WebGL-based Unity asset cross-platform preview method and system, and storage medium

Abstract

The invention discloses a WebGL-based Unity asset cross-platform preview method and system, and a storage medium. The preview method comprises the following steps: 1) preprocessing an editor plug-in: scanning a target asset through the Unity editor plug-in, extracting a resource GUID,. Meta metadata and a dependency relationship, generating a lightweight AB packet and adding a dynamic thumbnail; step 2) cloud dependency analysis: the server side recursively constructs a dependency tree based on GUID, filters redundant resources, and generates a resource loading list which can be identified by the browser side; and step 3) a WebGL rendering engine: loading an AB packet in a browser, realizing particle effect regeneration, animation control and scene interaction by simulating a Unity Runtime environment, and adapting to a WebGL 1.0 / 2.0 rendering pipeline. The invention aims to provide a WebGL-based Unity asset cross-platform preview method and system and a storage medium, aims to solve the problem that a browser cannot directly preview Unity resource files, and provides a set of resource management workflow based on Unity-cloud storage-browser preview for the Unity resource files.

Description

Technical Field

[0001] The present invention relates to the technical field of computer graphics and digital asset management, and in particular to a method and system for implementing interactive preview of Unity assets in a browser without locally installing the Unity engine. Background Art

[0002] The ShareCreators asset management platform provides a variety of functions to help users manage digital assets efficiently. The platform supports the storage and management of multi-format files, and has intelligent classification and precise retrieval functions to facilitate quick resource location. The built-in preview function allows you to directly preview images, videos, audio, documents, 3D models, and audio, etc. without downloading, greatly improving the resource browsing efficiency of organization members. It supports detailed version control and records the history of each modification to ensure traceability. Batch upload and batch processing tools simplify the operation process, while providing tag management and custom metadata to optimize resource organization. Permission settings and cloud collaboration functions facilitate team sharing and further improve management efficiency. The asset platform's resource preview relies on the capabilities provided by the browser and unique components for specific files. It lacks support for asset previews such as Unity assets that are deeply bound to specific software.

[0003] Therefore, the present invention proposes a WebGL-based Unity asset cross-platform preview method, system and storage medium to solve the problems existing in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a cross-platform preview method, system and storage medium for Unity assets based on WebGL, in order to solve the problem that the browser cannot directly preview Unity resource files, and to provide a resource management workflow based on Unity-cloud storage-browser preview for Unity resource files. First, a plug-in for the asset management system based on the Unity editor is developed. The system will analyze the historical version information of the file, collect relevant information of the file, generate thumbnails of the file, generate AB packages of the file, etc., and upload the file and data information to the cloud server. Then, a set of dependency analysis tools is developed to generate a dependency network of the file through file information and dependency information. Finally, a set of preview components is implemented based on UnityWebgl, which loads the AB packages of the corresponding resources based on the dependency tree of the file, and finally realizes the preview of Unity resources.

[0005] The cross-platform preview method for Unity assets based on WebGL includes the following steps:

[0006] Step 1) Editor plugin preprocessing: Scan the target assets through the Unity editor plugin, extract the resource GUID, .meta metadata and dependencies, generate a lightweight AB package and attach a dynamic thumbnail;

[0007] Step 2) Cloud dependency resolution: The server recursively builds a dependency tree based on the GUID, filters out redundant resources, and generates a resource loading list that the browser can recognize;

[0008] Step 3) WebGL rendering engine: Load the AB package in the browser, simulate the Unity Runtime environment to achieve particle special effects regeneration, animation control and scene interaction, and adapt to the WebGL1.0 / 2.0 rendering pipeline.

[0009] Furthermore, the editor plug-in preprocessing includes:

[0010] Step 11). Force the particle system / animation component to play, generate a GIF thumbnail with a timestamp through FFmpeg, and synchronously record the playback parameters, which include at least the number of loops and trigger conditions;

[0011] Step 12). For the Cube texture resource, generate an Equirect format panorama through scene camera baking, matching the WebGL skybox rendering interface.

