85 lines
2.1 KiB
C#
85 lines
2.1 KiB
C#
using Godot;
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using System;
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using Vim.Math3d;
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public class Orbit : IOrbit
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{
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#region IEllipse
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public double a => Ellipse.a;
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public double b => Ellipse.b;
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public double e => Ellipse.e;
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public DVector2[] Foci => Ellipse.Foci;
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#endregion
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public IEllipse Ellipse { get; set; }
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private double U => Kepler.U(_massive.Mass);
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private readonly IMassive _massive;
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private readonly ILocation _satellite;
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/// <summary>
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/// An orbit is treated as one stationary body at one focus of the orbit's ellipse.
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/// The satellite is treated as a massless point.
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/// </summary>
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/// <param name="massive">Mass of the object being orbited</param>
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/// <param name="satellite">The orbiting body</param>
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public Orbit(IMassive massive, ILocation satellite)
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{
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// semi-major axis is distance of satellite from origin
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var a = satellite.Position.Magnitude();
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// TODO: determine eccentricity better
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var e = 0.8f;
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this.Ellipse = new Ellipse(a, e);
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_massive = massive;
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_satellite = satellite;
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}
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public DVector3 GetPosition(float t)
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{
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var a = Ellipse.a;
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var e = Ellipse.e;
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Kepler.GetPeriod(a, U);
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// TODO: determine period from mass of orbiting bodies
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var P = 10f;
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var M = Kepler.GetMeanAnomaly(t, P);
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var E = Kepler.GetEccentricAnomaly(e, M) + Math.PI;
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var p = Kepler.GetEccentricPosition2D(e, a, t);
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return new DVector3(p.X, 0, p.Y);
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}
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public void Draw(ImmediateGeometry geo)
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{
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geo.Clear();
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geo.Begin(Mesh.PrimitiveType.LineLoop);
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DrawEllipse(geo);
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geo.End();
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}
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private void DrawEllipse(ImmediateGeometry geo)
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{
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geo.SetColor(new Color(1, 0, 0));
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int steps = 100;
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for (int i = 0; i < steps; i++)
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{
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float t = i / (float)steps;
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float a = t * Mathf.Tau;
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var v2 = Ellipse.Foci[0] + Ellipse.GetPosition(a);
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geo.AddVertex(new Godot.Vector3
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{
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x = (float)v2.X,
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z = (float)v2.Y
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});
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}
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}
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}
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