Unity Foundations·From empty scene to playable build

C# components and the update loop

A MonoBehaviour is a component; its lifecycle methods are your timing contract.

Beginner 15 min read Lesson 7 of 300 Challenge included

What you will be able to do

Cache GetComponent results in Awake.
Use Time.deltaTime for frame-rate-independent movement.
Do not do physics in Update; use FixedUpdate for Rigidbody forces.

In plain English

Awake runs before Start; Update runs every frame; FixedUpdate is for physics. Keep Update small, cache component references and avoid allocating every frame. Separate input, movement and presentation into components.

PlayerController.csC#

using UnityEngine;

public class PlayerController : MonoBehaviour
{
    [SerializeField] private float speed = 6f;
    private Rigidbody body;
    private Vector3 input;

    private void Awake()
    {
        body = GetComponent<Rigidbody>();
    }

    private void Update()
    {
        input = new Vector3(
            Input.GetAxisRaw("Horizontal"),
            0f,
            Input.GetAxisRaw("Vertical"));
    }

    private void FixedUpdate()
    {
        body.MovePosition(body.position + input.normalized * speed * Time.fixedDeltaTime);
    }
}

Your turn

Move a player

Medium

Cache a Rigidbody and move it with normalized input in FixedUpdate.

CSHARP · starter

void FixedUpdate() {}

Check your understanding before moving on.

Knowledge checkQuestion 1

Which loop is appropriate for Rigidbody physics?

Select an answer to continue

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Next: Physics, colliders and triggers

Lesson 7 of 300 · 0% of course