How to package AssetBundle

AssetBundle What is it? ？

AssetBundle It's a Archive file , contain Can be loaded at runtime Of Platform specific Resources for （ Model 、 texture 、 The precast body 、 scene ）

AssetBundle Sure Express the dependency between each other ,AssetBundle A Materials in can reference AssetBundle B Texture in

For effective delivery through the network , You can choose built-in algorithm to compress according to the requirements of use cases （LZMA,LZ4）

 LZMA Algorithm : The compressed package is smaller , Longer load time . You need to decompress the whole before using . Once decompressed , This package will use LZ4 Recompress . At this time make                         There is no need to decompress the whole resource .         

 LZ4 Algorithm ： The loading time is similar to that without compression , There is no need to decompress the whole before use .

1. For downloadable content , Reduce the initial installation size .

2. Load resources optimized for the end-user platform , Reduce memory pressure when running

3. Need to update some simple things , Such as festival activities UI It needs to be changed , have access to AssetBundle Package to update without requiring users to download the game again

AssetBundle What's in it ？

Contains the actual files on the disk , be called AssetBundle The archive , It can be regarded as a container , You can include other files . These documents fall into two categories ：

1.serialized file（ Serialized files ）： Resources are broken up and placed in an object , Finally, the unification is written into a separate file （ only one ）

resource files（ Source file ）： Resource files are just for some resources （ texture , Audio ） Separately stored binary data blocks , Allows us to effectively load them from disk on another thread

2.AssetBundle object ： Objects loaded from a specific compressed package through code , This object contains all the contents that we originally added to this compressed package , We can use this object to load and use

AssetBundle Usage flow ： 

1. Of a specified resource AssetBundle attribute

In the resources to be packaged Inspector Specified in the panel AssetBundle Properties of

 

2. structure AssetBundle package

establish Editor Folder , Create one in the folder C# Script , The code is ：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System.IO;

public class CreateAssetBundles{
    /*MenuItem Property allows you to add menu items to the main menu and the inspector context menu . 
     This attribute turns any static function into a menu command . Only static functions can use this MenuItem attribute */
    [MenuItem("Assets/Build AssetBundles")]
    
    static void BulidAllAssetBundles()
    {
        string dir = "AssetBundles";
        if (Directory.Exists(dir) == false)
            Directory.CreateDirectory(dir);
        // The output path   Package compression format   Packaged to the platform 
        BuildPipeline.BuildAssetBundles(dir, BuildAssetBundleOptions.None, BuildTarget.StandaloneWindows64);
    }
}

BuildAssetBundleOptions.None： Use LZMA Algorithm compression        

BuildAssetBundleOptions.UncompressedAssetBundle： Uncompressed , Bao Da , Load fast         BuildAssetBundleOptions.ChunkBasedCompression： Use LZ4 Compress
 

adopt  MenuItem We are Unity Of Asset Options create Bulid AssetBundles Option calls this code to package resources into dir In the specified directory

We can see the package in the project file AssetBundles It's packed

After the game is released, you need AssetBundle Package on the server , Then we need to download the game from the server AssetBundle Load the package , Due to frequent debugging during development , We load the package locally

3. Locally, yes AssetBundle Load and use ： Create an empty object mount script in the game scene , The content is ：

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

public class LoadWallFormFile : MonoBehaviour {
	// Use this for initialization
	void Start () {
        //1. load AssetBundle
        AssetBundle ab = AssetBundle.LoadFromFile("AssetBundles/wall.dz");
        //2. from AssetBundle Get the resource to load 
        GameObject wallPrefab = ab.LoadAsset<GameObject>("Wall");
        //3. Instantiate resources into the scene 
        Instantiate(wallPrefab);
	}
}

In this way, we can see the things we packed before in the scene

AssetBundle Group strategy ：

Of a specified resource AssetBundle Tags are actually a kind of classification of resources

1. Frequently updated resources are placed in a separate package , Separate from infrequently updated packages
2. Resources that need to be loaded at the same time ( Small resources ) In a bag
3. Resources shared by other packages are put in one package ( Reduce AB The size of the bag )
4. Two versions of the same resource can be distinguished by suffixes

For the third point , There are cases of how to package shared resources ：

As shown in the figure, there is a sphere and cube, All use the name wood The material of

If we don't use dependency packaging , Then the situation on the left in the figure below will appear ,AB Bao Zhongwei sphere and cube In the packed file , It contains the same maps and materials , If we use the dependency packaging scheme on the right , You can optimize the size of the package

First of all, we will share the map and material AssetBundle Set to share

Again cube and sphere Set up one AssetBundle Properties of , Random names

Observe the files packaged again ,cube and sphere The file size of is very small ,share The size of is the largest

If there is no resource setting to be shared AssetBundle Label words , It will be packaged as shown in the figure below ,cube and sphere Both contain the same set of maps and materials