Creating and Firing Shells

Phase 5 teaches you how to create a Shell for the tank, creating a radius for explosion.

ShellExplosion Script

using UnityEngine;

public class ShellExplosion : MonoBehaviour
{
    public LayerMask m_TankMask;                        // Used to filter what the explosion affects, this should be set to "Players".
    public ParticleSystem m_ExplosionParticles;         // Reference to the particles that will play on explosion.
    public AudioSource m_ExplosionAudio;                // Reference to the audio that will play on explosion.
    public float m_MaxDamage = 100f;                    // The amount of damage done if the explosion is centred on a tank.
    public float m_ExplosionForce = 1000f;              // The amount of force added to a tank at the centre of the explosion.
    public float m_MaxLifeTime = 2f;                    // The time in seconds before the shell is removed.
    public float m_ExplosionRadius = 5f;                // The maximum distance away from the explosion tanks can be and are still affected.


    private void Start ()
    {
        // If it isn't destroyed by then, destroy the shell after it's lifetime.
        Destroy (gameObject, m_MaxLifeTime);
    }


    private void OnTriggerEnter (Collider other)
    {
        // Collect all the colliders in a sphere from the shell's current position to a radius of the explosion radius.
        Collider[] colliders = Physics.OverlapSphere (transform.position, m_ExplosionRadius, m_TankMask);

        // Go through all the colliders...
        for (int i = 0; i < colliders.Length; i++)
        {
            // ... and find their rigidbody.
            Rigidbody targetRigidbody = colliders[i].GetComponent<Rigidbody> ();

            // If they don't have a rigidbody, go on to the next collider.
            if (!targetRigidbody)
                continue;

            // Add an explosion force.
            targetRigidbody.AddExplosionForce (m_ExplosionForce, transform.position, m_ExplosionRadius);

            // Find the TankHealth script associated with the rigidbody.
            TankHealth targetHealth = targetRigidbody.GetComponent<TankHealth> ();

            // If there is no TankHealth script attached to the gameobject, go on to the next collider.
            if (!targetHealth)
                continue;

            // Calculate the amount of damage the target should take based on it's distance from the shell.
            float damage = CalculateDamage (targetRigidbody.position);

            // Deal this damage to the tank.
            targetHealth.TakeDamage (damage);
        }

        // Unparent the particles from the shell.
        m_ExplosionParticles.transform.parent = null;

        // Play the particle system.
        m_ExplosionParticles.Play();

        // Play the explosion sound effect.
        m_ExplosionAudio.Play();

        // Once the particles have finished, destroy the gameobject they are on.
        Destroy (m_ExplosionParticles.gameObject, m_ExplosionParticles.duration);

        // Destroy the shell.
        Destroy (gameObject);
    }


    private float CalculateDamage (Vector3 targetPosition)
    {
        // Create a vector from the shell to the target.
        Vector3 explosionToTarget = targetPosition - transform.position;

        // Calculate the distance from the shell to the target.
        float explosionDistance = explosionToTarget.magnitude;

        // Calculate the proportion of the maximum distance (the explosionRadius) the target is away.
        float relativeDistance = (m_ExplosionRadius - explosionDistance) / m_ExplosionRadius;

        // Calculate damage as this proportion of the maximum possible damage.
        float damage = relativeDistance * m_MaxDamage;

        // Make sure that the minimum damage is always 0.
        damage = Mathf.Max (0f, damage);

        return damage;
    }
}

Phase 6 teaches you how to fire projectiles, and make a UI & Sound fx to accompany the mechanic.

TankShooting Script

using UnityEngine;
using UnityEngine.UI;

public class TankShooting : MonoBehaviour
{
    public int m_PlayerNumber = 1;              // Used to identify the different players.
    public Rigidbody m_Shell;                   // Prefab of the shell.
    public Transform m_FireTransform;           // A child of the tank where the shells are spawned.
    public Slider m_AimSlider;                  // A child of the tank that displays the current launch force.
    public AudioSource m_ShootingAudio;         // Reference to the audio source used to play the shooting audio. NB: different to the movement audio source.
    public AudioClip m_ChargingClip;            // Audio that plays when each shot is charging up.
    public AudioClip m_FireClip;                // Audio that plays when each shot is fired.
    public float m_MinLaunchForce = 15f;        // The force given to the shell if the fire button is not held.
    public float m_MaxLaunchForce = 30f;        // The force given to the shell if the fire button is held for the max charge time.
    public float m_MaxChargeTime = 0.75f;       // How long the shell can charge for before it is fired at max force.


    private string m_FireButton;                // The input axis that is used for launching shells.
    private float m_CurrentLaunchForce;         // The force that will be given to the shell when the fire button is released.
    private float m_ChargeSpeed;                // How fast the launch force increases, based on the max charge time.
    private bool m_Fired;                       // Whether or not the shell has been launched with this button press.


    private void OnEnable()
    {
        // When the tank is turned on, reset the launch force and the UI
        m_CurrentLaunchForce = m_MinLaunchForce;
        m_AimSlider.value = m_MinLaunchForce;
    }


    private void Start ()
    {
        // The fire axis is based on the player number.
        m_FireButton = "Fire" + m_PlayerNumber;

        // The rate that the launch force charges up is the range of possible forces by the max charge time.
        m_ChargeSpeed = (m_MaxLaunchForce - m_MinLaunchForce) / m_MaxChargeTime;
    }


    private void Update ()
    {
        // The slider should have a default value of the minimum launch force.
        m_AimSlider.value = m_MinLaunchForce;

        // If the max force has been exceeded and the shell hasn't yet been launched...
        if (m_CurrentLaunchForce >= m_MaxLaunchForce && !m_Fired)
        {
            // ... use the max force and launch the shell.
            m_CurrentLaunchForce = m_MaxLaunchForce;
            Fire ();
        }
        // Otherwise, if the fire button has just started being pressed...
        else if (Input.GetButtonDown (m_FireButton))
        {
            // ... reset the fired flag and reset the launch force.
            m_Fired = false;
            m_CurrentLaunchForce = m_MinLaunchForce;

            // Change the clip to the charging clip and start it playing.
            m_ShootingAudio.clip = m_ChargingClip;
            m_ShootingAudio.Play ();
        }
        // Otherwise, if the fire button is being held and the shell hasn't been launched yet...
        else if (Input.GetButton (m_FireButton) && !m_Fired)
        {
            // Increment the launch force and update the slider.
            m_CurrentLaunchForce += m_ChargeSpeed * Time.deltaTime;

            m_AimSlider.value = m_CurrentLaunchForce;
        }
        // Otherwise, if the fire button is released and the shell hasn't been launched yet...
        else if (Input.GetButtonUp (m_FireButton) && !m_Fired)
        {
            // ... launch the shell.
            Fire ();
        }
    }


    private void Fire ()
    {
        // Set the fired flag so only Fire is only called once.
        m_Fired = true;

        // Create an instance of the shell and store a reference to it's rigidbody.
        Rigidbody shellInstance =
            Instantiate (m_Shell, m_FireTransform.position, m_FireTransform.rotation) as Rigidbody;

        // Set the shell's velocity to the launch force in the fire position's forward direction.
        shellInstance.velocity = m_CurrentLaunchForce * m_FireTransform.forward; ;

        // Change the clip to the firing clip and play it.
        m_ShootingAudio.clip = m_FireClip;
        m_ShootingAudio.Play ();

        // Reset the launch force.  This is a precaution in case of missing button events.
        m_CurrentLaunchForce = m_MinLaunchForce;
    }
}