UdonSharp Interact vs Input Events: Handling Player Input

You've got a Cube that changes color when pressed. But VRChat has several ways to press.

A controller trigger in VR, a left click on desktop. And you can also receive "the moment they jumped" or "how far the movement key is pushed." Similar names line up and it's unclear which to use.

This article separates action on a target (Interact) from the input itself (Input Events), and confirms it with logs.

What You'll Learn

• The difference between Interact and InputUse
• The three conditions Interact needs to fire
• How to change the usable distance
• That the same events arrive from VR and desktop

Start from having tried your first UdonSharp.

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"Action on a target" and "the input itself"

They look similar and their entry points are completely different.

• Interact is the notification "this object was used." It fires only when the object is in front of you and within reach
• Input Events are the notification "a button was pressed." They fire on that player's PC regardless of what they're looking at

Put plainly, InputUse is "the Use button was pressed" and Interact is "the Use button successfully acted on that Cube." Press with no target and Interact doesn't fire.

The main Input Events:

Event	What it receives
InputUse	Press and release of the use action
InputJump	Press and release of jump
InputGrab / InputDrop	Grab and drop
InputMoveHorizontal / InputMoveVertical	Movement magnitude (-1 to 1)
InputLookHorizontal / InputLookVertical	Amount of look rotation

Button events receive a bool (pressed or released); axis events receive a float (how much).

Input Events fire only on the PC of the person who pressed. To tell others, send the result with the synchronization mechanism.

Hands-On: Tell the two entry points apart with logs

Receive both Interact and Input Events on the same Cube and see the difference in the Console.

1. Place a Cube

Create a "3D Object → Cube," name it InputTestCube, and put it at (0, 1, 1). Leave the Box Collider as is and Is Trigger off.

2. Write code that receives both

In Assets/Scripts, choose "Create → U# Script" and make InputWatcher.

using UdonSharp;
using UnityEngine;
using VRC.Udon.Common;

[UdonBehaviourSyncMode(BehaviourSyncMode.None)]
public class InputWatcher : UdonSharpBehaviour
{
    // Fires only when this object is used
    public override void Interact()
    {
        Debug.Log("[InputWatcher] Interact: this Cube was used");
    }

    // Press and release of Use. Fires whatever you're looking at
    public override void InputUse(bool value, UdonInputEventArgs args)
    {
        Debug.Log("[InputWatcher] InputUse: " + (value ? "pressed" : "released"));
    }

    // Press and release of jump
    public override void InputJump(bool value, UdonInputEventArgs args)
    {
        if (value)
        {
            Debug.Log("[InputWatcher] InputJump: jumped");
        }
    }
}

Don't forget using VRC.Udon.Common;. It's required to use UdonInputEventArgs.

Add a Udon Behaviour to the Cube and set Program Source to InputWatcher. Set Interaction Text to Inspect.

3. Confirm the difference

Press Play, click the Game view, and operate while watching the Console.

Action	Logs produced
Left-click facing nothing, away from the Cube	InputUse: pressed and InputUse: released only
Aim at the Cube and left-click	InputUse: pressed plus Interact
Jump with the space key	InputJump: jumped
Left-click from 10m away from the Cube	InputUse only. No Interact

The difference between the first and second rows is the point of this article. Same button, same person pressing. The only difference is whether it reached a target.

InputUse fires twice: on press and on release. value is true for press and false for release. Logic like "move something only while held" is built from those two.

Three conditions Interact needs

When Interact doesn't fire, it's almost always one of these three.

1. A Collider on the same object: A setup with the program on an empty parent and the Collider on a child Cube won't work
2. Being within reach: The default is around 2m. Too far and nothing appears even when you aim
3. A clear line of sight: Another Collider in front takes priority

To change the distance, raise Proximity on the Udon Behaviour. Making it pressable from far away also increases accidental presses in passing. Keep it to the range you need.

Interaction Text is the prompt shown when you aim at it. Interact works when it's empty too; you just get default text. Use short wording that says what will happen.

Note that a Rigidbody isn't needed. Interact requires only a Collider and a program.

VR versus desktop

The same event names arrive from either environment. Udon absorbs that difference.

The bindings and the nature of the values differ, though.

	Desktop	VR
Use	Left click	Trigger
Jump	Space	A controller button
Movement values	Mostly -1 / 0 / 1	Continuous, by stick deflection

That difference matters when you use the movement axes. Desktop is close to a two-way pressed-or-not, while VR sends intermediate values.

Another important point: input events don't arrive while the menu is open. And the moment the menu opens, a held button is treated as released. Logic that assumes a held button gets cut off here.

When building a "moves only while held" mechanism, writing it so that release always stops it is the safe approach.

Bonus: Good to Know Up Front

• args carries left/right information: Which hand in VR, keyboard or mouse on desktop. Useful when you want different behavior per side
• Input Events run on everyone's PC: They only reach the person who pressed, so telling others requires synchronization. Covered in networking basics
• Interact can be disabled: Turning on DisableInteractive on the Udon Behaviour keeps the program running while refusing interaction. Useful for buttons that are conditionally pressable
• Don't combine it with VRC Pickup: Grabbing takes priority and Interact stops working
• Don't do heavy work in the movement axes: InputMoveHorizontal fires repeatedly while you move. Rather than writing heavy logic directly, store the value in a variable and use it when needed

Summary

Input has two entry points.

• Interact means "this object was used." It needs a target, distance, and line of sight
• Input Events mean "a button was pressed." They fire whatever you're looking at
• Input Events reach only the presser's PC. They don't reach other people
• VR and desktop share event names. Only the nature of the values differs

The question to ask when you're unsure where to write something is: "Is this action on a specific object, or the button itself?" The former is Interact, the latter Input Events.

Next, call the same logic from multiple buttons. Go to methods and custom events, or if you want to build out what a press does, toggling with a button is the practical route.