EditorResourcePreview in Godot – Complete Guide

Embracing the power of previews can significantly enhance the game development process, as they provide insights into how assets will appear in the final product without needing to launch the entire game. This is where the `EditorResourcePreview` class in Godot 4 becomes a pivotal ally for developers. This handy class generates thumbnails or other types of previews for your resources or files, ensuring a smoother and more efficient workflow. By mastering `EditorResourcePreview`, creators can visualize their resources within the editor quickly, aiding in better resource management and a streamlined design experience.

Let’s dig into the details of this valuable class and how it can bolster your Godot 4 development skills.

What is EditorResourcePreview?

`EditorResourcePreview` is a class in Godot Engine, specifically tailored for the game development editor. It is part of the integrated toolset provided by Godot to assist developers in creating previews of their game assets like textures, models, or even scenes.

What is it for?

This node’s main purpose is to generate previews for the resources used in your game, such as textures or models. It’s an incredibly useful tool when you want to quickly view assets without inserting them into the game scene or when you need to create an asset library with visual references.

Why Should I Learn It?

Understanding how to use `EditorResourcePreview` is vital for efficient game development in Godot 4. With it, you can:

– Improve your asset management by having a quick and visual reference for your resources.
– Save time by avoiding the need to run the game to see how an asset looks.
– Customize the preview generation which can be tailored to fit specific requirements of your project.

Discovering how to wield the `EditorResourcePreview` effectively can save creators ample time and provide much-needed agility in the iterative process of game design.

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Creating Basic Previews

To start off, let’s create a basic thumbnail for a texture. This can help quickly identify textures in a custom asset manager or inspector.

var preview_generator = EditorResourcePreview.new()

func _ready():
    var texture_path = "res://path_to_your_texture.png"
    var texture = load(texture_path) 
    preview_generator.queue_resource_preview(texture, self, "_thumbnail_ready", texture_path)

func _thumbnail_ready(preview, path, data):
    var texture_preview = preview as Texture
    # You can now use `texture_preview` as a preview of your texture asset

In this code, we create an instance of the `EditorResourcePreview` class. We then load a texture and queue a preview to be generated. The `_thumbnail_ready` callback function is called when the preview is ready.

Generating Previews for 3D Models

Similar to textures, we can also generate previews for 3D models. This is useful to visualize models right inside the editor without placing them into a scene.

func generate_preview_for_mesh(mesh_resource_path):
    var mesh = load(mesh_resource_path)
    var mesh_preview = EditorResourcePreview.new()
    mesh_preview.queue_resource_preview(mesh, self, "_mesh_preview_ready", mesh_resource_path)

func _mesh_preview_ready(preview, path, data):
    var mesh_preview_texture = preview as Texture
    # Here we can display or use the texture preview of the 3D model.

Here, we’re loading the mesh resource just like we did for the texture, and then we use the `queue_resource_preview` method to start generating the preview. Once done, `_mesh_preview_ready` gives us the preview as a `Texture`.

Handling Previews for Multiple Resources

When dealing with multiple resources, managing the callbacks efficiently is crucial. Here’s how you can handle generating previews for a list of textures:

var resource_paths = ["res://texture1.png", "res://texture2.png", "res://texture3.png"]
var previews = {}

func _ready():
    var preview_generator = EditorResourcePreview.new()
    for path in resource_paths:
        var resource = load(path)
        previews[path] = null
        preview_generator.queue_resource_preview(resource, self, "_resource_preview_ready", path)

func _resource_preview_ready(preview, path, data):
    previews[path] = preview
    # Now `previews` dictionary holds the path and their respective previews.

This script loads multiple resources and queues them for preview generation. Each callback associates the preview with the resource path in the `previews` dictionary.

Updating Previews in Real-Time

Suppose you have an inspector or a custom UI where you want to display these previews. You would need to update them in real-time as they become ready. Here’s an approach to update a preview in an `TextureRect` as soon as it’s available:

func generate_and_display_preview(texture_path, preview_area):
    var texture = load(texture_path)
    var preview_generator = EditorResourcePreview.new()
    preview_generator.queue_resource_preview(texture, self, "_update_texture_rect", preview_area)

func _update_texture_rect(preview, path, preview_area):
    if preview:
        preview_area.texture = preview
    else:
        print("Failed to generate preview for the path: ", path)

This method involves passing the UI element as the `data` parameter (in this case, `preview_area`), which is a `TextureRect`, and then assigning the generated texture directly to it in the `_update_texture_rect` callback.

These examples should give you a solid foundation for generating and using resource previews within the Godot 4 editor. In the next part, we will explore more advanced uses of the `EditorResourcePreview` class.

