Author: digm520admin

August 26, 2019

Tower Defense Tutorial Project

Fixing Scene Transition Between Levels When Continuing

I was able to clean up the scene management enough last time that going through the basic starting game scenes all worked well as far as I could tell. I could get from the main intro scene, to the level select screen, to level 1 without any issues. Progressing to level 2 was not working because of some reference with the enemy spawner object, so I will be looking into that.

PROBLEMS

PROBLEM #1

Level 2 does not load after playing Level 1 because of some reference issue for setting the spawn object.

The error was actually that spawnPoint in WaveInformation was not assigned, so I looked into that and saw that there was a public field for drag/dropping the spawn point object into that I just hadn’t done in Level 2.

SOLUTION: Just setting this public field with the spawn point allowed the level to work properly.

General Testing

I edited Level 2 a bit more just to make sure the data was all being passed over to the WaveSpawner. I made sure to move the starting spawn point just in case that wasn’t being updated and it just worked out visually since they were spawning from the same place as before. I also changed up the map layout and moved the waypoints around to fit this new layout. Running this updated level layout worked as expected, everything was properly updated when opening Level 2.

I had not tested using the Continue button from Level 1 since Level 2 was not working in any capacity until now, so I tried that now. This seemed to open Level 2 fine and ran the level, but it did not end when the last enemies were destroyed. I then tried using the pause menu to retry the level and this gave an error saying the SceneManager tried to SetActive an invalid scene.

Going to Level 2 from the level select menu seems to give no errors. The game ends with the player winning as expected, and the Retry and Menu options from the pause menu both work as intended. Something is being messed up when transferring directly from Level 1 to Level 2 with the Continue button function.

PROBLEM #2

Using the Next level option on the level complete screen is giving some errors. Most notably, the level complete screen does not come up on the next level when the player completes it, and using Retry on the level returns a scene error.

The Retry level error makes sense. The SceneManagerLite holds a reference to an int called currentLevelBuildIndex that is supposed to represent the scene index of the currently loaded level scene. This however is not being properly set when using the NextLevel method, so the RetryLevel method in SceneManagerLite refernces the currentLevelBuildIndex to determine which scene to load, and is actually seing the last level’s index here. So what is happening is that it is loading the last level scene, then unloading it, and then trying to set it active. Since it is now unloaded, there is nothing to set active resulting in the error.

I believe the game not ending is as simple as the GameIsOver bool in the LevelManager not being reset. This is initialized on false, and set to true when the level does end. However, going straight from one level to the next never unloads the Base scene which contains the object holding the LevelManager, so that is never reset to false.

Test #1:

Two fold test: Properly set the currentLevelBuildIndex within the NextLevel method (in a way similar to the SelectLevel method); also reset the GameIsOver bool in LevelManager when using the NextLevel method.

Editing the NextLevel method in the SceneManagerLite was simple enough to just add setting the currentLevelBuildIndex to the proper value, but figuring out exactly where to reset the GameIsOver bool was a bit tricky. I wanted to place it somewhere where the reference to the LevelManager fit in cleanly, but it also needed to be somewhere that could set the value after calling a method like RetryLevel or NextLevel from the SceneManagerLite. (RetryLevel may be important for when the game ends from the player losing the level, or if we want to add a retry option even on completeing the current level). Setting it too early might cause issues where the game tried to end again while loading/unloading scenes.

SOLUTION 1: Setting the currentLevelBuildIndex in the NextLevel method of SceneManagerLite fixed problems loading the scene using NextLevel, as well as fixing the menu errors in game. Now using Retry and Menu after loading into a level with NextLevel work properly.

On the other end, I tried to fix the GameIsOver bool by creating a new script called LevelInitializer and placing it on to the LevelInformation object found in level scenes. This script simply attempts to get a reference to the LevelManager (which now has a static method and reference to be gotten) and ensure the LevelManager is properly reset when a level starts. This is done in the new LevelInitializer script’s Start method, the thought here being that this should be called anytime a level scene is loaded, which is exactly when we want to ensure the LevelManager is reset. However, the game still was not ending after continuing from level 1 to 2.

Test #2:

I only needed to fix the second part of the problem now, and it seemed to be a rather easy fix. It turns out, since the LevelInformation object I added the LevelInitializer script to wasn’t a prefab (it is now thanks to this issue), I only added LevelInitializer to Level 1. So Level 2 did not have this script at all, so it had no way to run the new reset method I created.

SOLUTION 2: I just needed to actually add the LevelInitializer script onto the LevelInformation object in every level scene. Doing this reset the LevelManager as intended so the player can now win when they use the Continue menu option on the level complete screen.

NEXT STEP

The scene management is almost completely finished and looking to work pretty well. The main process to test next will be losing conditions, since I have not checked that in a while. This may have a few kinks that I need to fix out since it has not been through the same testing as winning and progressins, but it should hopefully be some quick easy fixes if any.

