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

public class LineDrawer : MonoBehaviour
{
    List<Vector3> lines;

    static Material lineMaterial;
    static void CreateLineMaterial()
    {
        if (!lineMaterial)
        {
            Shader shader = Shader.Find("Hidden/Internal-Colored");
            lineMaterial = new Material(shader);
            lineMaterial.hideFlags = HideFlags.HideAndDontSave;
            lineMaterial.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
            lineMaterial.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
            lineMaterial.SetInt("_Cull", (int)UnityEngine.Rendering.CullMode.Off);
            lineMaterial.SetInt("_ZWrite", 0);
            lineMaterial.color = Color.yellow;
        }
    }
    // Start is called before the first frame update
    void Start()
    {
        lines = new List<Vector3>();
        lines.Add(new Vector3(1, 1, 1));
        lines.Add(new Vector3(1, -1, 1));
        lines.Add(new Vector3(-1, 1, 1));
        lines.Add(new Vector3(-1, -1, 1));
        lines.Add(new Vector3(1, 1, -1));
        lines.Add(new Vector3(1, -1, -1));
        lines.Add(new Vector3(-1, 1, -1));
        lines.Add(new Vector3(-1, -1, -1));
    }

    private void OnPostRender()
    {
        CreateLineMaterial();
        lineMaterial.SetPass(0);
        for (int i = 0; i < lines.Count - 1; i++)
        {
            GL.Begin(GL.LINES);
            GL.Vertex(lines[i]);
            GL.Vertex(lines[i + 1]);
            GL.End();
        }
    }
}