TRANSFORM.TRANSLATE VS RIGIDBODY MOVEMENT IN UNITY
A side-by-side technical breakdown of kinematic vertex translation versus PhysX force integration, collision tunneling, and performance impacts.
1. High-Level Comparison Summary
Collision Behavior: Passes straight through walls unless manually raycasted. Ignores friction and mass.
Execution: Runs in
Update() with Time.deltaTime.Best For: Moving platforms, floating pickups, UI icons, and cutscene tracks.
Collision Behavior: Automatically pushes against solid colliders, respects gravity, angular torque, and friction.
Execution: Runs in
FixedUpdate() with Time.fixedDeltaTime.Best For: Vehicles, aircraft, ragdolls, and physics puzzle blocks.
2. Why Transform.Translate Passes Through Walls
When you execute transform.Translate(Vector3.forward * speed * Time.deltaTime) on a GameObject with a BoxCollider, Unity is effectively teleporting the mesh to a new point in space without sweeping the volume between the old and new positions.
If the translation distance exceeds the thickness of a solid wall, the object ends up on the other side without ever firing an OnCollisionEnter event!
If you must move a Rigidbody while maintaining kinematic control, use Rigidbody.MovePosition() instead. This sweeps the collider through 3D space, preventing tunneling:
using UnityEngine;
[RequireComponent(typeof(Rigidbody))]
public class KinematicPlatform : MonoBehaviour
{
[SerializeField] private Vector3 movementDirection = Vector3.up;
[SerializeField] private float speed = 2f;
private Rigidbody rb;
private void Awake()
{
rb = GetComponent<Rigidbody>();
rb.isKinematic = true; // Kinematic allows script-driven physical sweeping!
}
private void FixedUpdate()
{
// ✅ Sweeps the physical platform and carries any player standing on top
Vector3 newPos = rb.position + movementDirection * speed * Time.fixedDeltaTime;
rb.MovePosition(newPos);
}
}3. Quick Decision Tree
- Is it a player character that needs snappy, arcade platformer jumping? → CharacterController.Move()
- Is it an aircraft, car, missile, or rolling boulder with mass? → Rigidbody.AddForce() / velocity
- Is it an elevator or moving hazard that must push other objects? → Rigidbody.MovePosition() (isKinematic = true)
- Is it a purely visual coin spinning in place or an off-screen UI element? → Transform.Rotate() / Transform.Translate()
Related Topics & Error Troubleshooting
Frequently Asked Questions
transform.position while PhysX is simulating forces creates violent physics desynchronizations, causing the object to violently bounce, glitch through colliders, or trigger severe CPU spikes.