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

public class FakeCamFrustum : MonoBehaviour {

    public float farDistance;
    public float fov;
    public float viewRatio;
    public Material frustumMat;

    float farHeight,farWidth;
    Vector3 farCenter, farTopLeft, farTopRight, farBotLeft, farBotRight;

    GameObject[] Triangles;
    
    void Start () {

        farHeight = 2.0f * farDistance * Mathf.Tan(fov * 0.5f * Mathf.Deg2Rad);
        farWidth = farHeight * viewRatio;

        farCenter = transform.position - transform.forward * farDistance;

        farTopLeft = farCenter + transform.up * (farHeight * 0.5f) - transform.right * (farWidth * 0.5f);
        farTopRight = farCenter + transform.up * (farHeight * 0.5f) + transform.right * (farWidth * 0.5f);
        farBotLeft = farCenter - transform.up * (farHeight * 0.5f) - transform.right * (farWidth * 0.5f);
        farBotRight = farCenter - transform.up * (farHeight * 0.5f) + transform.right * (farWidth * 0.5f);

        Triangles = new GameObject[4];

        for (int i = 0; i < 4; i++)
        {
            GameObject child = new GameObject();
            MeshFilter mf = child.AddComponent<MeshFilter>();
            child.transform.parent = transform;
            Triangles[i] = child;

            Vector3[] vertices = new Vector3[]
            {
                Vector3.zero,
                Vector3.zero,
                Vector3.zero
            };
            Vector3[] normals = new Vector3[]
            {
                Vector3.zero,
                Vector3.zero,
                Vector3.zero
            };
            int[] triangles = new int[]
            {
             2,1,0
            };

            mf.mesh = new Mesh();
            mf.mesh.vertices = vertices;
            mf.mesh.triangles = triangles;

            MeshRenderer mr = child.AddComponent<MeshRenderer>();
            mr.material = frustumMat;
        }

        Triangles[0].GetComponent<MeshFilter>().mesh.vertices = new[]
        {
            transform.position,
            farTopLeft,
            farTopRight
        };
        Triangles[0].GetComponent<MeshFilter>().mesh.normals = new[]
        {
            new Plane(transform.position, farTopLeft, farTopRight).normal,
            new Plane(transform.position, farTopLeft, farTopRight).normal,
            new Plane(transform.position, farTopLeft, farTopRight).normal
        };

        Triangles[1].GetComponent<MeshFilter>().mesh.vertices = new[]
        {
            transform.position,
            farTopRight,
            farBotRight
        };
        Triangles[1].GetComponent<MeshFilter>().mesh.normals = new[]
        {
            new Plane(transform.position, farTopRight, farBotRight).normal,
            new Plane(transform.position, farTopRight, farBotRight).normal,
            new Plane(transform.position, farTopRight, farBotRight).normal
        };

        Triangles[2].GetComponent<MeshFilter>().mesh.vertices = new[]
        {
            transform.position,
            farBotRight,
            farBotLeft
        };
        Triangles[2].GetComponent<MeshFilter>().mesh.normals = new[]
        {
            new Plane(transform.position, farBotRight, farBotLeft).normal,
            new Plane(transform.position, farBotRight, farBotLeft).normal,
            new Plane(transform.position, farBotRight, farBotLeft).normal
        };

        Triangles[3].GetComponent<MeshFilter>().mesh.vertices = new[]
        {
            transform.position,
            farBotLeft,
            farTopLeft
        };
        Triangles[3].GetComponent<MeshFilter>().mesh.normals = new[]
        {
            new Plane(transform.position, farBotLeft, farTopLeft).normal,
            new Plane(transform.position, farBotLeft, farTopLeft).normal,
            new Plane(transform.position, farBotLeft, farTopLeft).normal
        };
    }
}