extract IOrbit and IOrbitExtensions

scripts/orbits/IOrbit.cs

@@ -0,0 +1,7 @@
+using Vim.Math3d;
+
+public interface IOrbit
+{
+    DVector3 GetPosition(double t);
+    IEllipse Ellipse { get; set; }
+}

scripts/orbits/IOrbitExtensions.cs

@@ -0,0 +1,29 @@
+using Godot;
+
+public static class IOrbitExtensions
+{
+    public static void Draw(this IOrbit orbit, ImmediateGeometry geo)
+    {
+        geo.Clear();
+        geo.Begin(Mesh.PrimitiveType.LineLoop);
+        geo.SetColor(new Color(1, 0, 0));
+
+        int steps = 100;
+        var ellipse = orbit.Ellipse;
+
+        for (int i = 0; i < steps; i++)
+        {
+            float t = i / (float)steps;
+            float a = t * Mathf.Tau;
+
+            var v2 = ellipse.Foci[0] + ellipse.GetPosition(a);
+
+            geo.AddVertex(new Godot.Vector3
+            {
+                x = (float)v2.X,
+                z = (float)v2.Y
+            });
+        }
+        geo.End();
+    }
+}