PlaceholderMesh in Godot – Complete Guide

Welcome to our dive into the world of Godot 4 with a focus on the PlaceholderMesh class! Whether you’ve been crafting games for years or you’re right at the start of your journey, understanding the ins and outs of game engines and their components is crucial. Today’s topic is not only fascinating, but it also helps us tackle practical challenges in game development. We’ll explore the purpose and use of PlaceholderMesh, and by the time we’re done, you’ll see how this seemingly minor feature can be a powerhouse in your development toolkit.

What is PlaceholderMesh?

The PlaceholderMesh is a class within the Godot 4 engine that derives from the base Mesh class. When dealing with two specific scenarios in game development—running a project in dedicated server mode and loading a project in a different engine version—the PlaceholderMesh becomes extremely useful.

What is it for?

Let’s imagine you’re working on an epic multiplayer game. You have stunning visuals, but you also need to export a server-only version. This dedicated server doesn’t need the full graphic details, only the texture dimensions for gameplay purposes. Here, PlaceholderMesh steps in to strip down the visuals while keeping those crucial size details. Additionally, it provides a fallback when the usual Mesh subclass isn’t available due to different engine versions or builds.

Why Should I Learn It?

Understanding the PlaceholderMesh class can significantly streamline your game development process. Not only does it aid in reducing the file size of your exported games (particularly important for server-only versions), but it also ensures that your project remains flexible and functional across different versions of Godot. By mastering this class, you position yourself to manage resources wisely, optimize performance, and maintain project integrity. Now, let’s dive deeper into how PlaceholderMesh works through hands-on coding examples.

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Creating a PlaceholderMesh in Godot 4

To create a PlaceholderMesh in Godot 4, you first need to understand how to define a Mesh instance in the engine. This setup is fundamental as PlaceholderMesh inherits from Mesh. We’ll start by setting up a simple Mesh instance before converting it to a PlaceholderMesh.

var mesh = Mesh.new()

Now let’s assume you have a Mesh instance for a 3D model in your game, and you would like to replace it with a PlaceholderMesh.

var placeholder_mesh = PlaceholderMesh.new()
placeholder_mesh.create_from_mesh(existing_mesh)

This snippet creates a new PlaceholderMesh from an existing Mesh. The `create_from_mesh` method copies the parameters of the existing Mesh, ensuring your PlaceholderMesh retains the necessary spatial information.

Using PlaceholderMesh in a MeshInstance

MeshInstance is the node used to display 3D meshes in Godot. Here’s how to set a PlaceholderMesh in a MeshInstance node.

# Assume you have a MeshInstance node
var mesh_instance = $MeshInstance

# Assign your PlaceholderMesh to the MeshInstance
mesh_instance.mesh = placeholder_mesh

This code will effectively substitute the visual Mesh with a PlaceholderMesh, reducing the rendering complexity while keeping the transform and bounds intact.

Configuring PlaceholderMesh Parameters

PlaceholderMesh also comes with its own parameters you can adjust. Let’s look at how you can set the size of the PlaceholderMesh to match the intended bounds of your model.

# You can set the size directly if you know the required dimensions
placeholder_mesh.size = Vector3(2.0, 1.0, 1.0)

This code sets the PlaceholderMesh to have a width of 2 units, height of 1 unit, and depth of 1 unit. It’s essential for making sure that space interactions, like collisions and visibility checks, remain accurate.

Scripting Custom Behavior for PlaceholderMesh

Sometimes you might want to script custom behavior for when a PlaceholderMesh is used. For example, consider the case where you want to load a PlaceholderMesh only under certain conditions, such as a server mode or a particular graphical setting. Here is how you might check for server mode and replace meshes accordingly:

# Check if the game is running in server mode
if OS.get_singleton().is_stdout_verbose():
    var mesh_instance = $MeshInstance
    mesh_instance.mesh = placeholder_mesh
    # You can log this change for debug purposes
    print("PlaceholderMesh has been used for server mode.")

This code checks if the game is running in server mode, and if so, replaces the Mesh in your MeshInstance with a PlaceholderMesh. Logging this action can be useful for debugging and verifying your game’s behavior.

Each of these code snippets takes us further into Godot’s capabilities and demonstrates how using PlaceholderMesh can help optimize our projects and maintain functionality across different scenarios. Stay tuned for the next part, where we will delve into more advanced examples and use-cases.Continuing with our exploration of the PlaceholderMesh in Godot 4, let’s examine a few more advanced examples that highlight its powerful applications.

