csharp 把相机朝向的物体的面向相机面剔除

Posted 2021-05-12

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

public class HideOneSide : MonoBehaviour
{
    public List<Transform> VerticeTransforms;
    private Mesh _mesh;
    private MeshFilter _meshFilter;
    private MeshRenderer _meshRenderer;
    public bool EnableHideSide = false;
	// Use this for initialization
	void Start ()
	{

	    CreateMesh();

	}


    void CreateMesh()
    {
        if(gameObject.GetComponent<MeshFilter>()==null)
            _meshFilter = gameObject.AddComponent<MeshFilter>();
        _mesh = new Mesh();
        UpdateMesh();
        _mesh.RecalculateNormals();
        _meshFilter.mesh = _mesh;
        if(gameObject.GetComponent<MeshRenderer>()==null)
            _meshRenderer = gameObject.AddComponent<MeshRenderer>();
    }

    void UpdateMesh()
    {
        CreateVertices();
        CreateTriangles();
    }

    void Update()
    {
        UpdateMesh();

        if(EnableHideSide)
            HideFrontSide();
    }

    void HideFrontSide()
    {
        Vector3[] vertices = _mesh.vertices;
        Vector3 a = vertices[0];
        Vector3 b = vertices[1];
        Vector3 c = vertices[2];
        Vector3 worldNormal = Vector3.Cross(b - a, c - b);
        worldNormal = Camera.main.projectionMatrix*worldNormal;
        float angle = Vector3.Angle(worldNormal, Camera.main.transform.forward);
        if (Mathf.Abs(angle) < 90)
        {
           
        }
        else
        {
            _mesh.triangles = null;
        }
    }

    void CreateVertices()
    {
        if (VerticeTransforms != null)
        {
            List<Vector3> vertices = new List<Vector3>();
            for (int i = 0; i < VerticeTransforms.Count; i++)
            {
                vertices.Add(VerticeTransforms[i].transform.localPosition);
            }
            _mesh.SetVertices(vertices);

        }
    }

    void CreateTriangles()
    {
        List<int> triangles = new List<int>();
        for (int i = 0; i < VerticeTransforms.Count/3; i ++)
        {
            triangles.Add(3 * i);
            triangles.Add(3 * i + 1);
            triangles.Add(3 * i + 2);
        }
        
        _mesh.SetTriangles(triangles,0);
    }
}