Fixing Point Entity Model Rotation Discrepancies Between Trenchbroom And Godot

Introduction

When working with game development, especially level design, the alignment of assets between the level editor and the game engine is crucial. This article addresses a specific issue encountered when using Trenchbroom, a popular level editor, with the Godot game engine via the FuncGodot plugin. The problem arises when point entity models, which are assets placed at specific points in the level, exhibit rotation discrepancies between Trenchbroom and the final in-game build. This can lead to significant frustration for level designers as the intended orientation of objects in the editor does not match what is seen in the game. We will delve into the specifics of this issue, explore potential causes, and discuss possible solutions and best practices to ensure consistent asset alignment.

Understanding the Problem

The core issue is that point entity models placed in Trenchbroom do not always maintain their intended rotation when the level is built and run in Godot using the FuncGodot plugin. This inconsistency can manifest in various ways, such as models appearing rotated by 90, 180, or even arbitrary degrees. Such discrepancies can severely impact the visual fidelity and gameplay experience, as objects might not face the correct direction, leading to misaligned textures, incorrect collision behavior, and overall aesthetic issues.

The user reported experiencing this problem with both FuncGodotFGDModelPointClass and FuncGodotFGDPointClass, indicating that the issue is not isolated to a specific entity type. The target_map_editor setting is correctly set to Trenchbroom, suggesting that the configuration is not the primary cause. Additionally, the issue persists regardless of the apply_rotation_on_map_build setting, implying that the rotation transformation during the build process is not functioning as expected.

To illustrate the problem, the user provided two examples. In the first example, a model's orientation differs significantly between Trenchbroom and Godot. In Trenchbroom, the model faces one direction, but in Godot, it appears rotated. The second example involves a white cube model, where the intended orientation (facing +X in Godot's editor) does not translate correctly to the game environment. This inconsistency suggests that there may be a fundamental mismatch in how rotations are interpreted or applied between the two systems.

Possible Causes for Rotation Discrepancies

Several factors could contribute to the observed rotation discrepancies between Trenchbroom and Godot. These include:

1. Coordinate System Differences

One of the most common causes of rotation issues in game development is the difference in coordinate systems between various tools and engines. Trenchbroom and Godot might use different conventions for defining axes (X, Y, Z) and their directions. For instance, one might use a left-handed coordinate system while the other uses a right-handed system. This difference can lead to rotations being interpreted differently, resulting in misaligned objects.

2. Rotation Order and Conventions

Even if the coordinate systems are aligned, the order in which rotations are applied (e.g., XYZ, ZYX) can significantly affect the final orientation. Additionally, different systems may use different conventions for representing rotations, such as Euler angles, quaternions, or rotation matrices. If Trenchbroom and Godot use different rotation conventions or orders, the same rotation values can produce different results.

3. FuncGodot Plugin Behavior

The FuncGodot plugin itself could be a source of the problem. If the plugin does not correctly handle the conversion of rotation data from Trenchbroom's format to Godot's format, discrepancies can occur. This might involve issues in the plugin's code that incorrectly interpret or transform rotation values during the level import or build process.

4. Model Orientation in Godot

The initial orientation of the model in Godot's editor can also play a role. If the model is not aligned with the world axes in a consistent manner, rotations applied in Trenchbroom might not translate as expected. For example, if a model is designed to face +X in Godot but is imported with a different initial rotation, it could lead to misalignments when placed in the level editor.

5. Incorrect FGD Configuration

The FGD (Forge Game Data) file defines the entities that can be placed in Trenchbroom. If the FGD file is not correctly configured, it could lead to incorrect rotation information being passed from Trenchbroom to Godot. This might involve errors in the entity definitions, such as incorrect default rotations or scaling factors.

6. Build Process Transformations

Transformations applied during the build process can also contribute to rotation issues. If the build process includes steps that modify the rotation of entities, it could lead to discrepancies between the editor view and the final game. This is especially relevant if the apply_rotation_on_map_build setting is not functioning as expected.

