Unity Platform 10 Enermy Basic
===
2020.08.16

###### tags: `platform`

## List
1. [Structure of Enermy](#SE)
2. [Enermy State](#ES)
3. [State : Moving](#SM)
4. [State : Knockback](#SK)
5. [State : Dead](#SD)
6. [Dash FIX](#DF)

## Content
### Structure of Enermy<a id="SE"/>
Enemry state are dead or alive.<br>Alive also devides walking, knockback, chase, etc...<br>We consider this state, so component like this<br>`RigidBody2D`, `Animator`, `SpriteRenderer`, `BoxCollider2D` and Enemry Obj's child alive obj + dead particle(or alive obj+ dead obj)<br>Animation & animator & particle refer to below.<br><br>&nbsp;&nbsp;&nbsp;&nbsp;[Animation ref](https://www.youtube.com/watch?v=K2SbThbGw6w&list=PLy78FINcVmjA0zDBhLuLNL1Jo6xNMMq-W&index=12) 4:00 ~<br>&nbsp;&nbsp;&nbsp;&nbsp;[Animator ref](https://www.youtube.com/watch?v=K2SbThbGw6w&list=PLy78FINcVmjA0zDBhLuLNL1Jo6xNMMq-W&index=12) 5:00 ~<br><a id="REF"/>&nbsp;&nbsp;&nbsp;&nbsp;[Particle ref](https://www.youtube.com/watch?v=K2SbThbGw6w&list=PLy78FINcVmjA0zDBhLuLNL1Jo6xNMMq-W&index=12) 37:00 ~<br><br>In Script, variable like this.

// GameObj
private GameObject alive;
private Rigidbody2D aliveRb2D;
private Animator aliveAnim;
    
private void Start()
{
    alive = transform.Find("Alive").gameObject;
    aliveRb2D = alive.GetComponent<Rigidbody2D>();
    aliveAnim = alive.GetComponent<Animator>();
}

### Enermy State<a id="ES"/>
Enermy States are various. But this example show 3 State, `Moving` `Knockback`, `Dead`.<br>`enum` makes Macro with sucessvie numbers.

private enum State
{
    Moving,
    Knockback,
    Dead
}

private State currentState;
    

<br>

And every state has 3 function Enter, Update Exit.<br>And Switch function for func from one state to other state.<br>state update functions work in `Update()`

// Update Check EveryState
private void Update()
{
    switch(currentState)
    {
        case State.Moving :
            UpdateMovingState();
            break;
        case State.Knockback :
            UpdateKnockbackState();
            break;            
        case State.Dead :
            UpdateDeadState();
            break;
    }
}

//----Moving State---- and other states also like this
private void EnterMovingState() { }

private void UpdateMovingState() { }

private void ExitMovingState() { }

// Switch function.
private void SwitchState(State state)
{
    switch (currentState)
    {
        case State.Moving :
            ExitMovingState();
            break;
        case State.Knockback :
            ExitKnockbackState();
            break;
        case State.Dead :
            ExitDeadState();
            break;
    }

    switch (state)
    {
        case State.Moving :
            EnterMovingState();
            break;
        case State.Knockback :
            EnterKnockbackState();
            break;
        case State.Dead :
            EnterDeadState();
            break;
    }
    currentState = state;
}

<br>

### State : Moving<a id="SM"/>
For moving, grounding must be set.<br>Their technic is same players. But apply it differently.<br>if not grounded or meet wall, enemry flip, else just walk.

// Object Detection
[SerializeField]
private Transform groundCheck, wallCheck;
[SerializeField]
private LayerMask whatIsGround;
[SerializeField]
private float groundCheckDistance, wallCheckDistance;
private bool groundDetected, wallDetected;

// Movement
[SerializeField]
private int facingDirection;
private float movementSpeed;
private Vector2 movement;

private void UpdateMovingState()
{
    groundDetected = Physics2D.Raycast(groundCheck.position, Vector2.down, groundCheckDistance, whatIsGround);
    wallDetected = Physics2D.Raycast(wallCheck.position, Vector2.right, wallCheckDistance, whatIsGround);

    if (groundDetected || wallDetected)
        Flip();
    else
    {
        movement.Set(movementSpeed * facingDirection, aliveRb2D.velocity.y);
        aliveRb2D.velocity = movement;   
    }
}

private void Flip()
{
    facingDirection *= -1;
    alive.transform.Rotate(0.0f, 180.0f, 0.0f);
}

### State : Knockback<a id="SK"/>
Before knockback, must make damage function.<br>Like dummyEnermy, but little changed about direction.<br>Show below.

/*
*     attackDetails[0] = attack Damage
*     attackDetails[1] = attack Position(Player position)
*/
private void Damage(float[] attackDetails)
{
    
    currentHealth -= attackDetails[0];

    //Make particle
    Instantiate(hitParticle, alive.transform.position, Quaternion.Euler(0.0f, 0.0f, Random.Range(0.0f, 180.0f)));
        
    //Set knockback direction
    if (attackDetails[1] > alive.transform.position.x)
        damageDirection = -1;
    else
        damageDirection = 1;

    if (currentHealth > 0.0f)
        SwitchState(State.Knockback);
    else
        SwitchState(State.Dead);
}

<br>

Knockback technic is same players.<br>Time duration and movespeed, set animation.

private void EnterKnockbackState()
{
    knockbackStartTime = Time.time;
    movement.Set(knockbackSpeed.x * damageDirection, knockbackSpeed.y);
    aliveRb2D.velocity = movement;
    aliveAnim.SetBool("Knockback", true);
}

private void UpdateKnockbackState()
{
    if (Time.time >= knockbackStartTime + knockbackDuration)
        SwitchState(State.Moving);
}

private void ExitKnockbackState()
{
    aliveAnim.SetBool("Knockback", false);
}

### State : Dead<a id="SD"/>
If dead, particles are made, and destroy enermy.<br>Particle ref above [link](#REF)

private void EnterDeadState()
{
    Destroy(gameObject);
    Instantiate(deathChunkParticle, alive.transform.position, deathChunkParticle.transform.rotation);
    Instantiate(deathBloodParticle, alive.transform.position, deathBloodParticle.transform.rotation);
}

### Dash FIX<a id="DF"/>
Dash Image's litte problem with time rate.<br>

// before : alphaMultiplier = 0.05f;
[SerializeField]
private float alphaDecay; //Maybe 10?

private void Update()
{
    // before : alpha *= alphaMutiplier
    alpha -= alphaDecay * Time.deltaTime; //
    
}

[Dash rate fix](https://www.youtube.com/watch?v=K2SbThbGw6w&list=PLy78FINcVmjA0zDBhLuLNL1Jo6xNMMq-W&index=12) 43:00 ~<br>