MultiMeshInstance3D in Godot – Complete Guide

Creating visually stunning and performance-efficient games can be quite the balancing act, especially when dealing with numerous similar objects in a 3D environment. Fortunately, there’s a solution within the Godot Engine that makes this task not only possible but surprisingly easy: the MultiMeshInstance3D! In this tutorial, we’ll dive into the world of MultiMeshInstance3D in Godot 4, exploring its capabilities, uses, and benefits. So, gear up to optimize your game’s performance while maintaining its visual fidelity as we take a deep dive into this powerful feature.

What Is a MultiMeshInstance3D?

MultiMeshInstance3D is a vital class in Godot 4 that enables you to instance a MultiMesh resource across your game’s world. In essence, it’s a way to efficiently draw a large number of similar objects, like flora in a forest or a flock of birds, without the performance hit you’d expect from rendering each object individually. It’s a powerful optimization tool that, when used correctly, can help create rich, dynamic environments.

What is it for?

The primary purpose of the MultiMeshInstance3D node is to manage memory and processing resources more effectively. By sharing mesh data between instances, you can populate vast spaces with complex objects without overloading your game’s rendering budget. Whether it’s grains of sand on a beach or stars in a night sky, MultiMeshInstance3D lays the groundwork for you to build these detailed scenes.

Why Should I Learn It?

Understanding and utilizing MultiMeshInstance3D is crucial for any developer looking to create expansive 3D games that run smoothly on a variety of platforms. Knowing how to implement and leverage the power of this class will allow you to:

– Build detailed environments with thousands of objects.
– Manage game performance and optimize rendering times.
– Enhance the overall aesthetics of your game without compromising on quality.

Learning how to use MultiMeshInstance3D effectively will open up new possibilities for your game development projects, ensuring they can handle the complexity that modern games demand. Let’s jump into how you can start utilizing this feature in your own projects with some exciting code examples!

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Setting Up Your MultiMeshInstance3D

Before we jump into the actual code, let’s ensure that you’ve got the basics of setting up a MultiMeshInstance3D in Godot 4. Here’s a step by step guide to get you started:

Step 1: Create a New MultiMesh
First, you’ll want to create a new MultiMesh resource. This resource will hold the data for the mesh we want to instance:

var multi_mesh = MultiMesh.new()

Step 2: Set Mesh and Transform Format
Next, you’ll need to set the mesh that the MultiMesh will use, along with the Transform Format, which specifies how the engine should store each instance’s transform data. The transform includes the position, rotation, and scale:

multi_mesh.transform_format = MultiMesh.TRANSFORM_3D
multi_mesh.mesh = preload("res://path_to_your_mesh.tres")

Step 3: Define Instance Count
Decide and set the amount of instances you’re going to draw. This will allocate the necessary space:

multi_mesh.instance_count = 1000  # Change the number based on how many instances you need

Step 4: Creating a MultiMeshInstance3D
Create a new instance of MultiMeshInstance3D in your world and link it with your MultiMesh resource:

var multi_mesh_instance = MultiMeshInstance3D.new()
multi_mesh_instance.multimesh = multi_mesh
add_child(multi_mesh_instance)

Populating the MultiMesh with Instances

Now that your MultiMeshInstance3D is set up, it’s time to populate it with instances. Each instance can have its own transform (position, rotation, and scale), which you can set with a Transform3D:

Step 1: Create Multiple Transforms
Create a loop to populate your MultiMeshInstance3D with instances at varying positions:

for i in range(multi_mesh.instance_count):
    var transform = Transform3D()
    # Randomly position each instance within a given range
    transform.origin = Vector3(rand_range(-10, 10), rand_range(-10, 10), rand_range(-10, 10))
    
    # Add each transform to the MultiMesh
    multi_mesh.set_instance_transform(i, transform)

Remember to call randomize() early in your script if you want different results each time:

randomize()

Step 2: Customize Transform for Each Instance
You can further customize each instance by scaling and rotating them differently:

for i in range(multi_mesh.instance_count):
    var transform = Transform3D()
    transform.origin = Vector3(rand_range(-10, 10), 0, rand_range(-10, 10))
    
    # Randomly scale and rotate
    transform = transform.scaled(Vector3(randf() + 0.5, randf() + 0.5, randf() + 0.5))
    transform = transform.rotated(Vector3(0,1,0), rand_range(0, 3.14159 * 2))
    
    multi_mesh.set_instance_transform(i, transform)

In the examples above, `rand_range()` gives us a random value in a given range, and `randf()` gives us a random float between 0 and 1. This way, each instance will not only have a unique position but also a unique scale and rotation, adding variety to the scene.