August 24, 2019

Tower Defense Tutorial Project

Fixing Problems with the Scene Manager

A major issue I may have to deal with is updating the version of this Unity project. To clean out space on my computer, I wanted to condense the versions of Unity I was using on several projects so I removed one of the older 2018 versions I was using originally for this tutorial. I wanted to upgrade it to a 2019 version, so I just used the most recent one I had. I don’t believe this should have very major impacts on this project, but it is worth noting for any extra strange behavior or errors.

First things first, I need to do a bit of play testing to get a feel for the current errors and go over the main scripts (mostly those dealing with scene management) to see where to start. The opening scenes seem to work well (the initial main scene into the level select menu). Selecting level one works ok. Any other level leads to weird errors (not properly closing other scenes so lights add up and UI elements stack on top of each other), which is expected since my work focused on getting level 1 to work first. Retrying while a wave is spawning leads to some interesting behavior (it spawns the second wave instead of the first when the level restarts).

To make it easier to keep track of all the different scripts, I started organizing the scripts folder hierarchy. This began with simply creating any hierarchy at all, as initially I just had all of the scripts in the scripts base folder. While it may be a bit risky since I do move things around from time to time at this stage, I decided it would make sense to make a folder for each scene and organize the scripts by scene basically at the first level. This would help me see which scripts are running in which scenes simply by checking the folders. And when I am in a certain scene, I can just open its corresponding scripts folder to see what all is available.

This was actually a very straight forward way of placing a lot of the scripts. Many of them pretty directly only exist in one scene that makes sense. Some of the more instantiated object related scripts (like for the turrets and the enemies) pretty clearly made sense to just put in the Level scene folder since that’s where they should be instantiated so they were easy to place as well.

PROBLEMS

PROBLEM #1

Restarting a level while the first wave is still spawning will have the second wave spawn first on restart.

This is most likely an error that happens because restarting while the coroutine is running for spawning a wave has the value reset that happens when restarting overridden by the coroutine then ending. Checking the WaveSpawner script affirms my assumption since it has a method called ResetWaveSpawner, which sets the waveIndex to 0 (the first wave) but the coroutine spawning the wave, called SpawnWave, increases the waveIndex by 1 once it is finished running. The coroutine is most likely “finishing” after the reset is happening, so the index gets pushed to 1 immediately (insted of being at 0 as it should).

Test #1:

Add a check to ResetWaveSpawner to see if the SpawnWave coroutine is running and stop it before resetting.

This is a perfect opportunity to try the new way I learned to control the flow of coroutines. Instead of using an outside bool variable that is set to true when the coroutine starts, false when it ends, and checking later if that bool is true/false to stop the coroutine, you can control an IEnumerator reference. You first create an IEnumerator reference variable. You then set this equal to the coroutine you want to start right before starting it, then Start this reference variable as your coroutine. When you want to check if it’s running or not later to determine if it needs stopped, you can just do a check to see if this reference variable is not null and then stop the coroutine.

SOLUTION: This worked perfectly. Restarting at anytime (even immediately when the wave starts) has the proper wave spawn. This also stopped the case of enemies continuing to spawn (which was the same issue of the coroutine running into the next scene start, it was just a longer coroutine in that error).

PROBLEM #2

The level does not end when the player defeats the final wave.

The LevelManager script that ultimately starts the “winning process” has a lot of conditions to start this process. The if statement checking in Update to see if the player has won has 4 separate conditions, so there is a high chance one of these is not acting as it should. This is a good place to start looking for why this error occurs. The conditions are as follows:
if (waveSpawnerReference.isActiveAndEnabled && waveSpawnerReference.WavesFinished() && waveSpawnerReference.enemiesAlive == 0 && GameIsOver == false)
{
WinLevel();
}

waveSpawnerReference.WavesFinished() is a method that does a bool check in the WaveSpawner script, so my first thought was to check there and make sure it was being set properly. I simply tested this condition with GameIsOver == false to prompt winning to see what this did. This resulted in the player winning immediately on the level starting. I then remembered, this is a scene loading timing issue reflected in the WavesFinished method check. This method is:
public bool WavesFinished()
{
if(waveIndex == waves.Length)
{
wavesFinished = true;
}
return wavesFinished;
}
The reason this checks as true immediately is because the method gets called before any of the values are set, so the waveIndex is 0 by default (which is accurate) but the waves.Length, which should be the count of how many waves are in the level, is also defaulted to 0 before being set. This results in this being true at frame one.

Looking at the WaveSpawner, I see why these conditions are not being met simultaneously. The WaveSpawner has an Update check to see if the waveIndex == waves.Length to indicate that the last wave has been spawned, and if this check is true, if disables itself. So the condition including a check for hitting the end of the waves AND seeing if the WaveSpawner is enabled will never be true simultaneously.

Test #1:

Create a DeactivateWaveSpawner method which will allow me to deactivate the spawner with the LevelManager AFTER performing the check to see if it’s active for winning (and just after calling the losing method for continuity).