Adding PlaceholderMesh to a Scene on the Fly

Sometimes you want to streamline the scene while the game is running. For instance, you might want to replace all meshes with placeholders when the camera is far away to improve performance. Here’s a code snippet that executes this:

func _on_Camera_distance_threshold_passed():
    for mesh_instance in get_tree().get_nodes_in_group("high_detail_meshes"):
        var placeholder = PlaceholderMesh.new()
        placeholder.create_from_mesh(mesh_instance.mesh)
        mesh_instance.mesh = placeholder

When the camera passes a certain distance threshold, every Mesh in the group “high_detail_meshes” is replaced with a PlaceholderMesh.

Restoring Original Meshes

At some point, you may want to revert back to the original, more detailed meshes, like when the camera gets closer. You’ll need to keep a reference to the original meshes to do this. Here’s how you might approach it:

# Store original mesh references here
var original_meshes = {}

func _ready():
    for mesh_instance in get_tree().get_nodes_in_group("high_detail_meshes"):
        original_meshes[mesh_instance] = mesh_instance.mesh

func _on_Camera_close_enough():
    for mesh_instance in original_meshes.keys():
        mesh_instance.mesh = original_meshes[mesh_instance]

This script stores the original Mesh in a dictionary upon the game’s load. It then restores the meshes when the camera is close enough.

Saving Memory with PlaceholderMesh in Resource-Intensive Scenes

Consider a level with dozens of high-poly models that are not essential for gameplay, like background buildings. Using PlaceholderMeshes for these models can reduce memory usage. Here’s how you can initialize a resource-intensive scene:

func _load_scene_with_placeholders(scene_path):
    var scene = load(scene_path).instance()
    for mesh_instance in scene.get_children():
        if mesh_instance is MeshInstance and needs_placeholder(mesh_instance):
            mesh_instance.mesh = create_placeholder_for(mesh_instance.mesh)
    return scene

func needs_placeholder(mesh_instance):
    return mesh_instance.mesh.get_surface_count() > SOME_POLY_COUNT_THRESHOLD

func create_placeholder_for(original_mesh):
    var placeholder = PlaceholderMesh.new()
    placeholder.create_from_mesh(original_mesh)
    return placeholder

Before the scene is added to the tree, this function replaces heavy MeshInstances with PlaceholderMeshes, keeping the application’s memory footprint lower.

Clever Use of PlaceholderMesh During Level Design

Level designers can use PlaceholderMesh to visualize spaces while designing levels without stressing the graphics card. A mesh with complex shaders might be too heavy to handle in the editor with many instances, but placeholders can keep things running smoothly. Here’s an example of a function a level designer could use to swap in placeholder meshes temporarily while working:

# Helper function for level designers to toggle placeholder meshes in the editor
func _toggle_placeholder_meshes(use_placeholders):
    var meshes = get_tree().get_nodes_in_group("interactive_objects")
    for mesh_instance in meshes:
        if use_placeholders:
            mesh_instance.mesh = create_placeholder_for(mesh_instance.mesh)
        else:
            mesh_instance.mesh = retrieve_original_mesh_for(mesh_instance)

func retrieve_original_mesh_for(mesh_instance):
    # Code to retrieve the original mesh for the instance

This kind of script can be triggered by a key press or editor plugin, allowing level designers to quickly switch between the original meshes and placeholders.

These examples scratch the surface of what’s possible with the PlaceholderMesh class in Godot 4. By exploring these concepts, we show how PlaceholderMesh can be a flexible tool in various development stages, making our game design workflow more efficient and adaptable. Remember, these scripts are just starting points, and we encourage you to modify and expand these examples to fit your project’s specific needs.Certainly! As we continue our exploration of PlaceholderMesh in Godot 4, we will delve into even more practical code examples that can enhance your game development workflow.

When managing a game with multiple levels or scenes, it can be highly beneficial to batch process the replacement of meshes with placeholders to optimize the whole game’s performance in certain scenarios. Here’s a script that can automate this task for all scenes in a project.

# A script to traverse all scenes and replace meshes with placeholders
func batch_replace_meshes_with_placeholders():
    var scenes_to_process = ["res://levels/level1.tscn", "res://levels/level2.tscn", ...]
    
    for scene_path in scenes_to_process:
        var scene_resource = load(scene_path)
        var scene_nodes = scene_resource.get_children()

        for node in scene_nodes:
            if node is MeshInstance:
                var placeholder = PlaceholderMesh.new()
                placeholder.create_from_mesh(node.mesh)
                
                node.mesh = placeholder
                print("Replaced mesh with placeholder in ", node.name)
        
        # Optionally, save the modified scene
        ResourceSaver.save(scene_path, scene_resource)

This function iterates through a predefined list of scene paths, replacing each Mesh with a PlaceholderMesh and then saving the modified scene.

