Day 3 of Getting Started with Unity: Bullets, Triggers, Tabs, and Invincible Death Animations

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This article describes the firing code of the bullet, the different triggers when the bullet hits different objects, and the animation of the character’s death and invincibility time.

Bullet firing and firing interval

Not much to say, go directly to the code:

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//In the player file:
//Refer to the bullet's model
public GameObject bulletPrefab;
//Setting parameters
// bullet rotation degrees
    private Vector3 bulletEulerAngles;
    // timer
    private float timeVal;

//Add the tank rotation to the previous code that controls the tank's orientation:
//The 2D game is reversed, and it rotates 180 degrees along the x-axis. "The 2D game and UI should be reversed (positive 90 degrees -> negative 90 degrees)"
if (h < 0){
    sr.sprite = tankSprite[3];
    //to the left
    bulletEulerAngles = new Vector3(0,0,90);
}
else if (h > 0){
    sr.sprite = tankSprite[1];
    //rotate right
    bulletEulerAngles = new Vector3(0,0,-90);
        }
if (v < 0){
    sr.sprite = tankSprite[2];
    //under
        bulletEulerAngles = new Vector3(0,0,-180);
}
else if (v > 0){
    sr.sprite = tankSprite[0];
    //Up; the original image is facing up, and it does not need to be set to 180, otherwise it will be the same as the image facing down
        bulletEulerAngles = new Vector3(0,0,0);
}

//The attack method of the tank
    private void Attack(){
        //if the player presses the space bar
        if(Input.GetKeyDown(KeyCode.Space))
        {
            //Instantiate the bullet (game object, tank position, rotation angle)
            //The angle generated by the bullet: the angle of the current tank + the angle the bullet should rotate
            //Rotation in the panel is a quaternion converted to Euler angles, not rotation itself.
            //Use API:Quaternion.Euler to convert quaternion to rotation
            Instantiate(bulletPrefab, transform.position, Quaternion.Euler(transform.eulerAngles + bulletEulerAngles));
            // reset the timeVal timer
            timeVal = 0;
        }
    }

//Bullet shooting interval (attack cd)
void Update(){
        //attack cd
        // Usually timers are placed in Update()
    if(timeVal >= 0.4f){
        Attack();
    }
    //If there is no 0.4f, it will increase with time, so as to achieve the effect of attack interval
    else{
        timeVal += Time.deltaTime;
    }
    }

//Finally, set the rate of fire and movement method in the bullet file:
public float movespeed = 10;
void Update()
    {
        //Not transform.forward, forward is moving along the z axis
        //Should use .up to achieve x-axis movement
        //Translate method with two parameters: the first parameter can be moved along the world coordinate axis,
        //Or move in its own direction,
        //If it is the world, the second parameter does not need to be filled,
        //You can also choose Space.World or Space.Self,
        //Otherwise you must fill in Space.World
        transform.Translate(transform.up * movespeed * Time.deltaTime, Space.World);

Triggers and tags

As we all know, when a bullet hits a wall in a tank battle, it should collide with the wall and disappear. So we set the bullet trigger here: both sides need to have a collider component (Box Collider 2D), one of them must have a trigger (is trigger☑️), and the moving side has a rigid body (Rigidbody 2D ) and set his gravity to 0.

When different objects collide with the bullet, we hope that there will be different results: for example, when the bullet hits the player, it will explode and cause the player to die; when the bullet hits the grass, it will pass through, etc. We can set tags (tag) for convenience:

In the bullet script, we use switch to build the trigger frame:

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//Use the 2D trigger collision->the object hit by the bullet
       public void OnTriggerEnter2D(Collider2D collision){
           switch(collision.tag){
               case "Tank":
               collision.SendMessage("Die");
               break;
               case "Heart":
               break;
               case "Barrier":
               break;
               case "Wall":
               break;
               case "Enemy":
               break;
               default:
               break;
           }

Invincibility and Death

death function

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//Refer to the death animation
public GameObject explosionPrefab;
// Tank's death method
private void Die(){
    //Detect whether the player is in a protected state, if so, return directly without performing the following death effects
    if(isDefended == true){
        return;
    }
    //generate explosion effect
    Instantiate(explosionPrefab, transform.position, transform.rotation);
    //die
    Destroy(gameObject);
}

Invincible time

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//Set the invincibility state
private bool isDefended = true;//The default value of boolean is false
//Set the invincible time accumulator
private float defendTimeVal = 3;

//Refer to the invincible animation
public GameObject defendEffectPrefab;
//Set invincibility in the Update main program:
void Update()
    { //Whether it is invincible
        if(isDefended){
            //SetActive directly manipulates the display and closing of the image
            defendEffectPrefab.SetActive(true);
            //The protection time is decremented
            defendTimeVal -= Time.deltaTime;
            //If 3 seconds of invincibility has elapsed, the animation is turned off, and the invincibility state is false
            if(defendTimeVal <= 0){
                isDefended = false;
                defendEffectPrefab.SetActive(false);
           }
       }}
}