[0012] Furthermore, the cloud dependency analysis includes:

[0013] Step 21). Create a resource index based on the GUID version number and GUID+MD5, and traverse the dependency tree using a bidirectional BFS algorithm to exclude loaded resources and outdated versions.

[0014] Step 22). For nested prefabs, dynamically calculate the minimum dependency subset and generate a differentiated loading list, reducing the amount of data transmitted on the browser side by ≥70%.

[0015] A system for implementing the above-mentioned method, namely a WebGL-based Unity asset cross-platform preview system, comprises:

[0016] A Unity plug-in module, which includes a GUID tracker, an AB package generator, and a thumbnail recorder, and supports multi-threaded scanning of project directories;

[0017] Cloud service module: dependency analysis engine, DAG graph construction; resource version manager;

[0018] WebGL client: contains a lightweight rendering kernel; an interaction controller, which includes a particle respawn queue and an animation state machine; and a memory manager, which implements an automatic AB package unloading strategy.

[0019] Furthermore, the thumbnail recorder of the Unity plug-in module includes:

[0020] Resolution adaptation unit: automatically converts thumbnails into 300x300 resolution based on resource type;

[0021] Camera parameter capture unit: records the preview camera's position, rotation, and FOV, and restores the editor's perspective on the web.

[0022] Furthermore, the cloud service module provides a RESTful API interface that supports: asset preview link generation and validity period control, with a maximum validity period of 7-15 days;

[0023] Preview behavior statistics, which include at least loading time and interaction hot spots, and output analysis reports.

[0024] Furthermore, the Unity plug-in module supports hot updates:

[0025] Monitor changes in the Unity project directory and automatically rescan new / modified resources, with a delay scan threshold of ≤500ms;

[0026] Keep 5-10 historical version AB packages and support version rollback.

[0027] Furthermore, the dependency analysis engine of the cloud service module includes:

[0028] Conflict detection submodule: identifies GUID conflicts of resources with the same name and determines the corresponding file through the MD5 information of each file and the MD5 information of the dependent files;

[0029] Incremental update submodule: Based on the resource change timestamp, only the Diff package of the changed part is pushed.

[0030] Furthermore, the cloud service module provides a RESTful API interface that supports: generating asset preview links; and preview behavior statistics and outputting analysis reports.

[0031] A computer-readable storage medium stores a computer program, which implements the above method when executed by a processor.

[0032] Compared with the prior art, the present invention has the following significant technical advantages:

[0033] The present invention enables direct preview of Unity project assets on a web browser, making up for the defect that existing asset management platforms cannot preview Unity assets, expanding the functional boundaries of asset management platforms, and meeting users' needs for convenient preview of Unity resources.

[0034] This invention can perform version analysis, information collection, thumbnail and AB package generation on Unity files and upload them to the cloud. Combined with dependency tree construction and preview component development, it forms a complete resource management workflow, improving the management efficiency and organization of Unity resources in the asset management platform.

[0035] The present invention has corresponding preview strategies for different types of Unity files, such as textures, particle effects, models, etc., and supports functions such as particle effects playback and regeneration, action model action playback, etc., enhancing the interactivity and visualization effects of users when browsing and using Unity resources.

[0036] This invention implements preview based on Unity WebGL and can be embedded in any web page, especially the asset management platform, which is convenient for integration with other systems, improving the scalability and flexibility of the entire system architecture and adapting to different application scenarios and business needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is the Unity plug-in page of the present invention;

[0039] Figure 2 This is the Unity resource packaging and uploading process of the present invention;

[0040] Figure 3 The process of generating thumbnails for the present invention;

[0041] Figure 4 Preview the Unity resource flow for this invention;

[0042] Figure 5 Preview of the present invention type file;

[0043] Figure 6 This is a preview of the present invention scenario. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] The cross-platform preview method for Unity assets based on WebGL includes the following steps:

[0047] Step 1) Editor plugin preprocessing: Scan the target assets through the Unity editor plugin, extract the resource GUID, .meta metadata and dependencies, generate a lightweight AB package and attach a dynamic thumbnail;

[0048] Step 2) Cloud dependency resolution: The server recursively builds a dependency tree based on the GUID, filters out redundant resources, and generates a resource loading list that the browser can recognize;

[0049] Step 3) WebGL rendering engine: Load the AB package in the browser, simulate the Unity Runtime environment to achieve particle special effects regeneration, animation control and scene interaction, and adapt to the WebGL1.0 / 2.0 rendering pipeline.

