The central component of any game, from a programming standpoint, is the game loop. It allows the game to run smoothly regardless of a user’s input or lack thereof.
Every game must and should have a game loop because a game must continue regardless of a user's input. In this article, I will be talking about two important event functions in unity3D, i.e.,
Basics of Scripting
Firstly, you need to understand what is unity3D and the importance of scripting (C#/UnityScript) in game development. To do this, you have to visit my technical blog where I blogged the important aspects and concepts of unity2D/3D game development..
Time to Awake() and Start()
By now, you should have understood what the main components and aspects of unity2D/3D game development are. Just to quickly recall, in Unity2D/3D:
- 1 Project = 1 Game
- 1 Level = 1 Scene
Start are two functions that are called automatically when a script is loaded.
When a scene starts,
Awake() is the function which is always called (once for each object in the scene) before any
Start functions. But there are some points to remember:
Awake() is called only after a prefab is instantiated.
- If a
GameObject is in-active during start up,
Awake is not called until it is made active, or a function in any script attached to it is called.
Awake is called first even if the script component is not enabled and is best used for setting up any resources between scripts and initialization.
Start() is called before the first frame update only if the script instance is enabled.
Start is called after
Awake, immediately before the first
Update, but only if the script component is enabled.
- This means that you can use
Start for anything you need to occur when the script component is enabled. This allows you to delay any part of your initialization code until it’s really needed.
Using the Code (C#)
public class AwakeAndStart : MonoBehaviour
void Awake ()
void Start ()
Time for Update() and FixedUpdate()
When you’re keeping track of game logic and interactions, animations, camera positions, etc., there are a few different events you can use. The common pattern is to perform most tasks inside the
Update() function, but there are also other functions you can use.
Update is the most commonly used function in unity. It’s called once per frame on every script that uses it. Almost anything that needs to be changed or adjusted happens here.
- Called Every frame
- Used for regular updates such as:
- Moving Non-Physics objects
- Simple Timers
- Receiving Input
- Update interval times vary
Update is not called on a regular timeline. If one frame takes longer to process, then the time between update calls will be different.
FixedUpdate is a similar function to update but it has a few important differences.
FixedUpdate() is often called more frequently than
Update(). It can be called multiple times per frame, if the frame rate is low and it may not be called between frames at all if the frame rate is high. Fixed Update is called on a regular timeline and will have same time between calls. Immediately after
FixedUpdate is called, any necessary physics calculations are made. As such, anything that effects a rigidbody-meaning a physics object, should be executed in fixed update rather than update.
- Called Every Physics Step
FixedUpdate intervals are consistent
- Used for regular updates such as adjusting physics (Rigibody) objects
If you are planning to change the state of a physics
Using the Code (C#)
public class UpdateAndFixedUpdate : MonoBehaviour
void FixedUpdate ()
Debug.Log("FixedUpdate time :" + Time.deltaTime);
void Update ()
Debug.Log("Update time :" + Time.deltaTime);
- Script Reference: Awake
- Script Reference: Start
Filed under: C#, Gaming, unity
Tagged: C# scripting unity3d, learn unity2d, unity 2d, Unity and C#: Game Loop/ Event Execution Order, Unity engine, unity with C#