Troubleshooting and Solutions

To address the issue of point entity models rotating differently in Trenchbroom and Godot, several troubleshooting steps and solutions can be considered:

1. Verify Coordinate Systems

First, it's essential to verify the coordinate systems used by Trenchbroom and Godot. Determine which axes represent up, forward, and right in each system. If there are differences, adjustments will need to be made to ensure consistent interpretation of rotations.

2. Investigate Rotation Order and Conventions

Next, investigate the rotation order and conventions used by both tools. Determine whether they use the same order for applying rotations (e.g., XYZ) and whether they use Euler angles, quaternions, or rotation matrices. If there are differences, it might be necessary to convert rotation values between the formats.

3. Examine FuncGodot Plugin Code

If the issue seems to stem from the FuncGodot plugin, examine the plugin's code to identify any potential issues in how rotations are handled. Look for sections of code that convert or transform rotation data and ensure that they are correctly interpreting the values from Trenchbroom and applying them to Godot.

4. Ensure Consistent Model Orientation

Make sure that models are oriented consistently in Godot's editor. Ideally, models should be aligned with the world axes, with their forward direction corresponding to a known axis (e.g., +X). This can help minimize rotation discrepancies when placing models in Trenchbroom.

5. Review FGD Configuration

Carefully review the FGD file to ensure that entity definitions are correct. Check for any errors in default rotations, scaling factors, or other properties that might affect the orientation of entities. Ensure that the FGD file accurately reflects the intended behavior of the entities.

6. Test Build Process Transformations

If the build process involves transformations, test these transformations to ensure that they are not causing rotation issues. Temporarily disable or modify the transformations to see if the problem is resolved. This can help isolate the source of the discrepancy.

7. Debugging Techniques

Employ debugging techniques to gain insights into the rotation values at various stages of the process. Print rotation values in Trenchbroom, the FuncGodot plugin, and Godot's editor to compare them and identify where the discrepancies occur. This can help pinpoint the exact cause of the issue.

8. Community Resources and Documentation

Consult community resources and documentation for both Trenchbroom and FuncGodot. Other users might have encountered similar issues and found solutions. Online forums, tutorials, and documentation can provide valuable insights and guidance.

Best Practices for Consistent Asset Alignment

To minimize the risk of rotation discrepancies and ensure consistent asset alignment between Trenchbroom and Godot, consider the following best practices:

1. Establish a Consistent Coordinate System

Establish a consistent coordinate system across all tools and engines used in the development pipeline. This might involve choosing a specific convention (e.g., right-handed) and ensuring that all tools are configured to use it.

2. Define Rotation Conventions

Define rotation conventions and stick to them consistently. Choose a rotation order (e.g., XYZ) and a representation method (e.g., Euler angles or quaternions) and ensure that all tools use the same conventions.

3. Standardize Model Orientation

Standardize model orientation by aligning models with the world axes in Godot's editor. Ensure that the forward direction of models corresponds to a known axis, such as +X or +Z.

4. Document Entity Definitions

Document entity definitions in the FGD file clearly and accurately. Include information about default rotations, scaling factors, and other properties that might affect the orientation of entities.

5. Test Transformations Thoroughly

Test transformations applied during the build process thoroughly. Ensure that transformations are applied correctly and do not introduce unintended rotation changes.

6. Use Version Control

Use version control to track changes to models, levels, and configurations. This can help identify when and where rotation issues were introduced, making it easier to revert to a working state.

7. Collaborate and Communicate

Collaborate and communicate with other developers and level designers. Share knowledge and experiences to help identify and resolve rotation issues more effectively.

Conclusion

Rotation discrepancies between Trenchbroom and Godot, when using the FuncGodot plugin, can be a significant challenge for level designers. By understanding the potential causes of these discrepancies, such as coordinate system differences, rotation order, plugin behavior, model orientation, and build process transformations, developers can take proactive steps to address the issues. Through careful troubleshooting, consistent practices, and community collaboration, it is possible to achieve reliable asset alignment and create immersive and visually consistent game environments. Remember to always verify your coordinate systems, investigate rotation order, and ensure your FuncGodot plugin is correctly configured. By standardizing your workflow and model orientations, you can mitigate many common issues and streamline your level design process. Consistent asset alignment is key to a polished final product, so investing time in understanding and resolving these rotation challenges is a worthwhile endeavor.