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1. What is the PhysicsRaycaster component?

PhysicsRaycaster is a component in Unity UGUI that is used for physical ray detection on UI elements. It can detect whether a mouse or touch event occurs on a UI element and pass the event to the corresponding UI element.

2. The working principle of PhysicsRaycaster

PhysicsRaycaster detects UI elements by emitting a ray. When a ray intersects a UI element, the PhysicsRaycaster delivers the event to the corresponding UI element.

3. Common properties of PhysicsRaycaster

Event Mask: Specify which layers of UI elements can receive events.
Max Raycast Distance: Specifies the maximum detection distance of the ray.
Blocking Objects: Specify which types of objects can block ray detection.

4. Commonly used functions of PhysicsRaycaster

Raycast: emits a ray and returns the UI elements that intersect it.

5. Complete example code

Example 1: Click the button to change the color

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class ButtonColorChanger : MonoBehaviour, IPointerClickHandler
{
    private Image image;

    private void Start()
    {
        image = GetComponent<Image>();
    }

    public void OnPointerClick(PointerEventData eventData)
    {
        image.color = Random.ColorHSV();
    }
}

Steps:

Create a Canvas object and create a Button object under the Canvas.
Set the Color property of the Button object’s Image component to any color.
Set the Event Mask property of the Button object’s PhysicsRaycaster component to its default value.
Attach the ButtonColorChanger script of the Button object to the Button object.
Run the game, click the Button object, and the color will change randomly.

Note:

A Graphics Raycaster component needs to be added to the Canvas object in order for PhysicsRaycaster to work.

Example 2: Dragging Objects

using UnityEngine;
using UnityEngine.EventSystems;

public class ObjectDragger : MonoBehaviour, IPointerDownHandler, IDragHandler
{
    private RectTransform rectTransform;

    private void Start()
    {
        rectTransform = GetComponent<RectTransform>();
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        rectTransform.SetAsLastSibling();
    }

    public void OnDrag(PointerEventData eventData)
    {
        rectTransform.anchoredPosition + = eventData.delta;
    }
}

Steps:

Create a Canvas object and create an Image object under the Canvas.
Set the Event Mask property of the Image object’s PhysicsRaycaster component to its default value.
Mount the ObjectDragger script of the Image object to the Image object.
Run the game, click on the Image object and drag it. The Image object will follow the mouse or touch movement.

Note:

A Graphics Raycaster component needs to be added to the Canvas object in order for PhysicsRaycaster to work.

Example 3: Click the button to play the sound effect

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class ButtonSoundPlayer : MonoBehaviour, IPointerClickHandler
{
    public AudioClip soundClip;

    private Button button;
    private AudioSource audioSource;

    private void Start()
    {
        button = GetComponent<Button>();
        audioSource = GetComponent<AudioSource>();
        audioSource.clip = soundClip;
    }

    public void OnPointerClick(PointerEventData eventData)
    {
        audioSource.Play();
    }
}

Steps:

Create a Canvas object and create a Button object under the Canvas.
Set the Event Mask property of the Button object’s PhysicsRaycaster component to its default value.
Add an AudioSource object to the scene and drag the sound effect file to the soundClip property of the ButtonSoundPlayer script.
Attach the ButtonSoundPlayer script of the Button object to the Button object.
Run the game, click the Button object, and the sound effects will play.

Note:

A Graphics Raycaster component needs to be added to the Canvas object in order for PhysicsRaycaster to work.

Example 4: Click the button to display/hide objects

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class ButtonObjectToggler : MonoBehaviour, IPointerClickHandler
{
    public GameObject targetObject;

    private Button button;

    private void Start()
    {
        button = GetComponent<Button>();
    }

    public void OnPointerClick(PointerEventData eventData)
    {
        targetObject.SetActive(!targetObject.activeSelf);
    }
}

Steps:

Create a Canvas object and create a Button object under the Canvas.
Set the Event Mask property of the Button object’s PhysicsRaycaster component to its default value.
Create an object that needs to be shown/hidden in the scene, and drag the object to the targetObject property of the ButtonObjectToggler script.
Attach the ButtonObjectToggler script of the Button object to the Button object.
Run the game, click the Button object, and the object will be displayed or hidden.

Note:

A Graphics Raycaster component needs to be added to the Canvas object in order for PhysicsRaycaster to work.

Example 5: Click the button to switch scenes

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class ButtonSceneSwitcher : MonoBehaviour, IPointerClickHandler
{
    public string targetSceneName;

    private Button button;

    private void Start()
    {
        button = GetComponent<Button>();
    }

    public void OnPointerClick(PointerEventData eventData)
    {
        SceneManager.LoadScene(targetSceneName);
    }
}

Steps:

Create a Canvas object and create a Button object under the Canvas.
Set the Event Mask property of the Button object’s PhysicsRaycaster component to its default value.
Create a target scene that needs to be switched to in the scene, and drag the name of the target scene to the targetSceneName property of the ButtonSceneSwitcher script.
Attach the ButtonSceneSwitcher script of the Button object to the Button object.
Run the game, click the Button object, and the scene will switch to the target scene.

Note:

A Graphics Raycaster component needs to be added to the Canvas object in order for PhysicsRaycaster to work.