using UnityEngine;
using System.Collections;

public class MeshTest : MonoBehaviour
{
    void Start()
    {
        MeshFilter mf = GetComponent<MeshFilter>();
        Mesh mesh = new Mesh();
        mf.mesh = mesh;

        mesh.vertices = new Vector3[3] { new Vector3(0, 0, 0), new Vector3(0, 1, 0), new Vector3(1, 1, 0) };
        mesh.uv = new Vector2[3] { new Vector2(0, 0), new Vector2(0, 1), new Vector2(1, 1) };
        mesh.triangles = new int[3] { 0, 1, 2 };
    }
}

using UnityEngine;
using System.Collections;

public class MyMesh : MonoBehaviour
{
    void Start()
    {
        MeshFilter mf = GetComponent<MeshFilter>();
        Mesh mesh = new Mesh();
        mf.mesh = mesh;
        //顶点[决定绘制出来图片的scale]
        mesh.vertices = new Vector3[4] { new Vector3(0, 0, 0), new Vector3(1, 0, 0), new Vector3(0, 1, 0), new Vector3(1, 1, 0) };
        //三角形顶点索引的顺序[3的倍数]
        mesh.triangles = new int[6] { 0, 2, 1, 2, 3, 1 };
        //法线
        mesh.normals = new Vector3[4] { new Vector3(0, 0, -1), new Vector3(0, 0, -1), new Vector3(0, 0, -1), new Vector3(0, 0, -1), };
        //uv纹理坐标
        mesh.uv = new Vector2[4] { new Vector2(0, 0), new Vector2(1, 0), new Vector2(0, 1), new Vector2(1, 1) };
    }
}