Add a scene

Page update date : Friday, September 29, 2023

Page creation date : Sunday, May 1, 2022

Verification environment

Windows

Windows 11

Unity Editor

2020.3.25f1

Input System Package

1.2.0

Prerequisites for this tip

The following settings have been made in advance as a premise for the description of this tip.

About adding a scene

Unity allows you to display multiple scenes at the same time. Use it when you simply want to overlay scenes or export your drawings to a different texture.

This time, I would like to explain the superimposed display of the scene assuming that the menu screen is displayed in the foreground while the game is running while the game is running.

When displaying multiple scenes, you should be aware of the following:

There must be no more than one EventSystem
There must be no more than one Audio Listener
Be careful when handling multiple cameras

Prepare the scene

This time, we will prepare two scenes. Let be , and SampleSceneParentthe scene SampleSceneChild to be displayed additionally is . The method of preparing two scenes is the same as the previous tips, so please refer to them.

Switch between scenes

This time, we will create the following layout. If you click the button in the parent scene, there is no problem except to add the child scene. and sprites are placed to make it easier to Canvas understand the symptoms that you will see later.

SampleSceneParent

SampleSceneChild

When multiple scenes are displayed, the context of the objects depends on the "layer order" of each object, regardless of the scene unit. Since the initial values are all 0, leave SampleSceneChild Canvas the no and sprites set to "1".

Don't forget to set the two scenes in the build settings.

Processing Scenes

It is processed in code in the same way as switching scenes. This time too, it is processed when the button is clicked, but it is processed as an addition instead of a scene switch.

The name of the script file is arbitrary, but here SceneAdd it is .

The script looks like this:

using UnityEngine;
using UnityEngine.SceneManagement;  // 追加

public class SceneAdd : MonoBehaviour
{
  /// <summary>ボタンをクリックしたときに呼ばれます。</summary>
  public void OnClick()
  {
    // 指定したシーンを追加します
    SceneManager.LoadScene("SampleSceneChild", LoadSceneMode.Additive);
  }
}

When switching scenes, LoadSceneMode I set to , Single but this time Additive it is . That's all there is to the difference.

After SampleSceneParent you save the script, attach it to . EventSystem

Set the method on the OnClick button.

Try running the game to see how it works. If you click the button, you will see the child scene.

Also, if you look at the hierarchy, you can see that there are two scenes.

However, despite the fact that the scene has been added, it seems that the contents of the parent scene's Canvas are not displayed. Conversely, you can see that the sprites in the parent scene are displayed on the back side according to the order of the layers.

Also, if you look at the console, you can see that the logs are constantly output.

The content is the following two points.

There are 2 event systems in the scene. Please ensure there is always exactly one event system in the scene
There are 2 audio listeners in the scene. Please ensure there is always exactly one audio listener in the scene.

When using multiple scenes, it is necessary to correspond to these two points and the camera.

Fix EventSystem errors

The contents of the log are as follows.

There are 2 event systems in the scene. Please ensure there is always exactly one event system in the scene

(There are two event systems in the scene.) Make sure you always have one event system in your scene)

As written, combining the EventSystem into one solution will solve the problem.

SampleSceneParent is assumed to always exist,SampleSceneChild so delete it when EventSystem you open it.

Of course, please note that if you run by itself,SampleSceneChild the UI such as buttons will not work.

You can see that the EventSystem logs have disappeared when you run it.

SampleSceneParent Also, since is EventSystem present, the buttons in the child scene can be activated.

Fix AudioListeners errors

The contents of the log are as follows.

There are 2 audio listeners in the scene. Please ensure there is always exactly one audio listener in the scene.

(There are two audio listeners in the scene.) Make sure there is only one audio listener in the scene at all times. )

Main Camera If you look at the components of , you can certainly see that the Audio Listener exists, so SampleSceneChild you can delete the Audio Listener in . It can be solved by camera control of the next item, so we will deal with it there.

If you want to keep the camera,SampleSceneChild you will delete this Audio Listener.

Change the camera to show two scenes

As for the cause that only the canvas of the child scene is displayed when adding a child scene, This is because there are two cameras, the parent scene and the child scene set on the canvas, and only one camera is displayed.

The solution to this is to display the canvas of both scenes with the camera of the parent scene. The process is to replace the camera on the child scene's canvas with the parent scene's camera after the child scene is added.

Let's create a script. The name is arbitrary, but in this case ChildSceneCamera it is .

The script looks like this: Canvas It is a prerequisite process to attach to .

using System.Linq;
using UnityEngine;
using UnityEngine.SceneManagement;

public class ChildSceneCamera : MonoBehaviour
{
  /// <summary>シーンに追加されたタイミングで処理されます。</summary>
  void Awake()
  {
    // 親のシーンのキャンバスを取得
    var parentScene = SceneManager.GetSceneByName("SampleSceneParent");
    var parentCanvas = parentScene.GetRootGameObjects().First(obj => obj.GetComponent<Canvas>() != null).GetComponent<Canvas>();

    // 子のシーンのキャンバスを取得
    var childCanvas = GetComponent<Canvas>();

    // 子のシーンのカメラを削除
    Object.Destroy(childCanvas.worldCamera.gameObject);

    // 子のシーンのキャンバスのカメラを親のシーンのカメラに置き換えます
    childCanvas.worldCamera = parentCanvas.worldCamera;
  }
}

Awake The method is executed the first time the object exists in the scene. Start Executes before the method. It's good to remember that you often use it often. This time, it is assumed that it will be executed when the child scene is added.

/// <summary>シーンに追加されたタイミングで処理されます。</summary>
void Awake()
{
  // 処理
}

Get the parent scene canvas and the child scene canvas to replace the camera. There are various ways to do it, but it is not the main subject, so you can think that you can get it if you do it this way for the time being.

// 親のシーンのキャンバスを取得
var parentScene = SceneManager.GetSceneByName("SampleSceneParent");
var parentCanvas = parentScene.GetRootGameObjects().First(obj => obj.GetComponent<Canvas>() != null).GetComponent<Canvas>();

// 子のシーンのキャンバスを取得
var childCanvas = GetComponent<Canvas>();

Destroy the child scene's camera Object.Destroy first. Even if it is gone, there is no problem because it can be covered by the camera of the parent's scene. The deletion target Canvas.worldCamera is retrieved from . It's just because the same camera that the scene has at this point is set and can be easily acquired. If you actually want to delete it, you'd better get the camera from the scene.

// 子のシーンのカメラを削除
Object.Destroy(childCanvas.worldCamera.gameObject);

Finally, the child scene Canvas.worldCamera is replaced with the parent's camera.

// 子のシーンのキャンバスのカメラを親のシーンのカメラに置き換えます
childCanvas.worldCamera = parentCanvas.worldCamera;

After SampleSceneChild you save the script, attach it to . Canvas

It is OK if the result of executing and adding a child scene is as shown in the figure below. Make sure there are no logs either.

Switch between scenes

Change the background color of a scene