Arrow.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Arrow : MonoBehaviour {

    [SerializeField]
    Rigidbody r;

    [SerializeField]
    Transform left;

    [SerializeField]
    Transform right;

    [SerializeField]
    Transform left2;

    [SerializeField]
    Transform obj;

    float speed = -1f;


    void Update(){
        //CirclarMotion ();
        ElliptiicalMotionBy2Points();
    }

    //2点間を直径とする正円運動
    void CirclarMotionByDiameter(){
        //cosθ = a(底辺)/c(斜辺)
        //a = c*cosθ
        //a = radius*cosθ

        //sinθ = b(高さ)/c(斜辺)
        //b = c * sinθ;
        //b = radius * sinθ

        //円の中心
        Vector3 a = left.position;
        Vector3 b = right.position;
        Vector3 center = new Vector3 ((a.x + b.x) / 2, (a.y + b.y) / 2, (a.z + b.z) / 2);

        //円の半径
        float radius = Vector3.Distance (a, center);
        float c = Time.time * speed;
        float x = radius * Mathf.Cos (c);
        float y = radius * Mathf.Sin (c);
        obj.position = new Vector3 (x, y, obj.position.z) + center;
    }

    //2点を通る楕円運動
    void ElliptiicalMotionBy2Points(){
        Vector3 a = left2.position;
        Vector3 b = right.position;
        Vector3 center = new Vector3 (a.x , b.y, (a.z + b.z) / 2);

        //円の半径
        float radiusX = Vector3.Distance (b, center);
        float radiusY = Vector3.Distance (a, center);

        float c = Time.time * speed;
        float x = radiusX * Mathf.Cos (c);
        float y = radiusY * Mathf.Sin (c);

        obj.position = new Vector3 (x, y, obj.position.z) + center;

    }

    //3点を通る正円運動
    void CirclarMotionBy2Points(){
        //中心(a,b)の円の半径を求める式は
        //(x-a)^2 + (y - b)^2 = r^2
        //これを一般形にすると、(aとbになんでもいいから入れるとわかる）
        //x^2 + y^2 +lx + my + n = 0
        //となるので、まず3点を定義する
        //とやろうと思ったけどプログラムで連立方程式なんてできるの。。。？

        //なので、
        //中心をO(x,y)とすると、OA=OB=OCであるので、

        Vector3 a = left2.position;
        Vector3 b = right.position;
        Vector3 c = left.position;




    }
}