I’m building a 2D Unity game and using the A* pathfinding library for navigation. The pathfinding works great overall - my AI characters find routes correctly and dodge obstacles as they should.
But there’s this weird issue with the Z axis position. My bot spawns at Z=0 and needs to reach a destination that’s also at Z=0. However, while moving along the calculated route, the AI character’s Z coordinate keeps changing randomly between -9 and -1.
I checked the waypoints on the path and they all show Z=0 like they should. The spawning prefab also has its transform set to (0,0,0) initially. I followed all the 2D setup instructions from the documentation and didn’t change any of the package code.
What might be causing this Z position drift in a 2D setup?
Had this exact bug last year on a mobile game. It’s your movement interpolation code.
When lerping between waypoints, only interpolate X and Y values. If you’re doing Vector3.Lerp(currentPos, targetPos, t) and your current position has a slightly off Z value, it’ll keep spreading that error.
Check for animation components on your AI agent too. Unity’s animation system adds tiny Z offsets even in 2D mode, especially if the animator was originally set up in 3D.
Quick debug: add a constraint in your movement update loop that forces Z to always be 0. Try transform.position = new Vector3(transform.position.x, transform.position.y, 0) at the end of your movement function. If that fixes it, something in your movement chain is messing with the Z value.
This Z coordinate drift is probably floating point errors building up during movement calculations. With A* and continuous waypoint movement, tiny calculation errors stack up and cause Z drift even when your waypoints are fine. I had the same issue in a tower defense game - units kept sinking into negative Z values. Turned out deltaTime multiplications in my movement code were the problem, and I wasn’t clamping the Z axis. Physics can mess with this too - 2D colliders sometimes create small Z forces during collisions. Freeze Z position in your Rigidbody2D constraints if you haven’t already. Check any tweening libraries you’re using - they might affect all three axes instead of just X and Y. Sometimes you just need to reset Z position in your movement coroutine or update method.
This sounds like a camera or rendering issue, not pathfinding. Check if your AI agent has physics components - a Rigidbody2D with gravity can cause weird Z movement even in 2D games. Also make sure your camera’s set to orthographic for 2D. Another common problem is multiple scripts modifying the transform position at the same time. If you’re using transform.position instead of transform.Translate(), you need to preserve the Z coordinate by setting it to 0 each frame or using Vector3 with z=0 when updating position. I had the same issue when my movement script kept overwriting coordinates from other components.
i had a similar issue! your A* script might be directly setting transform.position = waypoint, which messes with the z value. use transform.position = new Vector3(waypoint.x, waypoint.y, 0f) to fix it. also, check if colliders are messing with z pos!