new-horizons/NewHorizons/Components/Orbital/NHOrbitLine.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnityEngine;

namespace NewHorizons.Components.Orbital
{
    public class NHOrbitLine : OrbitLine
    {
		public Vector3 SemiMajorAxis { get; set; }
		public Vector3 SemiMinorAxis { get; set; }

		private Vector3 _upAxis;
		private float _fociDistance;
		private Vector3[] _verts;

		public override void InitializeLineRenderer()
		{
			base.GetComponent<LineRenderer>().positionCount = this._numVerts;
		}

		public override void OnValidate()
		{
			if (_numVerts < 0 || _numVerts > 4096)
			{
				_numVerts = Mathf.Clamp(_numVerts, 0, 4096);
			}
			if (base.GetComponent<LineRenderer>().positionCount != this._numVerts)
			{
				InitializeLineRenderer();
			}
		}

		public override void Start()
		{
			base.Start();

			var a = SemiMajorAxis.magnitude;
			var b = SemiMinorAxis.magnitude;

			_upAxis = Vector3.Cross(SemiMajorAxis.normalized, SemiMinorAxis.normalized);

			_fociDistance = Mathf.Sqrt(a * a - b * b);
			if (float.IsNaN(_fociDistance)) _fociDistance = 0f;

			_verts = new Vector3[this._numVerts];

			transform.localRotation = Quaternion.Euler(270, 90, 0);

			base.enabled = false;
		}

		public override void Update()
		{
			AstroObject primary = _astroObject?.GetPrimaryBody();
			
			// If it has nothing to orbit then why is this here
			if (primary == null)
			{
				base.enabled = false;
				return;
			}

			Vector3 origin = primary.transform.position + SemiMajorAxis.normalized * _fociDistance;

			float num = CalcProjectedAngleToCenter(origin, SemiMajorAxis, SemiMinorAxis, _astroObject.transform.position);
			
			for (int i = 0; i < _numVerts; i++)
			{
				float f = (float)i / (float)(_numVerts - 1) * 3.1415927f * 2f - (num + 3.1415927f);
				_verts[i] = SemiMajorAxis * Mathf.Cos(f) + SemiMinorAxis * Mathf.Sin(f);
			}
			_lineRenderer.SetPositions(_verts);

			transform.position = origin;
			transform.rotation = Quaternion.LookRotation(SemiMinorAxis, _upAxis);

			float num2 = DistanceToEllipticalOrbitLine(origin, SemiMajorAxis, SemiMinorAxis, _upAxis, Locator.GetActiveCamera().transform.position);
			float widthMultiplier = Mathf.Min(num2 * (_lineWidth / 1000f), _maxLineWidth);
			float num3 = _fade ? (1f - Mathf.Clamp01((num2 - _fadeStartDist) / (_fadeEndDist - _fadeStartDist))) : 1f;

			_lineRenderer.widthMultiplier = widthMultiplier;
			_lineRenderer.startColor = new Color(_color.r, _color.g, _color.b, num3 * num3);
		}

		private float CalcProjectedAngleToCenter(Vector3 foci, Vector3 semiMajorAxis, Vector3 semiMinorAxis, Vector3 point)
		{
			Vector3 lhs = point - foci;
			Vector3 vector = new Vector3(Vector3.Dot(lhs, semiMajorAxis.normalized), 0f, Vector3.Dot(lhs, semiMinorAxis.normalized));
			vector.x *= semiMinorAxis.magnitude / semiMajorAxis.magnitude;
			return Mathf.Atan2(vector.z, vector.x);
		}

		private float DistanceToEllipticalOrbitLine(Vector3 foci, Vector3 semiMajorAxis, Vector3 semiMinorAxis, Vector3 upAxis, Vector3 point)
		{
			float f = CalcProjectedAngleToCenter(foci, semiMajorAxis, semiMinorAxis, point);
			Vector3 b = foci + SemiMajorAxis * Mathf.Cos(f) + SemiMinorAxis * Mathf.Sin(f);
			return Vector3.Distance(point, b);
		}
	}
}