开始收集

YooAsset.Editor.ShaderVariantCollector.Run

创建临时场景

// 创建临时测试场景
			CreateTempScene();

			_steps = ESteps.Prepare;
			EditorApplication.update += EditorUpdate;

准备阶段

反射调用ShaderUtil.ClearCurrentShaderVariantCollection清空当前项目搜集到的变体，我们需要重新搜集一次；

EditorTools.InvokeNonPublicStaticMethod(typeof(ShaderUtil), "ClearCurrentShaderVariantCollection");

如何反射调用

		/// <summary>
		/// 调用私有的静态方法
		/// </summary>
		/// <param name="type">类的类型</param>
		/// <param name="method">类里要调用的方法名</param>
		/// <param name="parameters">调用方法传入的参数</param>
		public static object InvokeNonPublicStaticMethod(System.Type type, string method, params object[] parameters)
		{
			var methodInfo = type.GetMethod(method, BindingFlags.NonPublic | BindingFlags.Static);
			if (methodInfo == null)
			{
				UnityEngine.Debug.LogError($"{type.FullName} not found method : {method}");
				return null;
			}
			return methodInfo.Invoke(null, parameters);
		}

收集全部材质球

YooAsset.Editor.ShaderVariantCollector.GetAllMaterials
所有收集器的依赖asset

// 获取所有打包的资源
			CollectResult collectResult = AssetBundleCollectorSettingData.Setting.GetPackageAssets(EBuildMode.DryRunBuild, _packageName);
			foreach (var assetInfo in collectResult.CollectAssets)
			{
				string[] depends = AssetDatabase.GetDependencies(assetInfo.AssetPath, true);
				foreach (var dependAsset in depends)
				{
					if (allAssets.Contains(dependAsset) == false)
						allAssets.Add(dependAsset);
				}

收集所有依赖asset的材质球

List<string> allMaterial = new List<string>(1000);
			foreach (var assetPath in allAssets)
			{
				System.Type assetType = AssetDatabase.GetMainAssetTypeAtPath(assetPath);
				if (assetType == typeof(UnityEngine.Material))
				{
					allMaterial.Add(assetPath);
				}

收集变体，摄像机照射所有材质球一遍

变体收集，每次只处理最大1000个材质球，超过的，等下一批再处理
YooAsset.Editor.ShaderVariantCollectorSetting.ProcessCapacity = 1000
每次处理一批时，总材质球列表_allMaterials去掉0-count，然后处理当前的range

int count = Mathf.Min(_processMaxNum, _allMaterials.Count);
				List<string> range = _allMaterials.GetRange(0, count);
				_allMaterials.RemoveRange(0, count);

在场景中创建一堆sphere几何体，并排列整齐，然后把渲染相机对齐它们，并保证它们都可以看见；
分批次把这些材质资源赋予这些sphere几何体，渲染100ms；

完成处理

变体收集到路径YooAsset.Editor.ShaderVariantCollectorSetting.SavePath = “Assets/MyShaderVariants.shadervariants”
反射调用ShaderUtil.SaveCurrentShaderVariantCollection保存到一个整体变体集合资源中去

EditorTools.InvokeNonPublicStaticMethod(typeof(ShaderUtil), "SaveCurrentShaderVariantCollection", savePath);

输出文件
MyShaderVariants.shadervariants会打包进入unityshaders.bundle包里

输出json，可以查看keyword做相应的剔除

AssetPath": "Resources/unity_builtin_extra",
            "ShaderName": "Standard",
            "ShaderVariantElements": [
                {
                    "PassType": 4,
                    "Keywords": [
                        "DIRECTIONAL",
                        "LIGHTPROBE_SH",
                        "SHADOWS_SCREEN",
                        "SHADOWS_SPLIT_SPHERES"
                    ]
                },
                {
                    "PassType": 4,
                    "Keywords": [
                        "DIRECTIONAL",
                        "LIGHTPROBE_SH",
                        "SHADOWS_SCREEN",
                        "SHADOWS_SPLIT_SPHERES",
                        "_EMISSION"
                    ]
                },

打包时去掉keyword代码示例

public class StripInstancingOnKeyword : IPreprocessShaders
{
    public int callbackOrder
    {
        //多个回调处理的处理顺序
        get { return 0; }
    }

    //在执行打包assetbundle会处理
    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> inputData)
    {
        Debug.Log(string.Format("shader：{0}", shader.name));

        //反向遍历，有利于删除
        for (int i = inputData.Count - 1; i >= 0; i--)
        {
            ShaderCompilerData input = inputData[i];
            //Global And Local Keyword
            if (input.shaderKeywordSet.IsEnabled(new ShaderKeyword("DIRECTIONAL")) || 
                input.shaderKeywordSet.IsEnabled(new ShaderKeyword(shader, "DIRECTIONAL")))
            {
                Debug.Log(string.Format("剔除shader：{0}，变体{1}", shader.name, "DIRECTIONAL"));
                inputData.RemoveAt(i);
            }
        }
    }
}