Why does my AI agent behave differently when spawned at runtime versus placed in the editor?

Other Questions AI Agent
1

I’m scratching my head over this weird AI behavior in my game. So, I made this cool AI prefab that works like a charm when I drop it into the scene editor. But here’s the kicker when I try to spawn the same prefab during gameplay, it goes bonkers!

The AI just stands there doing its idle dance, and the CheckGroundStatus() function in the ThirdPersonCharacter script throws a fit. It’s like the AI forgot how to walk! Instead of moving normally, it just slides around like it’s on ice.

void Update()
{
    if (!m_AIController.isGrounded)
    {
        m_Animator.SetBool("IsWalking", false);
        m_AIBody.velocity = Vector3.zero;
    }
    else
    {
        m_Animator.SetBool("IsWalking", true);
        m_AIBody.velocity = m_AIController.desiredVelocity;
    }
}

I’m betting it’s something super simple I’m overlooking, but for the life of me, I can’t figure out why the same prefab acts so differently when spawned. Any ideas what could be causing this Jekyll and Hyde behavior in my AI?

2

hey lucasg, sounds like a pain! have u checked if all the components r properly attached when spawning? sometimes unity can be finicky with that. also, maybe try debuging the ground check - could be the collider or layers actin up. good luck man, let us know if u figure it out!

3

This is a classic case of component initialization issues during runtime spawning. When you place the AI in the editor, all components have time to properly initialize. However, when spawning at runtime, some components might not be fully set up before the Update() method kicks in.

Try moving your AI logic to a coroutine that starts after a short delay, giving all components time to initialize:

void Start()
{
    StartCoroutine(InitializeAI());
}

IEnumerator InitializeAI()
{
    yield return new WaitForSeconds(0.1f);
    // Initialize your AI components here
    // Then enable your Update() logic
}

This should give your AI agent time to properly set up all necessary components before attempting to move or check ground status. Also, double-check that all references (like m_AIController and m_AIBody) are properly assigned when spawning the prefab at runtime.

4

I’ve encountered a similar issue before, and it turned out to be related to the physics simulation. When you spawn the AI at runtime, it might not have enough time to settle properly with the physics system before your scripts start running.

One thing you could try is to disable the AI’s rigidbody for a brief moment after spawning, then re-enable it. This gives the physics engine a chance to properly place the AI on the ground. Here’s a snippet that might help:

IEnumerator EnableAIAfterSpawn(GameObject spawnedAI)
{
    Rigidbody rb = spawnedAI.GetComponent<Rigidbody>();
    rb.isKinematic = true;
    yield return new WaitForFixedUpdate();
    rb.isKinematic = false;
}

Call this coroutine right after spawning your AI. It temporarily makes the rigidbody kinematic, waits for the next physics update, then switches it back. This small delay can sometimes be enough to solve these quirky spawning issues.

Also, double-check your layers and make sure the ground layer is properly set for both editor-placed and runtime-spawned AIs. Sometimes these settings don’t carry over correctly when instantiating prefabs.