Unity Tutorial #7: Custom Actions in OpenXR

@Brian Kim (3/14/2023)

Requirements

Installation of Unity

Creating a Custom Action

Unity and OpenXR have built-in support for several actions, including locomotion, teleportation, grabbing objects, and working with buttons. However, if you are trying to include actions that are not in the standard library, it might be difficult to find the relevant documentation.

So, for this tutorial, we'll go over a fairly basic custom interaction in OpenXR. We'll create an object in a Unity Scene, and have the object change color when we click our trigger key. This will require custom actions on the part of a controller and an object, requiring code to be written.

At this point, we want to create a new action mapping to explore how this feature works, so open the "CustomActions" mapping and click on the "+" next to "Action Maps." This will allow us to create our own action mappings, which we can title whatever we want. For now, I'll go with "Custom."

Creating Action Code

Now, close the action mappings window, making sure to save the new changes, and go to the Assets folder. There, create a new subfolder called "Scripts," and in that folder, create a new C# file, which I will name "ToggleExample."

For the file, copy the following code:

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.InputSystem;

public class ToggleExample : MonoBehaviour

{

    public InputActionReference toggleRef = null;

    void Awake()

    {

        toggleRef.action.started += Toggle;

    }

    // Update is called once per frame

    void Update()

    {

        toggleRef.action.started -= Toggle;

    }

    private void Toggle(InputAction.CallbackContext context)

    {

        bool active = !gameObject.activeSelf;

        gameObject.SetActive(active);

    }

}

Next, create a new C# file called "ColorExample" and write the following code:

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.InputSystem;

public class ColorExample : MonoBehaviour

{

    public InputActionReference colorRef = null;

    private MeshRenderer meshRenderer = null;

    void Awake()

    {

        meshRenderer = GetComponent<MeshRenderer>();

    }

    // Update is called once per frame

    void Update()

    {

        float val = colorRef.action.ReadValue<float>();

        UpdateColor(val);

    }

    private void UpdateColor(float val)

    {

        meshRenderer.material.color = new Color(val, val, val);

    }

}

"ToggleExample" will detect input actions from a controller input that is bound to it, and "ColorExample" will update the color of the object that it is attached to.