using UnityEngine;
using System.Collections;
using System;
public class TwistScript : MonoBehaviour {
    public float twist = 1.0f;
    public float inputSensitivity = 1.5f;
    private Vector3[] baseVertices;
    private Vector3[] baseNormals;
    private Vector3 new_pos;
       // Update is called once per frame
       void Update () {
        twist += Input.GetAxis("Horizontal") * inputSensitivity * Time.deltaTime;
        //限制扭曲範圍
        if (twist < -2)
        {
            twist = -2;
        }
        if (twist > 2)
        {
            twist = 2;
        }
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        if (baseVertices == null)
        {
            baseVertices = mesh.vertices;
        }
        if (baseNormals == null)
        {
            baseNormals = mesh.normals;
        }
        Vector3[] vertices = new Vector3[baseVertices.Length];
        Vector3[] normals = new Vector3[baseNormals.Length];
        for (int i = 0; i < vertices.Length; i++)
        {
            vertices[i] = DoTwist(baseVertices[i], baseVertices[i].y * twist);
            normals[i] = DoTwist(baseNormals[i], baseVertices[i].y * twist);
        }
        mesh.vertices = vertices;
        mesh.normals = vertices;
        mesh.RecalculateNormals();
        mesh.RecalculateBounds();
    }
    //產生扭曲
     private Vector3 DoTwist(Vector3 pos, float t)
    {
        float st = Mathf.Sin(t);
        float ct = Mathf.Cos(t);
        new_pos = Vector3.zero;
        new_pos.x = pos.x * ct - pos.z * st;
        new_pos.z = pos.x * st + pos.z * ct;
        new_pos.y = pos.y;
        return new_pos;
    }
}