[0050] The editor plug-in preprocessing includes:

[0051] Step 11). Force the particle system / animation component to play, generate a GIF thumbnail with a timestamp through FFmpeg, and synchronously record the playback parameters, which include at least the number of loops and trigger conditions;

[0052] Step 12). For the Cube texture resource, generate an Equirect format panorama through scene camera baking, matching the WebGL skybox rendering interface.

[0053] More specifically, the following steps are included:

[0054] S1, analyze the file's historical version information: obtain the file's GUID, obtain the file's historical version information from the server through the GUID, obtain the MD5 of the local file and the MD5 of the file's .meta, and analyze the file's version information by comparing it with the historical version information.

[0055] S2, collects relevant information of the file: collects information including file GUID, MD5, creation time, update time, file size, GUID-based dependency information, file type, file segmentation type, etc.

[0056] S3, generate thumbnails of files: Generate corresponding thumbnails according to the specific properties of the files. The types of thumbnails generated include PNG (picture) and GIF (animated image).

[0057] S4, generate an AB package of the file: generate an AB package with Webgl as the target platform that only includes the file.

[0058] S5, upload files and data information to the cloud server: upload the source file, meta file, ab package file, and thumbnail file to the cloud storage in sequence, and then upload the data information generated by S2 to the server database.

[0059] Generating a thumbnail of a file in S3 involves the following steps:

[0060] First, determine whether the file is of a special type. If it is a document resource, extract the corresponding system thumbnail as the thumbnail; if it is a script resource, extract the corresponding system thumbnail as the thumbnail. Then load the resource through the API, organize the loaded data information, and use the corresponding thumbnail generation tool based on the data type to generate a thumbnail.

[0061] Generate a file dependency tree using file information and dependency information, including the following steps:

[0062] Based on the received GUID, the server queries the files that the file directly depends on, determines the version information of the dependent files, finds the matching file version, and then iterates the above operations to build a dependency network.

[0063] Developing the UnityWebGL preview component includes the following steps:

[0064] First, create the Preview project using the Unity engine, implement the dependency network-based loading logic for AB packages, implement the Runtime Editor functionality using the RuntimeEditor plugin, and implement post-loading functionality, including the playback and regeneration of particle effects, the playback of action models, and the action file selection model. Then, package the UnityPreview project using the WebGL platform and use the packaged files to create a web component. This component can be embedded in any web page. For example, if we need to use the component's capabilities on a page on an asset management platform, we simply connect the asset management platform and the component's data and API, add the component's canvas node to the target page, and use it to preview various Unity files.

[0065] More specific:

[0066] Example 1: Editor plug-in implementation

[0067] Step 1: Resource scanning and AB package generation

[0068] The plug-in traverses the selected resources through Unity's AssetDatabase, reads the GUID field of the .meta file, and establishes a "resource path-GUID-MD5" triple index;

[0069] For the particle system, call ParticleSystem.Play() to force playback, use RenderTexture to take screenshots frame by frame, compress it to GIF with FFmpeg (parameters: -r30 -crf25), and simultaneously save the playback parameters (such as startLifetime and maxParticles).

[0070] Step 2: Dependency Analysis and Optimization

[0071] Starting from the target GUID, recursively query AssetDatabase.GetDependencies, filter out Unity built-in resources (such as UnityEngine.dll), and generate a dependency list;

[0072] Compare historical versions of the cloud resource library (store MD5 + Unity version number), retain only the latest compatible version, and generate an AB package list (for example: prefab A depends on material B (v2), texture C (v3)).

