30行代码，在Unity制造一个风中飘舞的旗帜

rustum · 发表于 2022-3-10 16:57

0.效果

1.代码

using UnityEngine;
using DG.Tweening; //DoTween补间库，可以到AssetStore下载

[RequireComponent(typeof(MeshFilter), typeof(MeshRenderer))]
public class ProceduralMesh : MonoBehaviour
{
[SerializeField] private int xValue, yValue;

private MeshFilter meshFilter;
private Mesh mesh;
private Vector3[] vertices;
private Vector3[,] vertices2dArray;
private Vector3[,] vertices2dArray_Origin;

private float rate = -1f;

private void Start()
{
      meshFilter = GetComponent<MeshFilter>();
      DOTween.To(() => rate, x => rate = x, 6, 2).SetLoops(-1, LoopType.Yoyo).SetEase(Ease.InOutSine);
      GenerateMesh();
}

private void Update()
{
      //动画
      for (int x = 0; x <= xValue; x++)
      {
         for (int y = yValue; y > -1; y--)
         {
            Vector3 pos = vertices2dArray_Origin[x, y]
                  + new Vector3(Mathf.Cos((270 + (yValue - y) * rate) * Mathf.Deg2Rad), 0);
            vertices2dArray[x, y] = pos;
         }
      }

      for (int index = 0, y = 0; y <= yValue; y++)
      {
         for (int x = 0; x <= xValue; x++, index++)
         {
            vertices[index] = vertices2dArray[x, y];
         }
      }

      mesh.vertices = vertices;
}

private void GenerateMesh()
{
      //顶点 + UV
      vertices = new Vector3[(xValue + 1) * (yValue + 1)];
      vertices2dArray = new Vector3[xValue + 1, yValue + 1];
      vertices2dArray_Origin = new Vector3[xValue + 1, yValue + 1];
      Vector2[] uv = new Vector2[vertices.Length];
      for (int i = 0, y = 0; y <= yValue; y++)
      {
         for (int x = 0; x <= xValue; x++, i++)
         {
            vertices = new Vector2(x, y);
            vertices2dArray[x, y] = new Vector2(x, y);
            vertices2dArray_Origin[x, y] = new Vector2(x, y);
            uv = new Vector2((float)x / xValue, (float)y / yValue);
         }
      }
      //三角形(ti：TriangleIndex，vi：VerticesIndex)
      int[] triangles = new int[xValue * yValue * 6];
      for (int ti = 0, vi = 0, y = 0; y < yValue; y++, vi++)
      {
         for (int x = 0; x < xValue; x++, ti += 6, vi++)
         {
            triangles[ti] = vi;
            triangles[ti + 3] = triangles[ti + 2] = vi + 1;
            triangles[ti + 4] = triangles[ti + 1] = vi + xValue + 1;
            triangles[ti + 5] = vi + xValue + 2;
         }
      }

      mesh = new Mesh() { vertices = vertices, triangles = triangles, uv = uv, name = &#34;Flag&#34; };
      meshFilter.mesh = mesh;
}
}
2.简析

首先生成一个正确的网格。

每帧从旗帜的上方到下方依次改变顶点位置。

创建一个pingpong型的补间数值，用这个数值驱动顶点位移，形成动画。

注：另外需要注意的是，这种效果在正常情况下或许会选择在GPU实现来达到一个最佳性能，但是这篇短文是一个关于Mesh变形的简短示例，所以就用了一个这样的例子，请大家辩证看待。一来为初次接触Mesh编程的同学带来一个最最直观的示例，知道了Mesh编程究竟能做什么。二来为之后真正的Mesh变形+物理碰撞系列文章做一个基础铺垫。

3.源文件地址

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[笔记] 30行代码，在Unity制造一个风中飘舞的旗帜

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