These code snippets form the foundation of using MultiMeshInstance3D in Godot. We have created a MultiMesh, initialized it with the necessary information, and populated it with a multitude of instances. This is just the beginning; in the following part of the tutorial, we will look at how to use materials and colors to further improve your MultiMeshes. Stay tuned!Great! Let’s keep the momentum going and delve into materials and colors, crucial components that bring your MultiMeshInstance3D to life.

Applying Materials to MultiMeshInstance3D

To give your instances a distinct look, you’ll need to apply a material. You can do this by assigning a material to the MultiMesh resource we’ve created:

multi_mesh.mesh.surface_set_material(0, preload("res://path_to_your_material.tres"))

This code assigns a specific material to the surface index of the mesh, effectively altering the appearance of all the instances drawn by our MultiMeshInstance3D.

Coloring Individual Instances

Godot’s MultiMesh also supports per-instance coloring. To leverage this, you must first ensure that the MultiMesh’s color format is set up to support per-instance colors:

multi_mesh.color_format = MultiMesh.COLOR_8BIT  # or COLOR_FLOAT for higher precision

Once that’s done, you can set the color for each instance as follows:

for i in range(multi_mesh.instance_count):
    var color = Color(randf(), randf(), randf(), 1)  # Generate a random color
    multi_mesh.set_instance_color(i, color)

This loop will randomly color each instance, making the scene more vibrant and visually diverse.

Adjusting Instance Visibility

Sometimes you may want to dynamically show or hide specific instances. MultiMesh allows you to set a custom visibility for each instance:

multi_mesh.set_instance_custom_data(0, Vector4(1, 1, 1, 0))  # Hide the first instance
multi_mesh.set_instance_custom_data(1, Vector4(1, 1, 1, 1))  # Show the second instance

The last value in Vector4 correlates to the alpha value. Setting it to 0 will make the instance fully transparent (invisible), while setting it to 1 will fully display the instance.

Handling Large Numbers of Instances

When dealing with vast amounts of instances, you might need to dynamically manage them to keep performance optimized. Here’s an example of how you can add and remove instances on the fly:

// Increasing instance count and adding a new instance
multi_mesh.instance_count += 1
multi_mesh.set_instance_transform(multi_mesh.instance_count - 1, new_transform)

// Decreasing instance count effectively removes the last instance
multi_mesh.instance_count -= 1

If you need to remove an instance that’s not the latest in your series, it’s a good practice to move the last instance to the spot of the one you want to remove and then reduce the instance count:

func remove_instance(index:int):
    if index < multi_mesh.instance_count - 1:
        var last_instance_transform = multi_mesh.get_instance_transform(multi_mesh.instance_count - 1)
        multi_mesh.set_instance_transform(index, last_instance_transform)
    multi_mesh.instance_count -= 1

Remember that altering the instance count dynamically can be costly if done per frame, so it’s best used sparingly.

By incorporating these materials and adjustments, your MultiMeshInstance3D will push your Godot projects to new heights, setting the stage for expansive environments that would have previously been impossible to render efficiently. Whether you’re chasing realism or harnessing stylistic visuals, mastering the use of MultiMeshInstance3D is an essential skill to take your Godot 4 creations to the next level. With these techniques, you’re not just making your games look better—you’re ensuring they perform better too. So go ahead, experiment with these tools, and see where your creativity takes you!Building upon what we’ve discussed, let’s dive deeper into more advanced features that you can leverage with MultiMeshInstance3D, using practical code examples to guide you.

Animating Instances

Imagine you have a field of grass swaying in the wind. You can animate the individual instances to enhance the realism of your scenes. Here’s how you might apply a simple sway animation to each instance:

func _process(delta):
   for i in range(multi_mesh.instance_count):
       var transform = multi_mesh.get_instance_transform(i)
       var original_y = transform.origin.y
       # Apply a sine wave function to oscillate the y-axis  
       transform.origin.y += sin(TIME * i) * delta
       multi_mesh.set_instance_transform(i, transform)

Each grass blade represented by an instance would appear to move individually, thanks to the varying factor `i` in the sine function.