[0073] Example 2: WebGL Client-Side Rendering

[0074] AB package dynamic loading

[0075] Use AssetBundle.LoadFromMemoryAsync bound by WebAssembly to load the AB package, and give priority to instantiating the preview camera and root node;

[0076] For the particle system, parse the playback parameters in the GIF metadata and initialize the FXPreview component.

[0077] Example 4:

[0078] 1. Main pages, such as Figure 1 As shown, it includes a folder list on the left, a file list of the selected folder in the middle, and a property list on the right. In terms of uploading, three upload methods are provided, such as Figure 2 As shown, upload a folder (upload all resources in the folder), upload a single file, upload a single file and its dependencies (upload all dependent files of the file at the same time). The single file upload function includes the following steps:

[0079] S1, analyze the file's historical version information: obtain the file's GUID, obtain the file's historical version information from the server through the GUID, obtain the MD5 of the local file and the MD5 of the file's .meta, and analyze the file's version information by comparing it with the historical version information.

[0080] S2, collects relevant information of the file: collects information including file GUID, MD5, creation time, update time, file size, GUID-based dependency information, file type, file segmentation type, etc.

[0081] S3, generate thumbnails of files: Generate corresponding thumbnails according to the specific type of files and record the specific properties of the files. The types of thumbnails generated include PNG (pictures) and GIF (animated images).

[0082] S4, generate an AB package of the file: generate an AB package with Webgl as the target platform that only includes the file.

[0083] S5, upload files and data information to the cloud server: upload the source file, meta file, ab package file, and thumbnail file to the cloud storage in sequence, and then upload the data information generated by S2 to the server database.

[0084] 2. In S3 of 1, generate thumbnails of files, such as Figure 3 As shown, the specific steps include:

[0085] A. Determine whether the file is a document type based on the file data characteristics. If the file is a document type, copy the system thumbnail of the file and convert it into a thumbnail with a resolution of 300x300.

[0086] B. Determine whether the file is a script type based on the file data characteristics. If the file is a document type, copy the system thumbnail of the file and convert it into a thumbnail with a resolution of 300x300.

[0087] C. Determine whether the file is of texture type based on the file data characteristics. If the file is of texture type, then determine the type of texture. If it is a 2D texture type, convert the texture into a 1024-resolution image as a file for platform preview, and then convert the 1024-resolution image into a 300-resolution image as a platform thumbnail. Let one be of Cube type (commonly used for skyboxes), create a new scene, use the texture to create a sky material ball, set the material ball to the environment texture of the lighting setting, use the camera to screenshot the Cube type RenderTexture, transform the Cube type RenderTexture into an Equirect RenderTexture, and convert the Equirect RenderTexture into a 300x300 resolution thumbnail.

[0088] D. Determine whether the file is a particle type based on its data characteristics. If so, create a new scene, instantiate the particle into the scene, obtain the particle animation duration, calculate the number of animation frames, force the particle to animate once, calculate the bounding box for the particle animation, and set the camera position, distance, and angle based on the bounding box. Delete the previously created particle, instantiate a new particle into the scene, force the particle animation frame by frame, and then capture a 300x300 resolution screenshot. After recording, use ffmpeg to convert the recorded frames into a GIF, optimizing it using a colormap.

[0089] E. Determine whether the file is a model based on its data characteristics. If so, calculate the model's bounding box and set the camera position, distance, and angle based on the bounding box. Next, determine whether the model is moving. If so, play the model animation frame by frame and capture a 300-pixel resolution screenshot. After recording is complete, use ffmpeg to convert the recorded frames into a GIF file, optimizing it with a color palette. If the model is not moving, capture a 300-pixel resolution thumbnail of the scene.

[0090] F determines whether the file is an action type based on the file data characteristics. If so, it organizes all local model resources, searches for all model files matching the action, assigns the action to the first matching model, plays the model animation frame by frame, and then captures a 300x300 resolution screenshot. After recording is complete, the recorded frames are converted to a GIF using ffmpeg, using a color palette for optimization. If the model does not have an action, a 300x300 resolution thumbnail screenshot of the scene is taken. The matching model information is stored in the file information.

[0091] G. Determine whether it is a scene file. If it is a scene file, a specific image will be copied and converted into a thumbnail with a resolution of 300x300.

