Godot AnimationTree Bone Transforms Saving Causes Version Control Pollution

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Introduction

This article addresses a significant challenge faced by Godot game developers using version control systems like Git, specifically concerning the pollution of version control history due to unintended changes in bone transformations. When working with AnimationTrees, a powerful feature in Godot for managing character animations, the engine's behavior of saving bone transformations during scene saves can lead to unnecessary commits and a cluttered version history. This article explores the issue, its causes, and potential solutions, providing developers with insights on how to maintain a clean and efficient version control workflow.

Understanding the Problem: Bone Transforms and AnimationTrees

When you are using Git/Github to version control your project, and you have many enemies/characters that use an AnimationTree, problems will occur. The AnimationTree system in Godot Engine is a robust tool for controlling complex animations in characters and other game objects. It allows developers to blend and layer animations, create state machines, and dynamically adjust animation parameters. However, the interaction between AnimationTrees and the Godot editor's scene saving mechanism can lead to version control issues. Specifically, when an AnimationTree is active, it drives the bone transformations of the associated skeleton. These transformations, representing the pose of the character at a given frame, are stored within the scene file. The core issue arises because Godot saves these bone transformations whenever a scene is saved, even if the underlying animation data hasn't changed. This means that simply having an AnimationTree running in the editor can cause the scene file to be modified, leading to unintended changes being tracked by version control.

The Impact on Version Control

The consequences of this behavior can be significant. Imagine a project with numerous characters, each with its own AnimationTree. If these AnimationTrees are active in the editor, even minor changes to the scene—such as adjusting a light or repositioning an object—will trigger the saving of bone transformations for all characters. This results in a flood of modifications to the scene files, making it difficult to discern genuine changes from those caused by the AnimationTree activity. The version control history becomes cluttered with commits that primarily reflect the state of the animations in the editor rather than actual design modifications. This “pollution” of the version control history makes it harder to track down specific changes, revert to previous states, and collaborate effectively with a team. Furthermore, the increased size of commits due to these unnecessary changes can impact repository performance and storage.

Reproducing the Issue: A Practical Example

To reproduce this issue, you'll need a Godot project with a character that utilizes an AnimationTree. Here’s a step-by-step guide:

  1. Set up a character with an AnimationTree:
    • Create a new Godot project or use an existing one.
    • Import or create a character model with a skeleton.
    • Create an AnimationTree for the character and set up some basic animations (e.g., idle, walk).
    • Ensure the AnimationTree is active so that the animations play in the editor.
  2. Modify the scene:
    • Make a small, unrelated change to the scene, such as moving a light, adding a new Node, or adjusting a property in the Inspector.
  3. Save the scene:
    • Press Ctrl+S (or Cmd+S on macOS) to save the scene.
  4. Check your version control:
    • Use your Git client (e.g., GitKraken, SourceTree, or the command line) to check the changes in your repository.
    • You will likely see that the scene file associated with your character has been modified, even though you only made a small, unrelated change. Upon inspecting the diff, you'll notice changes in the bone transformation data.

This simple experiment demonstrates how the active AnimationTree causes the scene file to be modified upon saving, leading to version control pollution.

Analyzing the Root Cause

To effectively address this issue, it’s crucial to understand the underlying mechanisms that cause it. The root cause lies in how Godot's editor handles the saving of scene data in conjunction with the real-time updates driven by the AnimationTree. Here’s a breakdown:

  1. Real-time animation updates: When an AnimationTree is active in the editor, it continuously updates the bone transformations of the character's skeleton. This is necessary for previewing animations and posing the character.
  2. Scene saving process: When a scene is saved, Godot serializes the current state of all Nodes and their properties, including the bone transformations of skeletons. This serialization process captures the bone transformations as they exist at the moment of saving.
  3. Unintended modification: Because the AnimationTree is actively modifying the bone transformations, these changes are captured during the saving process, even if they are simply the result of the animation playback and not intentional design changes.

This interplay between real-time animation updates and the scene saving process leads to the unwanted modification of scene files. The bone transformations, which are inherently dynamic due to the AnimationTree, are treated as static data during the save, resulting in the pollution of version control.

Proposed Solutions and Workarounds

Several strategies can be employed to mitigate the version control pollution caused by active AnimationTrees. These solutions range from temporary workarounds to potential long-term fixes within the Godot Engine itself.

