Troubleshooting issues with Unity Behavior

Solve common problems that might arise while working with Unity Behavior.

Default values in RunSubgraph node not updating

When you change a subgraph's Blackboard Variable (BBV) default value, the RunSubgraph field retains its current value as an override instead of updating to the new default.

Resolution:

Revert the RunSubgraph field to its default value.

Stack-overflow issue with SharedBlackboardVariable

A stack overflow occurs at runtime (or playmode) when the graph of a BehaviorGraphAgent attempts to access or set SharedBlackboardVariable.

Causes

A Behavior editor crash might cause incorrect serialization of the SharedBlackboardVariable in RuntimeBlackboardAsset.

Resolution:

Upgrade to Unity Behavior version 1.0.3 or later.

Additionally, check your original Blackboards to ensure no SharedBlackboardVariable is serialized in the RuntimeBlackboardAsset, as this can lead to issues later.

Default value for SharedBlackboardVariable variable is null

A SharedBlackboardVariable on Behavior(Graph)Agent can sometimes have an invalid default value, resulting from the previous stack overflow issue.

Causes

This problem is most likely caused by a SharedBlackboardVariable that's serialized on the RuntimeBlackboardAsset with an invalid value.

Resolution

Perform the following checks to resolve this issue:

  • Use Unity Behavior version 1.0.3 or later, because the SharedBlackboardVariable generation at authoring time is fixed in this version.

  • Check the existing RuntimeBlackboardAsset to ensure it doesn't have any SharedBlackboardVariable serialized in their Blackboard > Variables field. If any is present, follow these steps to regenerate the Variables:

    1. Open the faulty behavior graph.

    2. Add a new Blackboard variable.

    3. Save the graph to refresh the asset.

    4. Delete the new variable.

    5. Save the graph again.

Additional resources