Advanced Preview Customization

Sometimes, the default previews may not be enough for your needs. You might want to customize how these previews are generated. For example, if you have a custom resource type, you can specify different preview logic.

class CustomResourcePreviewGenerator extends EditorResourcePreviewGenerator:

    func can_generate_small_preview(resource):
        return resource is MyCustomResource

    func generate(resource, size, preview, for_editor):
        var custom_preview_image = ImageTexture.new()
        # Custom logic to generate preview from `MyCustomResource`
        # set the preview image with the generated preview
        return custom_preview_image

func _ready():
    var custom_generator = CustomResourcePreviewGenerator.new()
    EditorResourcePreview.add_preview_generator(custom_generator)

In this snippet, we extend `EditorResourcePreviewGenerator` to create a new generator that can handle our `MyCustomResource`. Then, we override `can_generate_small_preview` and `generate` where we define how the preview is created.

Preview Generation for Script Resources

Even for scripts, you might want to generate a specific preview to represent the functionality or category they belong to. Here’s how you might go about that:

func generate_script_preview(script_path):
    var script_resource = load(script_path)
    var preview_gen = EditorResourcePreview.new()

    preview_gen.queue_resource_preview(script_resource, self, "_script_preview_ready", script_path)

func _script_preview_ready(preview, path, data):
    if preview:
        process_script_preview(preview, path)
    else:
        print("Failed to generate preview for script at: ", path)

func process_script_preview(preview, path):
    # Do something with the script preview

In this example, we load a script and queue it for preview generation much like any other resource.

Dynamic Preview Updates for Edited Resources

When a resource is edited, its preview may need an update. You can listen for changes and regenerate previews dynamically:

func _ready():
    var texture_path = "res://icon.png"
    var texture = load(texture_path)
    var preview_gen = EditorResourcePreview.new()
    preview_gen.connect("preview_invalidated", self, "_regenerate_preview")

    # Generate initial preview
    preview_gen.queue_resource_preview(texture, self, "_thumbnail_ready", texture_path)

func _regenerate_preview(path):
    if path == "res://icon.png":
        print("Icon texture preview invalidated, regenerating...")
        generate_preview_for_path(path)

func generate_preview_for_path(path):
    var resource = load(path)
    var preview_gen = EditorResourcePreview.new()
    preview_gen.queue_resource_preview(resource, self, "_thumbnail_ready", path)

Here, you can connect to the `preview_invalidated` signal to detect when a resource has changed and regenerate its preview. This keeps the thumbnails updated when assets are modified.

Creating Previews for Collections of Resources

If you have a collection of resources, such as a set of characters or items, you may want to generate and display previews for them in a grid or list:

func generate_previews_for_collection(resources):
    var preview_gen = EditorResourcePreview.new()
    for resource in resources:
        var res = load(resource)
        preview_gen.queue_resource_preview(res, self, "_collection_preview_ready", resource)

func _collection_preview_ready(preview, path, data):
    if preview:
        add_preview_to_collection(preview, path)
    else:
        print("Failed to generate preview for ", path)

func add_preview_to_collection(preview, resource_path):
    # Logic to add the preview to a UI grid or list

With this setup, each resource in the collection will have a preview generated and then added to the user interface, facilitating seamless browsing and selection.

Optimizing Preview Generation

Generating previews can be resource-intensive, especially for large projects. Here’s how you may handle this optimally:

func generate_optimized_previews(resource_paths):
    var preview_gen = EditorResourcePreview.new()
    preview_gen.connect("preview_ready", self, "_on_preview_ready")
    for path in resource_paths:
        var res = load(path)
        preview_gen.queue_resource_preview(res, self, "_on_preview_ready", path)

func _on_preview_ready(preview, path, data):
    if preview:
        store_preview_in_cache(path, preview)
    else:
        print("Failed to generate preview for ", path)

func store_preview_in_cache(path, preview):
    # Store the preview in a cache system to avoid regenerating needlessly
    # This could be a dictionary or a more complex cache system

By connecting once to the `preview_ready` signal and storing the generated previews in a cache system, you reduce the workload for the engine and ensure quicker access when the same previews are needed again. This example outlines how to load and use `EditorResourcePreview` with attention to performance, avoiding unnecessary regeneration of previews.

Feel free to use these scripts as starting points for implementing the `EditorResourcePreview` in your own Godot projects. By leveraging this functionality, you’re bound to see a boost in your development workflow, and with practice, you’ll find even more creative ways to use previews throughout your game development process.Now let’s dive deeper into the capabilities of the `EditorResourcePreview` class with more examples that cater to different use cases and scenarios. Here, we’ll explore advanced integration into the Godot editor, customization of previews for better resource management, and performance considerations when generating previews for large sets of assets.

