Runtime anchors

Runtime anchors, or simply "anchors", are a way for objects to reference something (another GameObject or Component) which would be impossible to setup in Edit mode. They generally cover two needs:

• Referencing a GameObject or Component which is instantiated at runtime.
• Referencing a GameObject or Component which is in another scene.

As a ScriptableObject, Runtime anchors provide an "anchor" that the designer can point to while setting up a Prefab, so that the object can find that reference later, at runtime, when it's made available.

Using this pattern (and other ScriptableObject-based references), we have Prefabs in the project that can be dropped in a scene and will work automatically, without a need for cross-object connections to be setup. These connections will be made at runtime.

Table of Contents

• Usage example
• More info

Usage example

One of the main uses of this pattern in the project revolves around the player spawning. Since the protagonist is spawned (and respawned) at runtime, we can't set it as a target for Cinemachine in Edit mode.

For this reason, the CameraManager script refers to a TransformAnchor ScriptableObject, knowing that at runtime, at some point, it's going to contain the Transform of the player character. When this happens, we call a function (SetupProtagonistVirtualCamera()) to setup Cinemachine with the correct target.

The function is called in Start, only if the Transform is already available (meaning the protagonist has been already spawned).

private void Start()
{
	//Setup the camera target if the protagonist is already available
	if(_protagonistTransformAnchor.isSet)
		SetupProtagonistVirtualCamera();
}

The CameraManager also subscribes to the Runtime anchor's event, so that it's notified in case the Transform contained in it were to change. This way, whenever the player is respawned, the camera is setup again and frames the correct Transform:

private void OnEnable()
{
	_protagonistTransformAnchor.OnAnchorProvided += SetupProtagonistVirtualCamera;
}

More info

Runtime Anchors are our implementation of a similar concept from other projects with similar needs. In the below resources, they are referred to as "Runtime Sets", and they can contain multiple objects of the same type - while we generally use them for one object.

• Ryan Hipple's original video on ScriptableObjects patterns, Unite Austin 2017 (specific timing for Runtime Sets linked)
• Another video on Runtime Sets, by Matt Schell