介绍

Android 平台上使用的 ETC1 并不包含 Alpha 通道，因此如果想要平衡体积与质量，可以尝试将纹理拆分为两份：不包含 Alpha 通道的与包含 Alpha 通道的，然后在运行时通过 Shader 将两个纹理合并起来。

需求

  1. 支持处理场景、Prefab 中的材质
  2. 收集使用到的 Shader 以便后续改写处理
  3. 增加 Alpha 通道材质
  4. 自动替换材质的 Shader 并设置纹理字段

准备工作

需要将使用到的 Shader 编辑通道分离版本，即同时读取两张纹理显示。要注意的是需要尽量保持纹理属性名字一致，这样可以减少特殊情况处理。

处理思路

获取 Shader

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

private static void GetShadersInGameObject(GameObject go, List<string> list)
{
    var renderers = go.GetComponentsInChildren<Renderer>(true);

    foreach (var renderer in renderers)
    {
        if (renderer == null)
        {
            continue;
        }

        foreach (var material in renderer.sharedMaterials)
        {
            if (material == null || material.shader == null)
            {
                continue;
            }

            if (!list.Contains(material.shader.name))
            {
                list.Add(material.shader.name);
            }
        }
    }
}

分离 Alpha 纹理

这里要注意，分离出来 Alpha 纹理需要继承原纹理的导入选项。

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

var originTextureImporter = AssetImporter.GetAtPath(path) as TextureImporter;
var settings = originTextureImporter.GetPlatformTextureSettings("Android");
settings.textureCompression = TextureImporterCompression.Compressed;
originTextureImporter.SetPlatformTextureSettings(settings);
originTextureImporter.SaveAndReimport();

AssetDatabase.ImportAsset(alphaPath);
var textureImporter = AssetImporter.GetAtPath(alphaPath) as TextureImporter;
textureImporter.mipmapEnabled = false;
textureImporter.textureType = TextureImporterType.Default;
textureImporter.SetPlatformTextureSettings(settings);
textureImporter.SaveAndReimport();

遍历方法

由于需要修改 Renderer 的材质属性，因此按照 Renderer 逐个处理其材质即可。

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69

private static void ProcessScene()
{
    var gos = SceneManager.GetActiveScene().GetRootGameObjects();

    foreach (var go in gos)
    {
        Traverse(go.transform, ProcessTransform);
    }

    AssetDatabase.SaveAssets();
}

private static void Traverse(Transform t, System.Action<Transform> action)
{
    action.Invoke(t);

    for (int i = 0; i < t.childCount; i++)
    {
        Traverse(t.GetChild(i), action);
    }
}

private static void ProcessTransform(Transform t)
{
    var noRuntimeRenderer = t.GetComponent<NoRuntimeRenderer>();
    if (noRuntimeRenderer != null)
    {
        return;
    }

    var renderers = t.GetComponents<Renderer>();
    foreach (var renderer in renderers)
    {
        if (renderer == null)
        {
            Debug.LogError("Renderer error: " + t.name, t);
            continue;
        }

        ProcessRenderer(renderer);
    }
}

private static void ProcessRenderer(Renderer renderer)
{
    if (renderer.sharedMaterials == null || renderer.sharedMaterials.Length == 0)
    {
        Debug.LogError("Renderer has no material: " + renderer.name, renderer);
        return;
    }

    foreach (var material in renderer.sharedMaterials)
    {
        if (material == null || material.shader == null)
        {
            Debug.LogError("Material error: " + renderer.name, renderer);
            continue;
        }

        switch (material.shader.name)
        {
            case "CustomShader":
                ProcessMaterial(material, "_MainTex", renderer);
                break;
            default:
                break;
        }
    }
}

替换 Shader

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

private static void ProcessMaterial(Material material, string mainTexName, Renderer renderer)
{
    var texture = material.GetTexture(mainTexName) as Texture2D;
    var alphaTexture = ProcessTexture(texture);

    string dir = Path.GetDirectoryName(material.shader.name);
    string name = Path.GetFileName(material.shader.name);
    string alphaShaderName = dir + "_Alpha" + "/" + name;

    Texture mainTexture = material.GetTexture(mainTexName);
    Vector2 scale = material.GetTextureScale(mainTexName);
    Vector2 offset = material.GetTextureOffset(mainTexName);

    material.shader = Shader.Find(alphaShaderName);

    SetTexture(material, "_MainTex", mainTexture, scale, offset);
    SetTexture(material, "_AlphaTex", alphaTexture, scale, offset);

    EditorUtility.SetDirty(material);
}

private static void SetTexture(Material material, string propertyName,
    Texture texture, Vector2 scale, Vector2 offset)
{
    material.SetTexture(propertyName, texture);
    material.SetTextureScale(propertyName, scale);
    material.SetTextureOffset(propertyName, offset);
}