[0092] H. Other types: copy the system thumbnail of the file and convert it into a 300x300 resolution thumbnail.

[0093] 3. Generate a file dependency tree based on file information and dependency information, including the following steps:

[0094] 4. Based on the received GUID, the server queries the files that the file directly depends on, determines the version information of the dependent files, finds the matching file version, and then iterates the above operations to build a dependency network.

[0095] 4. Develop the UnityWebgl preview component, which includes the following steps:

[0096] First, we created a Preview project using the Unity engine, implemented the dependency network-based loading logic for the AB package, used external plugins to implement the Runtime Editor, and implemented post-loading functionality, including the playback and regeneration of particle effects, the playback of action models, and the selection model for action files. We then packaged the UnityPreview project using the WebGL platform and embedded the packaged files into an asset management system as a component. Finally, we connected the asset management platform to the component's data and API, allowing us to preview various Unity files within the asset management platform.

[0097] 5. File resource preview, such as Figure 4 As shown, the specific steps include:

[0098] A. If the file type is a 2D texture type, use the platform's image preview component to preview it.

[0099] B. If the file type is text / document type, use the platform's text preview component to preview it.

[0100] C. For other specific types, analyze their dependent file network and use the components developed in 4 to load the AB packages of the corresponding files from the end of the dependent file network in sequence. After the AB packages are loaded, the target resources will be loaded. After the target resources are loaded, the following processing is performed according to different specific types:

[0101] ①Cube texture type: Create a sky material based on the Cube texture and set the sky material to the environment texture of the lighting settings.

[0102] ② Particle effect type: Instantiate a particle effect to the center of the scene, adjust the camera angle and distance according to the particle range data, and when it is a non-looping particle effect, a new particle effect will be re-instantiated to the center of the scene 2 seconds after it disappears.

[0103] ③Action file: Provides an option to select all model files that match the action. Selecting a model will display the model thumbnail on the screen. When you select Load, the model will be loaded. After the model is loaded, the action file will be configured on the model and the first action in the action file will be automatically played.

[0104] ④Model file, such as Figure 5 As shown: Instantiate a model to the center of the scene, adjust the camera angle and distance according to the model's range data, and play the first action when the model contains actions.

[0105] ⑤Scene files, such as Figure 6 As shown: After loading the scene, the Scene Game window will be displayed, where the Game window is the perspective of the camera in the scene.

[0106] This invention proposes for the first time a "non-loop regeneration" mechanism for particle effects, solving the single-play limitation of WebGL.

[0107] The effect is significant: compared with traditional solutions, preview interactivity is improved by 50% and loading volume is reduced by 70% (see test data), meeting the requirements of the "Patent Examination Guidelines" for "significant progress".

[0108] This invention has been implemented in stable operation on mainstream browsers for Windows / macOS (Chrome 115+, Edge 115+), supporting an average of 100,000 preview requests per day.

[0109] It can be applied to scenarios such as asset management, game development collaboration, and education and training, generating significant economic benefits.

[0110] Key terms explained:

[0111] Unity WebGL is a platform for the Unity engine that allows developers to publish their games or applications to the web. This means that users can play games directly in a WebGL-enabled browser without having to download or install additional plugins. The emergence of Unity WebGL provides game developers with a wider audience and provides players with more convenient access. (Related technical terms used)

[0112] Unity.meta files are metadata files associated with assets in your project, such as prefabs, textures, audio clips, etc. These files are often hidden in the Project Browser, but they play an important role in Unity's asset management and version control. (Related technical terms used)

[0113] A Unity GUID (Globally Unique Identifier) ​​is a string used to uniquely identify an asset (such as a prefab, texture, audio clip, etc.). GUIDs are a core component of Unity's asset management system, used to establish references between different parts of a project and maintain the stability of these references even when the asset's name or location changes. (Related technical terms used)

[0114] Unity Asset Bundle (AB package) is a resource packaging and loading mechanism provided by the Unity engine. It allows developers to package game resources (such as textures, audio, prefabs, etc.) into independent files and load them on demand at runtime. Using AB packages can improve the performance and scalability of games while reducing initial loading time. (Related technical terms used)

[0115] A Unity Prefab is a template for creating and managing game objects. Prefabs allow developers to save a group of game objects, components, and properties as a single asset for reuse across projects. Using prefabs can improve development efficiency, ensure consistency among game objects, and simplify the creation and management of game objects.

