unity 显示mipmaplevel

https://docs.unity3d.com/ScriptReference/Texture2D.SetPixels.html

显示mipmaplevel 需要贴图可读写不压缩

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    void Start()
    {
        Renderer rend = GetComponent<Renderer>();

        // duplicate the original texture and assign to the material
        Texture2D texture = Instantiate(rend.material.mainTexture) as Texture2D;
        rend.material.mainTexture = texture;

        // colors used to tint the first 3 mip levels
        Color[] colors = new Color[3];
        colors[0] = Color.red;
        colors[1] = Color.green;
        colors[2] = Color.blue;
        int mipCount = Mathf.Min(3, texture.mipmapCount);

        // tint each mip level
        for (int mip = 0; mip < mipCount; ++mip)
        {
            Color[] cols = texture.GetPixels(mip);
            for (int i = 0; i < cols.Length; ++i)
            {
                cols[i] = Color.Lerp(cols[i], colors[mip], 0.33f);
            }
            texture.SetPixels(cols, mip);
        }
        // actually apply all SetPixels, don't recalculate mip levels
        texture.Apply(false);
    }
}