Generating Animated Texture Previews

If you’re using animated textures in your project, displaying a static preview might not be enough. To better represent these resources, you may want to generate an animated preview:

func generate_animated_texture_preview(animated_texture_path):
    var animated_texture = load(animated_texture_path)
    var preview_gen = EditorResourcePreview.new()
    preview_gen.queue_resource_preview(animated_texture, self, "_animated_texture_preview_ready", animated_texture_path)

func _animated_texture_preview_ready(preview, path, data):
    if preview:
        display_animated_texture_preview(preview)
    else:
        print("Failed to generate preview for animated texture at: ", path)

func display_animated_texture_preview(animated_preview):
    # Logic to display the animated texture preview in your custom editor plugin or UI

Custom Preview for Imported Assets

In the case of imported assets, such as 3D models or animations, you might need to gather additional data to generate a more informative preview:

func generate_imported_asset_preview(imported_asset_path):
    var imported_asset = load(imported_asset_path)
    var preview_gen = EditorResourcePreview.new()
    preview_gen.queue_resource_preview(imported_asset, self, "_imported_asset_preview_ready", imported_asset_path)

func _imported_asset_preview_ready(preview, path, data):
    if preview:
        # Optionally, extract more data from the imported asset if necessary
        var additional_info = extract_info_from_imported_asset(imported_asset)
        show_imported_preview_with_details(preview, additional_info)
    else:
        print("Failed to generate preview for imported asset at: ", path)

func extract_info_from_imported_asset(asset):
    # Extracts metadata or additional details for imported assets
    return asset.get_import_metadata()

func show_imported_preview_with_details(preview, additional_info):
    # Shows the preview alongside extra details in your custom UI

Generating Previews for Script Files

Let’s say you want previews for your scripts to quickly identify different types (eg. NPC scripts, item scripts, etc.):

func generate_previews_for_scripts(scripts):
    var preview_gen = EditorResourcePreview.new()
    
    for script in scripts:
        var script_resource = ResourceLoader.load(script)
        if script_resource:
            preview_gen.queue_resource_preview(script_resource, self, "_script_preview_ready", script)

func _script_preview_ready(preview, script, data):
    if preview:
        add_script_icon(preview, script)
    else:
        print("Failed to generate preview for script: ", script)
    
func add_script_icon(preview, script):
    # Here you could add an icon to each script in the editor, for example
    var script_icon = preview as Texture
    # Apply the `script_icon` to your script resource or UI

Previews for Shaders

You can extend the preview functionality to shaders by rendering a mesh with the shader applied to it and creating a preview from that:

func generate_shader_preview(shader_path, mesh):
    var material = ShaderMaterial.new()
    material.shader = load(shader_path)
    
    var preview_gen = EditorResourcePreview.new()
    preview_gen.queue_resource_preview(material, self, "_shader_preview_ready", shader_path)

func _shader_preview_ready(preview, path, data):
    if preview:
        display_shader_preview(preview)
    else:
        print("Failed to generate preview for shader at: ", path)

func display_shader_preview(shader_preview):
    # Logic to display the shader preview in your custom editor plugin or UI
    # For instance, setting this preview as a thumbnail for a shader list

Batch Preview Generation for Project Assets

In large projects, you may want to generate previews for all project assets for better navigation and management:

func generate_previews_for_project_assets(asset_paths):
    var preview_gen = EditorResourcePreview.new()
    for path in asset_paths:
        var asset = load(path)
        preview_gen.queue_resource_preview(asset, self, "_project_asset_preview_ready", path)

func _project_asset_preview_ready(preview, path, data):
    if preview:
        store_preview_in_project_asset_database(path, preview)
    else:
        print("Failed to generate preview for project asset at: ", path)

func store_preview_in_project_asset_database(path, preview):
    # Storing the preview in a central database or cache, possibly indexed by the asset path

Remember, when generating a large number of previews, consider using background threads or processing them over multiple frames to avoid locking up the editor.

Performance Optimization for Real-Time Preview Updates

Updating the previews in real-time as the assets change can be performance-intensive. Off-loading this task to a background thread can help maintain editor responsiveness:

func generate_preview_async(resource_path):
    var resource = load(resource_path)
    var preview_thread = Thread.new()
    preview_thread.start(self, "_generate_preview_background", resource)

func _generate_preview_background(resource):
    # This is run in a background thread
    var preview_gen = EditorResourcePreview.new()
    var preview = preview_gen.generate_small_preview_for_resource(resource)
    call_deferred("_apply_preview", resource, preview)

func _apply_preview(resource, preview):
    # Apply the generated preview in the main thread to avoid threading issues

Utilizing the `Thread` class allows resource-intensive tasks, such as generating previews for complex resources, to run without interrupting main thread operations like the editor interface or game simulation.

Managing previews effectively can significantly speed up the development process, helping you and your team to keep things organized and user-friendly. The `EditorResourcePreview` class is just one of the many sophisticated tools that Godot provides, and with it, you can truly customize your development experience to suit your project’s needs.

Continuing Your Journey in Game Development

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Conclusion

Delving into the capabilities of Godot 4’s `EditorResourcePreview` class reveals just a glimpse of the remarkable opportunities available in game development. It’s tools like these that allow us to weave creativity with technology, shaping our ideas into tangible, interactive experiences. We hope that this exploration has sparked your enthusiasm and that you’re inspired to apply these concepts in your projects. Remember, your ability to innovate and craft immersive games grows with every new skill you acquire and every challenge you embrace.

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