If your game has a level editor or allows players to customize their environment, you might want to give them the option to toggle PlaceholderMeshes. Here is an example of how this can be implemented:

# A player-accessible toggle for PlaceholderMeshes in a custom level editor
func _on_use_placeholders_toggled(is_active):
    for mesh_instance in get_tree().get_nodes_in_group("customizable_objects"):
        if is_active:
            mesh_instance.mesh = create_placeholder_for(mesh_instance.mesh)
        else:
            mesh_instance.mesh = original_meshes[mesh_instance]

This allows players to toggle the placeholders on and off within the editor, potentially improving their experience with lower-spec systems.

For developers who integrate machine learning or AI into their games, ensuring that the game runs at a high performance during training is vital. You can use PlaceholderMesh to simplify the visuals and speed up the training process, as visual details are typically unnecessary for AI. Below is an example of how this can be set up:

# Replace meshes with placeholders during an AI training session
if is_ai_training_mode():
    for mesh_instance in get_tree().get_nodes_in_group("ai_training_objects"):
        var placeholder = PlaceholderMesh.new()
        placeholder.create_from_mesh(mesh_instance.mesh)
        mesh_instance.mesh = placeholder

We’re always optimizing for different hardware profiles, and using PlaceholderMesh allows us to create a low-specification mode easily. Here’s how we might enable this mode for players:

# A simple function to toggle Low-Spec mode using PlaceholderMesh
func enable_low_spec_mode(enable):
    var mesh_instances = get_tree().get_nodes_in_group("dynamic_objects")
    
    for mesh_instance in mesh_instances:
        if enable:
            if "placeholder" in mesh_instance:
                continue  # Skip if already a placeholder
            var placeholder = PlaceholderMesh.new()
            placeholder.size = mesh_instance.mesh.get_aabb().size
            mesh_instance.placeholder = mesh_instance.mesh
            mesh_instance.mesh = placeholder
        elif "placeholder" in mesh_instance:
            mesh_instance.mesh = mesh_instance.placeholder
            mesh_instance.placeholder = null

Lastly, let’s consider a debug tool for developers. A wireframe overlay can be useful to visualize hitboxes or object bounds, and here’s how you can use PlaceholderMesh to create a debug overlay:

# Generate a wireframe overlay using PlaceholderMesh
func generate_wireframe_overlay():
    for mesh_instance in get_tree().get_nodes_in_group("meshes_to_debug"):
        var wireframe_mesh = Mesh.new()
        wireframe_mesh = mesh_instance.mesh.create_outline(0.05)
        mesh_instance.add_child(wireframe_mesh)

By adding these scripts to your Godot project, you are able to take full control over the rendering complexity of your scenes. These examples illustrate that PlaceholderMesh is not only valuable for performance optimization but also for building more dynamic and flexible tools within your game development process.

Continuing Your Game Development Journey with Godot

Exploring the depths of game creation with Godot is an exciting journey, and there’s always more to learn and master. If you’ve enjoyed our exploration of the PlaceholderMesh class and other facets of game development with Godot 4, then we’ve got just the thing to continue your adventure: our Godot Game Development Mini-Degree.

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For those who want to expand their knowledge further, we offer a broader collection of courses that cater to both budding game developers and those looking to deepen their existing expertise. Visit our range of Godot courses and continue your path to becoming a game development pro with Zenva, where learning is flexible, project-based, and accessible on any modern device.

Conclusion

In wrapping up our session on the PlaceholderMesh in Godot 4, we’ve ventured through various scenarios where this powerful feature can transform your game development workflow. Whether it’s optimizing server performance, streamlining level design, or facilitating AI training, understanding and utilizing PlaceholderMesh can lead to more efficient and adaptable games. Remember, the art of game development is a constant learning process, and every tool and technique you master brings you one step closer to realizing your creative vision.

Don’t let the learning stop here! Join us at Zenva, where our Godot Game Development Mini-Degree awaits to unlock new realms of game creation. Equip yourself with knowledge, gain practical skills, and let’s bring those game dreams to life together. Continue to challenge yourself, experiment boldly, and grow with each line of code – your next game-changing project is just a course away!

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