OrbitSystem -> Barycenter

scenes/orbits/Barycenter.tscn

@@ -0,0 +1,18 @@
+[gd_scene load_steps=3 format=2]
+
+[ext_resource path="res://scripts/orbits/Barycenter.cs" type="Script" id=1]
+[ext_resource path="res://scenes/orbits/Planet.tscn" type="PackedScene" id=2]
+
+[node name="Barycenter" type="Spatial"]
+script = ExtResource( 1 )
+SemiMajorAxis = 7.0
+Eccentricity = 0.752
+_pointMassPaths = [ NodePath("Planet A"), NodePath("Planet B") ]
+_speed = 1.0
+
+[node name="Planet A" parent="." instance=ExtResource( 2 )]
+transform = Transform( 0.999977, 0.00603502, 0.00319089, -0.00604282, 0.999979, 0.0024369, -0.00317609, -0.00245615, 0.999992, -2.55711, 0, -4.25519 )
+
+[node name="Planet B" parent="." instance=ExtResource( 2 )]
+transform = Transform( 0.5, 0, 0, 0, 0.5, 0, 0, 0, 0.5, -11.9998, 0, 1.25565 )
+Mass = 0.125

scenes/orbits/OrbitSystem.tscn

@@ -1,22 +0,0 @@
-[gd_scene load_steps=3 format=2]
-
-[ext_resource path="res://scripts/orbits/OrbitSystem.cs" type="Script" id=1]
-[ext_resource path="res://scenes/orbits/Planet.tscn" type="PackedScene" id=2]
-
-[node name="Orbit System" type="Spatial"]
-script = ExtResource( 1 )
-SemiMajorAxis = 6.881
-Eccentricity = 0.399
-Period = 10.0
-_a = NodePath("Planet A")
-_b = NodePath("Planet B")
-_barycenter = NodePath("Barycenter")
-
-[node name="Barycenter" type="Spatial" parent="."]
-
-[node name="Planet A" parent="." instance=ExtResource( 2 )]
-transform = Transform( 0.999977, 0.00603502, 0.00319089, -0.00604282, 0.999979, 0.0024369, -0.00317609, -0.00245615, 0.999992, 0, 0, 0 )
-
-[node name="Planet B" parent="." instance=ExtResource( 2 )]
-transform = Transform( 0.5, 0, 0, 0, 0.5, 0, 0, 0, 0.5, -8.44634, 0, -3.53339 )
-Mass = 0.125

scripts/orbits/Barycenter.cs

@@ -1,13 +1,13 @@
 using Godot;
 using System;
+using System.Collections.Generic;
 using Vim.Math3d;
 
 [Tool]
-public class OrbitSystem : Node, IMassive, ILocation
+public class Barycenter : Node, IPointMass
 {
-    [Export] private NodePath _a;
+    [Export]
-    [Export] private NodePath _b;
+    private NodePath[] _pointMassPaths;
-    [Export] private NodePath _barycenter;
 
     private double _semiMajorAxis;
     [Export]
@@ -40,79 +40,19 @@ public class OrbitSystem : Node, IMassive, ILocation
         }
     }
 
-    #region Point Masses
+    public double Mass
-    private IPointMass Primary
     {
         get
         {
-            if (_pointMasses[0] == null)
+            double mass = 0;
+            foreach (var orbiter in Orbiters)
             {
-                InitPointMasses();
+                mass += orbiter.PointMass.Mass;
             }
-            return _pointMasses[0];
+            return mass;
-        }
-    }
-    private IPointMass Secondary
-    {
-        get
-        {
-            if (_pointMasses[1] == null)
-            {
-                InitPointMasses();
-            }
-            return _pointMasses[1];
-        }
-    }
-    private readonly IPointMass[] _pointMasses = new IPointMass[2];
-    private void InitPointMasses()
-    {
-        var a = GetNode<IPointMass>(_a);
-        var b = GetNode<IPointMass>(_b);
-
-        if (a.Mass > b.Mass)
-        {
-            _pointMasses[0] = a;
-            _pointMasses[1] = b;
-        }
-        else
-        {
-            _pointMasses[0] = b;
-            _pointMasses[1] = a;
-        }
-    }
-    #endregion
-
-    public float Mass => Primary.Mass + Secondary.Mass;
-    public DVector3 Position
-    {
-        get => Barycenter;
-        set => Barycenter = value;
-    }
-
-    public DVector3 Barycenter
-    {
-        get
-        {
-            var p0 = Primary.Position;
-            var p1 = Secondary.Position;
-            return p0.Lerp(p1, .5f);
-        }
-        // TODO - make setting the berycenter do something sensible?
-        set => _ = value;
-    }
-
-    private Orbit _orbit = null;
-    private Orbit Orbit
-    {
-        get
-        {
-            if (_orbit == null)
-            {
-                _orbit = new Orbit();
-            }
-            return _orbit;
         }
     }
+    public DVector3 Position { get; set; }
 
     private ImmediateGeometry _orbitGeometry = null;
     public ImmediateGeometry OrbitGeometry
@@ -132,6 +72,50 @@ public class OrbitSystem : Node, IMassive, ILocation
         }
     }
 
+    private struct Orbiter
+    {
+        public IPointMass PointMass { get; set; }
+        public IOrbit Orbit { get; set; }
+    }
+    private Orbiter[] _orbiters = null;
+    private Orbiter[] Orbiters
+    {
+        get
+        {
+            if (_orbiters == null)
+            {
+                var length = _pointMassPaths.Length;
+                _orbiters = new Orbiter[length];
+                for (int i = 0; i < length; i++)
+                {
+                    var pointMass = GetNode<IPointMass>(_pointMassPaths[i]);
+                    var orbit = new Orbit(this, pointMass);
+
+                    var orbiter = new Orbiter
+                    {
+                        PointMass = pointMass,
+                        Orbit = orbit
+                    };
+                    _orbiters[i] = orbiter;
+                }
+            }
+            return _orbiters;
+        }
+    }
+
+    private IOrbit[] _orbits;
+    private IOrbit[] Orbits
+    {
+        get
+        {
+            if (_orbits == null)
+            {
+
+            }
+            return _orbits;
+        }
+    }
+
     private float _time = 0;
 
     [Export]
@@ -145,9 +129,15 @@ public class OrbitSystem : Node, IMassive, ILocation
 
     private void InvalidateGeometry()
     {
-        Orbit.Ellipse = new Ellipse(SemiMajorAxis, Eccentricity);
+        for (int i = 0; i < Orbiters.Length; i++)
-        Orbit.Draw(OrbitGeometry);
+        {
+            var orbiter = Orbiters[i];
+            var orbit = orbiter.Orbit;
+            orbit.Ellipse = new Ellipse(SemiMajorAxis, Eccentricity);
+            orbit.Draw(OrbitGeometry);
 
-        Secondary.Position = Orbit.GetPosition(_time);
+            var t = _time + i * Math.PI;
+            orbiter.PointMass.Position = orbit.GetPosition(t);
+        }
     }
 }