How to Instance an object in Godot?

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So I basically have some fair knowledge of Opengl 4.0. In OpenGL you can render the same object at many places. This is a technique called Instancing. This saves up some CPU calls or something.

I wanted to do this in Godot. So I looked up in the docs and it basically just tells me to duplicate an object. But I think this does not save the CPU calls to the GPU, like how Instancing does (please let me know if I'm wrong about this).

Plus I cannot have all the nodes beforehand. Because the number of times I need to render the object(at different places) is determined during runtime and can change.

Is there a solution to this? Any help would be appreciated.

Thank you

godot game-development rendering
2 Answers

Instancing can be thought of as making copies of an object from a blueprint. The reason it saves memory and draw calls is that essentially, only the "blueprint" must be kept in memory. The recommended way that Godot addresses this (as per the documentation) is through (packed) scenes.

To do this, create the object as it's own scene - remember that you can right click on the root node of a scene (even an empty one) and change the type to whatever you want. Once you have the object set up the way you like, save it as it's own scene (ex: myInstance.tscn).

From there, you can call upon the instance from your main scene (or whatever scene you need it in). To do this you need to do a couple of things:

First, create a variable for your instance in the script you want to call it from by declaring something like onready var instancedObject = preload("res://myInstance.tscn"). (Using whatever path you used for the scene).

From there, you call the variable from whatever function you need by writing something like: var myObject = instancedObject.instance()

You then must add the instance to the current scene with add_child(myObject)

After this, you can (optionally) specify things like transforms and rotations to determine where the instance gets put (Ex: myObject.transform.origin = Vector3(0,10,0) - For 3D, or myObject.position = Vector2(10,0) for 2D)

Alternatively, you can initialize and instance the object at the same time by writing onready var instancedObject = preload(res://myInstance.tscn).instance(), and then adding it in functions by using add_child(instancedObject), however although it requires fewer steps, there are limitations to doing it this way, and I personally have had much more success using the first approach.

If, however, you are looking to instance multiple thousands of objects (or more) in the same scene, I recommend using Calinou's answer and using a MultiMeshInstance. However, one of the limitations of the MultiMeshInstance is that it uses an all or nothing approach to drawing, meaning all instances will either be all drawn at once, or not drawn at all. There is no in-between. This could be good or bad depending on what you need it for.

Hope this helps.

user_113084310

Instancing in Godot is handled using the MultiMeshInstance node. It's the instanced counterpart to MeshInstance. See Optimization using MultiMeshes in the documentation for more information.

Keep in mind MultiMeshes aren't suited if you need to move the objects in different directions every frame (although you can can achieve this by using INSTANCE_ID in a shader shared among all instances). MultiMeshInstance lets you change how many instances are visible by setting its visible_instance_count property.

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