I’m encountering an issue with AI character instantiation in Unity. When I drag my AI prefab directly into the scene through the editor, everything works perfectly. However, when I instantiate the identical prefab during runtime using code, the AI behaves incorrectly.
The main problem occurs with the ThirdPersonCharacter component on my AI agent. Instead of playing the proper walking animation, the character stays in idle animation and slides across the ground to reach its destination.
I’ve traced the issue to the ground detection system. The CheckGroundStatus method seems to fail, and this line of code doesn’t execute properly:
characterAnimator.applyRootMotion = false;
This makes the character slide instead of transitioning to the walk animation state. The ground detection appears to be the root cause, but I can’t figure out why the same prefab behaves differently when spawned via script versus placed in the editor. What could cause this difference in behavior between editor placement and runtime instantiation?
Had this exact problem on a project last year. The issue is usually that runtime instantiated objects don’t go through the same initialization sequence as scene objects.
What’s happening is your prefab’s components aren’t fully awake and started when you spawn it. The ground detection fails because the colliders or rigidbody aren’t properly initialized yet.
Here’s what worked for me - after instantiating, disable the AI movement temporarily and re-enable it after a frame or two:
Alternatively, check if your prefab has any Start() or Awake() methods that set up the ground detection. Runtime spawned objects might not have these fully executed before your movement code kicks in.
I also found that sometimes the NavMeshAgent component needs a frame to properly register with the navigation system. You might want to verify the agent is on the NavMesh before starting movement.
This video explains component initialization timing really well:
The key is making sure all your dependencies are ready before the AI starts trying to move around.
This sounds like a timing issue with component initialization during runtime instantiation. I’ve run into similar problems before and it usually comes down to the order in which components get initialized when spawned via code versus being present in the scene from start. The ground detection system likely relies on physics queries or collider checks that aren’t ready immediately after instantiation. When you place the prefab in the editor, Unity has time to properly initialize all physics components during scene loading. With runtime spawning, your CheckGroundStatus method might be executing before the colliders are fully registered with the physics system. Try adding a small delay after instantiation before your AI starts moving, or implement a coroutine that waits for the physics system to be ready. You could also check if the collider bounds are properly set before running ground detection. Another approach is to ensure your AI doesn’t start pathfinding until all required components report they’re initialized properly.
