Unity中 生成箭头（2D）

/*
/// 功能： 绘制箭头
/// 时间：
/// 版本：
*/

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

[AddComponentMenu("UI/Effects/Arrow")]
[RequireComponent(typeof(Image))]
[ExecuteInEditMode]
public class Arrow : BaseMeshEffect
{
    public enum DirectionType
    {
        Left,
        Right,
        Up,
        Down,
    }

    public DirectionType directionType;

    public float width = 1;
    public float height = 1;
    public float angle;
    public Color color;

    private Image image;

    protected override void Start()
    {
        image = this.GetComponent<Image>();
    }

    public override void ModifyMesh(VertexHelper vh)
    {
        vh.Clear();

        List<Vector3> vertexList = new List<Vector3>();
        Vector3 v0=Vector3.zero;
        Vector3 v1=Vector3.zero;
        Vector3 v2=Vector3.zero;
        Vector3 v3=Vector3.zero;
        Vector3 v4 = Vector3.zero;

        //有5个点"
        switch (directionType)
        {
            case DirectionType.Left:
                v1 = new Vector3(-width, 0);
                v2 = new Vector3(-width - height / Mathf.Tan(angle * Mathf.PI / 180), height / 2);
                v3 = new Vector3(-width, height);
                v4 = new Vector3(0, height);
                break;
            case DirectionType.Right:
                v1 = new Vector3(width, 0);
                v2 = new Vector3(width + height / Mathf.Tan(angle * Mathf.PI / 180), height / 2);
                v3 = new Vector3(width, height);
                v4 = new Vector3(0, height);
                break;
            case DirectionType.Up:
                v1 = new Vector3(width, 0);
                v2 = new Vector3(width,height);
                v3 = new Vector3(width/2, height+height/Mathf.Tan(angle*Mathf.PI/180));
                v4 = new Vector3(0, height);
                break;
            case DirectionType.Down:
                v1 = new Vector3(width, 0);
                v2 = new Vector3(width, -height);
                v3 = new Vector3(width / 2, -height - height / Mathf.Tan(angle * Mathf.PI / 180));
                v4 = new Vector3(0, -height);
                break;
            default:
                break;
        }

        vertexList.Add(v0, v1, v2, v3, v4);

        for (int i = 0; i < vertexList.Count; i++)
        {
            vh.AddVert(vertexList[i], color, Vector3.zero);
        }

        vh.AddTriangle(0, 1, 2);
        vh.AddTriangle(0, 1, 3);
        vh.AddTriangle(1, 2, 3);
        vh.AddTriangle(2, 3, 4);
        vh.AddTriangle(3, 4, 0);
        vh.AddTriangle(0, 1, 4);
    }

    private void Update()
    {
        image.SetVerticesDirty();
    }
}