I’m running into a weird issue with my AI character setup. When I drag my AI prefab directly into the scene through the Unity editor, everything works perfectly. But when I instantiate the exact same prefab during gameplay using code, the AI starts acting strange.
The main problem is with the ThirdPersonCharacter component on my AI. Instead of playing the walking animation when moving to a target, it just slides around while stuck in the idle animation. I traced the issue to the “CheckGroundStatus()” method where this line seems to be causing trouble:
characterAnimator.applyRootMotion = false;
It looks like the ground detection isn’t working properly for the runtime-spawned version, but I can’t figure out why the same prefab would behave differently depending on how it gets into the scene. Has anyone encountered this before? What could be different between editor placement and runtime instantiation that would affect ground detection?
Physics initialization order is your problem. When you spawn at runtime, the CharacterController and Rigidbody haven’t settled into the physics world yet, so your ground detection raycast gets messed up. I hit this exact issue with my AI system last year. CheckGroundStatus() was running before the character controller actually made contact with ground colliders. In the editor, everything has time to initialize before play starts. Add a short wait after spawning before your AI moves. Something like yield return new WaitForFixedUpdate() twice usually works. This lets the physics system establish proper ground contact. Also double-check your spawn position. I found that spawning characters even 0.1 units too high breaks the initial ground check, leaving the animator stuck until the next successful ground detection.
Had this exact headache 6 months ago with a similar setup. It’s usually timing related.
When you place a prefab in the editor, everything initializes in order. But runtime instantiation messes with that order, especially if your ground detection needs other components ready first.
Check if your AI prefab depends on terrain layers or ground detection that aren’t fully loaded when you instantiate it. I fixed mine by adding a small delay or using a coroutine to wait a frame before enabling the AI behavior.
Try this: after instantiating, disable the ThirdPersonCharacter component, wait one frame, then re-enable it. Gives Unity time to properly initialize all the physics and collider relationships.
Also check if you’re instantiating at the exact same Y position as your editor version. Being slightly off the ground on spawn can break initial ground detection.
Sounds like a layer mask or physics setup issue. I had the same problem where runtime spawned characters behaved differently with collision detection. Check if your instantiation code is accidentally putting the prefab on the wrong layer. Your ground detection raycast might be hitting different colliders or missing them completely if the layer relationships don’t match up. Also found that the Animator component sometimes needs a frame or two to sync properly with the character controller when spawned at runtime. Root motion calculations can get wonky during initialization. Try logging the actual ground detection raycast results for both versions - I bet the runtime version is hitting different objects or getting different distance values. Make sure your ground layer mask is set right in the prefab and the spawn position has enough clearance above ground.