I also had to tweak the WaveSpawner script a bit since it was in charge of deactivating itself as soon as it spawned the final wave. I wanted it to stay active until the player won or lost, and then have those methods deactivate it. This method however gave me very interesting errors. It still was having the player win immediately the first time I selected level 1, but every subsequent time I selected level 1 from the level select menu, it worked perfectly fine. It started properly and allowed the player to win correctly.

Once again, this is an annoying timing issue. The WaveSpawner actually starts enabled in when starting the game from scratch in the Logic scene. The WaveInformation script in the tested Level scene contains the following:
private void Start()
{
waveSpawnerReference = WaveSpawner.GetInstance();

// Reset the wave spawner each time a level loads
waveSpawnerReference.resetWaveSpawner();

PassWaveInformation();
waveSpawnerReference.enabled = true;
}
What’s happening is that the necessary values are being passed to the WaveSpawner through the PassWaveInformation method and the game is immediately ending with a win and then deactivating the WaveSpawner. Now on returing to level 1, the values needed are already set, and these statements before the final statement which enables the WaveSpawner are fed into nothing (since the WaveSpawner is disabled at that time). Now however, anything that checks the values of WaveSpawner will be checking the correct values as intended since they were set way back when the level was previously started. This is removing any frame perfect timing check errors since everything is set before the WaveSpawner is even turned on, but only when starting the level after the first run.

Test #2:

Edit the conditions in the WavesFinished method in the WaveSpawner to be more accurate.

SOLUTION: The general idea is that this is basically returning a false positive check by immediately checking the default value to meet its only condition, so I am just going to add another check to make sure a default case that doesn’t make sense to ever happen anyway isn’t what one of the current values is set to. So basically I changed the condition from:
if(waveIndex == waves.Length)
to
if(waves.Length != 0 && waves.Length)
No level should ever have 0 waves in it anyway, so this check is safe for my game environment and removes the false positive check with the default values where everything is initially at 0.

Using this method worked perfectly, and may also serve as a useful secondary check regardless to reduce the chances of future wave spawning bugs.

PROBLEM #3

The spawn coroutine is still giving some errors in some scene change circumstances.

The main issue with the spawn coroutine was happening when retrying a level, so I specifically fixed a method which was called at the start of loading a level scene so that it would stop the spawn coroutine. However, Unity still doesn’t like that this coroutine continues in other scene swap scenarios (like going back to the menu). It isn’t a game breaking error, but it still shows up as an error in the logs as the game wants to complete the coroutine but cannot because certain objects are not gone (or destroyed according to Unity). This is not a big issue, but I thought it was an interesting enough problem to record as I basically want a consistent way to stop this coroutine when the scenes change.

My first thought was to have a StopCoroutine call in an OnDisable method since that’s a pretty general practice, but unfortunately that does not work here. It would be in the WaveSpawner script which always exists since it’s part of the logic scene. On second thought, this should work because the WaveSpawner should be disabled anytime we leave the Level and Base scene anyway. Fixing that may lead to a nice solution for fixing this error.

Test #1:

Use an OnDisable method in WaveSpawner to stop the SpawnWave coroutine, and follow this by making sure anytime we leave the Level/Base scene we disable the WaveSpawner.

SOLUTION: I looked to the LevelManager and OverlayCanvasManager in the Base scene as these together deal with all of the UI interactions that lead to leaving the current Level and Base scene combination. The main issue was that using Retry and Menu were not deactivating the WaveSpawner, so I looked to add this deactivation into the OverlayCanvasManager where these button functionalities reside.

Since LevelManager already has a reference to WaveSpawner and was deactivating it, I actually just made the WaveSpawner deactivation into a public method, DeactivateWaveSpawner, which called the WaveSpawner’s DeactivateWaveSpawner method, and gave the OverlayCanvasManager a reference to the LevelManager so it could just use this method. I’m not sure if this is better, but it seemed silly to have two seperate references to the same object for the same reason when these two scripts would always be on the same core object anyway.

I then noticed that all my small methods for switching scenes (Retry, Menu, NextLevel) all called the ResetOverlayUI method, which just sets all the UI elements in the level to inactive before switching scenes just in case they would stick around for any reason. Since they all called this method, I just added the DeactivateWaveSpawner reference here, to the ResetOverlayUI method. Now they all deactivate the WaveSpawner before shifting scenes.

This appeared to work, as the error stopped coming up. I even tested with a very large amount of enemies in one wave just to ensure it should still be running after switching scenes had it not been actively stopped. This also meant I could remove stopping the coroutine from the waveSpawnReset method in WaveSpawner without any issue. This was the method referenced by WaveInformation I initially used to solve the weird double spawning issue when restarting a level. This problem is now more cleanly solved as well.

NEXT STEP

Everything seems to work cleanly with Level 1, so the next step is just making sure any level works.