Batching Updates to Improve Performance

When you’re animating or otherwise updating a large number of instances, it’s important to perform operations in batches to minimize the performance hit. You can organize updates so that not all instances are updated every frame:

var batch_size = 100  # Number of instances to update per frame

func _process(delta):
    var frame = Engine.get_frames_drawn() % (multi_mesh.instance_count / batch_size)
    for i in range(frame * batch_size, (frame + 1) * batch_size):
        if i < multi_mesh.instance_count:
            # Your update logic here
            pass

Utilizing Visibility Notifications

Godot provides visibility notifications that you can use to efficiently manage instances. For example, you might only want to animate instances when they are actually visible to the player:

func _notification(what):
    if what == NOTIFICATION_VISIBILITY_CHANGED:
        if is_visible_in_tree():
            set_process(true)
        else:
            set_process(false)

This ensures that your processing logic only runs when necessary, conserving resources for other tasks within your game.

Collision Detection with Instanced Areas

You might also need to have collision detection for your instances. You can achieve this by adding an Area node as a child of your MultiMeshInstance3D:

var area = Area.new()
var shape = SphereShape.new()  # Just an example, use any shape you need
var collision_shape = CollisionShape.new()
collision_shape.shape = shape
area.add_child(collision_shape)
multi_mesh_instance.add_child(area)

Then, you can detect collisions by connecting the Area’s signals to your script.

Custom Shaders on MultiMesh Resources

For even more control over the appearance of your instances, you can use custom shaders. Here’s how you might set up a shader material for your MultiMesh instance:

var shader_material = ShaderMaterial.new()
shader_material.shader = preload("res://path_to_your_shader.shader")
multi_mesh.mesh.surface_set_material(0, shader_material)

With a custom shader, you have the ability to manipulate the appearance at a granular level, such as applying unique effects to each instance based on its position or custom data.

Conclusion

As you can see, MultiMeshInstance3D offers a bevy of opportunities to flex creative muscles and optimize performance. Whether you’re dealing with thousands of grass blades, a school of fish, or a starlit sky, this feature in Godot 4 enables you to maintain high performance and visual quality. The key to mastering MultiMeshInstance3D is understanding the flexibility it provides and finding the right balance for your specific game’s needs. By utilizing these techniques and examples, you’ll be well on your way to creating engaging, dynamic, and efficient 3D environments that will captivate your players. Happy coding!

Where to Go Next in Your Game Development Journey

The path to becoming a distinguished game developer is an adventure full of learning and creation. You’ve explored the capabilities of MultiMeshInstance3D in Godot 4 and are now equipped with knowledge that can open doors to new efficiencies and enhancements in your games. But this is just the beginning—there’s so much more to discover and master in the realm of game development with Godot!

To continue honing your skills and expand your expertise, consider diving into our comprehensive Godot Game Development Mini-Degree. This series of curated courses will guide you through a variety of topics, from working with 2D and 3D assets to mastering gameplay mechanics for a range of game genres. No matter where you are on your journey, from beginner to experienced developer, our Mini-Degree will enrich your toolkit and help you build amazing games.

And for those who wish to explore even further, our broader collection of Godot courses at Zenva offers extensive learning opportunities in this powerful and flexible engine. With our courses, you have the freedom to learn at your own pace and earn certificates that can aid in your career progression or serve as a stepping stone to launching your own game development venture. Keep learning, keep creating, and let Zenva be your guide to achieving game development success.

Conclusion

Embarking on the journey of mastering MultiMeshInstance3D in Godot 4 is just the beginning of what can be an incredibly rewarding venture into game development. With the techniques and insights you’ve gained here, you’re well-equipped to take on more complex projects, optimize your games for performance, and ultimately, bring your most ambitious game ideas to life. Remember, every skill learned and obstacle overcome is a step forward in your path to becoming a seasoned game developer.

We at Zenva are committed to supporting that journey with our Godot Game Development Mini-Degree. Tailored to developers of all levels, this resource is your next stepping stone towards mastery, packed with tutorials, real-world projects, and expert instruction. So, continue to build, create, and grow with us—your next game development breakthrough awaits!

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