1. Deactivate AnimationTrees Before Saving

The most straightforward workaround is to manually deactivate AnimationTrees before saving scenes. This can be done by selecting the character Node and disabling the AnimationTree in the Inspector. While effective, this approach is manual and prone to human error. Developers might forget to deactivate the AnimationTree, leading to unintended changes in the commit history. Despite its limitations, this method provides immediate relief and prevents unnecessary commits.

Pros:

  • Simple to implement.
  • Immediate results.

Cons:

  • Manual and error-prone.
  • Can be time-consuming in large projects.

2. Scripted Automation

To address the manual nature of the previous solution, scripting can be used to automate the deactivation and reactivation of AnimationTrees during the scene saving process. A script can be written to traverse the scene tree, identify AnimationTree Nodes, deactivate them, save the scene, and then reactivate them. This approach reduces the risk of human error and streamlines the workflow. However, it requires some scripting knowledge and adds complexity to the project.

Example GDScript:

# This is a basic example and may need adjustments for your project structure.
func _before_scene_save():
    var animation_trees = get_tree().get_nodes_in_group("animation_trees")
    for tree in animation_trees:
        tree.active = false

func _after_scene_save():
    var animation_trees = get_tree().get_nodes_in_group("animation_trees")
    for tree in animation_trees:
        tree.active = true

Pros:

  • Automates the process, reducing human error.
  • More efficient than manual deactivation.

Cons:

  • Requires scripting knowledge.
  • Adds complexity to the project.
  • Might have performance implications in large scenes.

3. Ignoring Bone Transformation Changes in Git

Another approach is to configure Git to ignore changes in bone transformation data within scene files. This can be achieved by adding patterns to the .gitignore file that exclude specific sections of the scene files containing bone transformation data. While this prevents these changes from being tracked, it also means that legitimate changes to bone transformations might be overlooked. This method should be used with caution and is best suited for projects where bone transformations are rarely modified directly.

Example .gitignore entry:

*.tscn
!/path/to/your/scene.tscn
/path/to/your/scene.tscn:**/skeleton/bones:**

Pros:

  • Prevents pollution of the commit history.
  • Relatively simple to implement.

Cons:

  • May mask legitimate changes to bone transformations.
  • Requires careful configuration to avoid unintended consequences.

4. Feature Request: Delay Bone Transformation Saving

A more robust solution would involve changes within the Godot Engine itself. One approach is to implement a mechanism that delays the saving of bone transformations until the editor is idle or a specific time has elapsed since the last AnimationTree update. This would allow the transformations to settle into a stable state before being serialized, reducing the likelihood of capturing transient changes. This feature could be implemented as a project setting or a per-AnimationTree option.

Pros:

  • Addresses the root cause of the issue.
  • Provides a more seamless workflow.

Cons:

  • Requires changes to the Godot Engine.
  • May introduce new complexities or performance considerations.

5. Feature Request: Resetting Animations on Save

Another potential solution within Godot is to automatically reset animations to their initial state before saving a scene. This would ensure that the saved bone transformations reflect the base pose of the character rather than the current pose driven by the AnimationTree. This approach would require modifying the scene saving process to temporarily pause AnimationTrees, reset the animations, save the scene, and then restore the AnimationTree state. This could be implemented as a global editor setting or a per-scene option.

Pros:

  • Ensures consistent bone transformations in saved scenes.
  • Addresses the root cause of the issue.

Cons:

  • Requires changes to the Godot Engine.
  • May introduce a slight delay during scene saving.

Community Discussion and Solutions

The Godot community has actively discussed this issue, and various solutions and workarounds have been proposed. Some developers have suggested using editor plugins to automate the deactivation and reactivation of AnimationTrees. Others have explored modifying the Godot Engine source code to implement custom scene saving behavior. These community efforts highlight the importance of this issue and the desire for a more robust solution.

Conclusion

The version control pollution caused by saving bone transforms with active AnimationTrees is a significant challenge for Godot developers. Understanding the root cause of the issue is crucial for implementing effective solutions. While workarounds such as manual deactivation and scripting can provide immediate relief, long-term solutions require changes within the Godot Engine itself. Feature requests for delayed bone transformation saving and animation resetting on save offer promising avenues for addressing this problem. By implementing these solutions, Godot can provide a more seamless and efficient workflow for developers using AnimationTrees, ensuring a cleaner and more manageable version control history. The ongoing discussion within the Godot community underscores the importance of this issue, and continued collaboration will be key to finding the best solutions for all developers.