69 lines
1.6 KiB
C#
69 lines
1.6 KiB
C#
using Godot;
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using System;
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using Vim.Math3d;
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public struct Ellipse : IEllipse
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{
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public Ellipse(double a = 1, double e = 0)
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{
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SemiMajorAxis = a;
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Eccentricity = e;
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// TODO: this is an immutable struct, so initialise everything else
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// in the constructor to avoid recalculating properties whenever
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// they are accessed
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Apisides = new Apisides(a, e);
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b = Math.Sqrt(Apisides.max * Apisides.min);
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var d = Math.Sqrt(a * a - b * b);
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Foci = new DVector2[]
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{
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new DVector2(-d, 0),
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new DVector2(d, 0)
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};
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}
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/// <summary>
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/// Semi-major axis
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/// </summary>
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public double a => SemiMajorAxis;
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public double SemiMajorAxis { get; }
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/// <summary>
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/// Eccentricity
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/// </summary>
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public double e => Eccentricity;
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public double Eccentricity { get; }
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/// <summary>
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/// Semi-minor axis
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/// </summary>
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public double b { get; }
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/// <summary>
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/// Get a position on the auxiliary circle
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/// </summary>
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/// <param name="t">Angle in radians around the circle</param>
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/// <returns>2D position on the circle scaled by the semi-major axis</returns>
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public DVector2 GetAuxiliaryPosition2D(double t = 0) =>
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new DVector2(Math.Cos(t), Math.Sin(t)) * a;
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private Apisides Apisides { get; }
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public DVector2[] Foci { get; }
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private double GetFocusDistance() => Math.Sqrt(a * a - b * b);
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}
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public struct Apisides
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{
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public readonly double min;
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public readonly double max;
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public Apisides(double a, double e)
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{
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min = a * (1 - e);
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max = a * (1 + e);
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}
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} |