How do I delete everything in the level on level change

Unity Engine
1

I’m making a bullet hell game and for some reason, the projectiles on screen still appear when I change the level. How can I fix this?

2

Hello,
Are you changing the scene?

3

There’s too little info to assume much at this point. Can you provide some info such as, how you load a new level? If a completely new scne was loaded, barring some persisten objects. or another additive scene, this shouldnt be the case. I suspect something is afoul in your loading, but without all the info, its just assumptions.

4

Some ideas:

  • something is marking those projectiles DontDestroyOnLoad()

  • you’re not actually changing the scene

You must find a way to get the information you need in order to reason about what the problem is.

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer or iOS: How To - Capturing Device Logs on iOS or this answer for Android: How To - Capturing Device Logs on Android

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

1 Like
5

OK
the code I use is this:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class ToLevel : MonoBehaviour
{
    public string levelToLoad;
    public string levelToUnload;

    public void ChangeLevel()
    {

        SceneManager.LoadScene(levelToLoad);
        SceneManager.UnloadSceneAsync(levelToLoad);
    }
}
6

That’s nice.

Everything I said in this line still holds potentially true:

Either Destroy them yourself when you change levels, or else don’t mark them as DontDestroyOnLoad()

1 Like
7

That cannot be correct either BTW. Read your variable names closer.

ALSO: you do not need to unload the previous scene when loading a new scene.

Are you using additive scene loading? If so then 100% of your scene loader is not useful, and 100% of your lifecycle of objects will need to be directly managed, either by parenting or by Destroy().

BEFORE doing anything with additive scene loading, I HIGHLY recommend you get it working without.

If not, I highly recommend you create a small simple testbed set of scenes to get your mind around additive scene loading. It has its various pitfalls and requires great care and attention to lifecycles and timing, especially timing related to when the assets actually arrive in scene and can be utilized. Hint: it isn’t instantaneously, it’s at the end of the current frame.

Here’s more reading in case you are interested in additive scene loading.

https://discussions.unity.com/t/820920/2
https://discussions.unity.com/t/820920/4

https://discussions.unity.com/t/824447/2

A multi-scene loader thingy:

https://pastebin.com/Vecczt5Q

My typical Scene Loader:

https://gist.github.com/kurtdekker/862da3bc22ee13aff61a7606ece6fdd3

Other notes on additive scene loading:

https://discussions.unity.com/t/805654/2

Timing of scene loading:

https://discussions.unity.com/t/813922/2

Also, if something exists only in one scene, DO NOT MAKE A PREFAB out of it. It’s a waste of time and needlessly splits your work between two files, the prefab and the scene, leading to many possible errors and edge cases.

Two similar examples of checking if everything is ready to go:

https://discussions.unity.com/t/840487/10

https://discussions.unity.com/t/851480/4

8

thanks for the help!