
 impl ExternalForceSet {

src/main.rs

@@ -9,6 +9,7 @@ use bevy::{
 };
 use bevy_rapier3d::prelude::*;
 use forces::ExternalForceSet;
+use glam::DVec2;
 
 use crate::forces::update_external_forces;
 
@@ -198,22 +199,19 @@ fn debug_spaceship_orbit(
     gizmos.ray(body_pos, rotated_pos, Color::FUCHSIA);
     gizmos.ray(
         body_pos,
-        rotated_vel.normalize_or_zero() * 120.0,
+        rotated_vel.normalize_or_zero() * 12000.0,
         Color::OLIVE,
     );
 
     let orbit = orbit::Orbit::from_pos_dir(
         body_gravity.mass.into(),
-        rotated_pos.x.into(),
-        rotated_pos.z.into(),
-        rotated_vel.x.into(),
-        rotated_vel.z.into(),
+        DVec2::new(rotated_pos.x.into(), rotated_pos.z.into()),
+        DVec2::new(rotated_vel.x.into(), rotated_vel.z.into()),
     );
     text.sections[1].value = format!("{:.2}", orbit.semi_major_axis);
     text.sections[3].value = format!("{:.2}", orbit.apoapsis());
     text.sections[5].value = format!("{:.2}", orbit.periapsis());
 
-
     gizmos.ray_gradient(ship_pos, velocity, Color::RED, Color::GREEN);
     gizmos.ray_gradient(ship_pos, translation, Color::BLUE, Color::GREEN);
 

src/orbit.rs

@@ -8,15 +8,14 @@ pub struct Orbit {
 
 pub const G: f64 = 6.6e-11;
 
-impl Orbit {
-    pub fn from_pos_dir(m: f64, x: f64, y: f64, vx: f64, vy: f64) -> Orbit {
-        let v = DVec2::new(vx, vy);
-        let v = v.length();
+fn cartesian_to_polar(pos: DVec2) -> (f64, f64) {
+    (pos.length(), f64::atan(pos.y / pos.x))
+}
 
-        let r_squared = x * x + y * y;
-        let r = r_squared.sqrt();
-        let theta = y.atan2(x);
-        let psi = vy.atan2(vx);
+impl Orbit {
+    pub fn from_pos_dir(m: f64, pos: DVec2, v: DVec2) -> Orbit {
+        let (r, theta) = cartesian_to_polar(pos);
+        let (v, psi) = cartesian_to_polar(v);
 
         // https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Celestial_Mechanics_(Tatum)/09%3A_The_Two_Body_Problem_in_Two_Dimensions/9.08%3A_Orbital_Elements_and_Velocity_Vector
 
@@ -48,17 +47,21 @@ impl Orbit {
 
 #[cfg(test)]
 mod tests {
+    use glam::DVec2;
+
     #[test]
     fn geostationary() {
-        let orbit = super::Orbit::from_pos_dir(5.972e24, 42000.0, 0.0, 0.0, 3074.0);
+        let orbit =
+            super::Orbit::from_pos_dir(5.972e24, DVec2::new(42000.0, 0.0), DVec2::new(0.0, 3074.0));
         assert!(
             (21000.0 - orbit.semi_major_axis) < 20.0,
             "{} == {}",
             21000.0,
             orbit.semi_major_axis
         );
+        // this is sus.
         assert!(
-            (1.0 - orbit.eccentricity) < 0.1,
+            (1.0 - orbit.eccentricity).abs() < 0.1,
             "{} == {}",
             1.0,
             orbit.eccentricity