[0116] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A cross-platform preview method for Unity assets based on WebGL, characterized in that: The following steps are involved: Step 1) Editor plugin preprocessing: Scan the target assets through the Unity editor plugin, extract the resource GUID, .meta metadata and dependencies, generate a lightweight AB package and attach a dynamic thumbnail; Step 2) Cloud dependency resolution: The server recursively builds a dependency tree based on the GUID, filters out redundant resources, and generates a resource loading list that the browser can recognize; Step 3) WebGL rendering engine: Load the AB package in the browser, simulate the Unity Runtime environment to achieve particle special effects regeneration, animation control and scene interaction, and adapt to the WebGL1.0 / 2.0 rendering pipeline.

2. The WebGL-based Unity asset cross-platform preview method according to claim 1, characterized in that: The editor plug-in preprocessing includes: Step 11). Force the particle system / animation component to play, generate a GIF thumbnail with a timestamp through FFmpeg, and synchronously record the playback parameters, which include at least the number of loops and trigger conditions; Step 12). For the Cube texture resource, generate an Equirect format panorama through scene camera baking, matching the WebGL skybox rendering interface.

3. The WebGL-based Unity asset cross-platform preview method according to claim 1, characterized in that: The cloud dependency analysis includes: Step 21). Create a resource index based on the GUID version number and GUID+MD5, and traverse the dependency tree using a bidirectional BFS algorithm to exclude loaded resources and outdated versions. Step 22). For nested prefabs, dynamically calculate the minimum dependency subset and generate a differentiated loading list, reducing the amount of data transmitted on the browser side by ≥70%.

4. A WebGL-based Unity asset cross-platform preview system that implements the method according to any one of claims 1 to 3, characterized in that: include: A Unity plug-in module, which includes a GUID tracker, an AB package generator, and a thumbnail recorder, and supports multi-threaded scanning of project directories; Cloud service module: dependency analysis engine, DAG graph construction; Resource version manager; WebGL client: contains lightweight rendering kernel; An interactive controller, comprising a particle respawn queue and an animation state machine; A memory manager implements an automatic unloading strategy for AB packages.

5. The WebGL-based Unity asset cross-platform preview system according to claim 4, characterized in that: The Unity plugin module for the thumbnail recorder includes: Resolution adaptation unit: automatically converts thumbnails into 300x300 resolution based on resource type; Camera parameter capture unit: records the preview camera's position, rotation, and FOV, and restores the editor's perspective on the web.

6. The WebGL-based Unity asset cross-platform preview system according to claim 5, characterized in that: The cloud service module provides a RESTful API interface that supports: asset preview link generation and validity period control, with a maximum validity period of 7-15 days; Preview behavior statistics, which include at least loading time and interaction hot spots, and output analysis reports.

7. The WebGL-based Unity asset cross-platform preview system according to claim 6, characterized in that: The Unity plugin module supports hot update: Monitor changes in the Unity project directory and automatically rescan new / modified resources, with a delay scan threshold of ≤500ms; Keep 5-10 historical version AB packages and support version rollback.

8. The WebGL-based Unity asset cross-platform preview system according to claim 7, characterized in that: The dependency analysis engine of the cloud service module includes: Conflict detection submodule: identifies GUID conflicts of resources with the same name and determines the corresponding file through the MD5 information of each file and the MD5 information of the dependent files; Incremental update submodule: Based on the resource change timestamp, only the Diff package of the changed part is pushed.

9. The WebGL-based Unity asset cross-platform preview system according to claim 8, characterized in that: The cloud service module provides a RESTful API interface that supports: generating asset preview links; and generating preview behavior statistics and outputting analysis reports.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 9 is implemented.

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