4.11 Child blueprint variables resetting to parent defaults

Jules86
Sat, 07 May 2016 19:41:12 +0000
Blueprint

The error:

Child blueprints variables resetting to their parent’s default values upon opening the editor. The type of variables affected include floats, Booleans, vectors and enumerated variables (however the list is not exhaustive as not every variable type is used). Variables which are not inherited from the parent are not affected. It’s worth noting that the parents are custom blueprints and not default classes.
Only blueprints with custom blueprint parents which are placed into the level are affected by this issue, blueprints which are spawned into the level are unaffected.
The variables reset to default upon opening the editor.

It is import to note these variables do not reset to their parent’s defaults whilst the editor is in use, but only after closing and reopening it. Re-opening the level file will not cause it either, only closing and reopening the editor.

For us this is resetting our spawners, we have multiple different types of spawners but they all inherit from a generic spawner class that creates the variables for the maximum number of agents to spawn and the rate at which they are spawned. The generic spawner class also controls the actual spawning functionality, the children override the spawning function and add extra controls and behaviours to it.

The cause:

The cause for us appears to be editing and compiling the player blueprint, which is the pawn for our single player gamemode.

The process for replicating the error is as follows:

1. Edit the Player Blueprint.

2. Compile the Player Blueprint.

3. Save the level.

4. Close the editor.

The values in the variables which get reset can be set before or after the player blueprint is compiled, as long as the level itself is saved after the compile of the player blueprint the error will occur.

Editing the player blueprint, then saving it without a compile, saving the level and then closing and reopening the editor will not result in the error, even though the blueprint is automatically compiled upon reopening the editor.
I want to reiterate that this error only occurs upon reopening the editor and not upon opening the level (to test this I ran through stages 1 to 3 for replicating the error then opened another level and then re-opened the level I had just saved, the values were unchanged; when closing and reopening the editor the values in the level had reset to the parent’s defaults). This also only occurs for levels saved after the player’s blueprint has been compiled and not before, it occurs regardless of whether the level was open at the time of compiling the player blueprint, opening and then saving a level after the compile will result in the error.

Other tests:

Since the player blueprint is the pawn for our single player mode it occurred to me that maybe editing other blueprint that are part of the GameMode classes might also cause the error. I replicated stages 1 to 4 for the custom GameState, the PlayerController and the HUD blueprints, none of which caused the error. I also tested the GameInstance this also did not cause the error.

The game also has a spectator gamemode, so it occurred to me that running through stages 1 to 4 for the spectator pawn might also cause the error, it did not, even when the spectator gamemode was set as the current gamemode.
I also run through stages one to four on the player blueprint whilst the game mode for both the world and the project was set to the default and the error still occurred.

As the player blueprint inherits from the Character class I also ran through stages 1 to 4 on the enemy character (there’s only one in the game so far) as they also inherit from the Character class, this however did not cause the error. The enemy character actually inherits from a generic enemy class that inherits from the Character class, I tried editing both the generic enemy and the child enemy character blueprints, both of which failed to cause the error.

Conclusion:

I’m at a bit of a loss really. Whist I know where the cause is and now how to replicate the error (it has taken two days of solid bug hunting to narrow this down), there doesn’t appear to be a specific link as to why this is the cause. Editing and compiling other blueprints in the game don’t appear to cause the error. At first this appeared to make sense as the player blueprint is the pawn for the gamemode which the level was using, but editing other pawns for other GameModes when they are in use failed to replicate the error.

In short there’s bug which is causing blueprints which have a custom parent blueprint and are placed into a level to reset to their parent’s default values when the player blueprint is edited and compile and then the level is saved, and the editor closed and reopened.

Additional:

The player is spawned into the level by a PlayerStart Actor.

The project started as a UE 4.7 project.

The issue first became present when we updated the project to UE 4.10.0 and still persists in UE 4.11.2.

(Edits for spelling and grammar.)

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