How To Make Particles Play On Impact?

Questions & Answers
1

Hello. I was wondering how would I make particles show when I hit an animal, tree, and ore. I am new to unity and want to know how to do this. If you guys could help me I would appreciate that.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Animations;
using UnityEngine.UI;

public class Player : MonoBehaviour
{
    public float maxHealth, maxThirst, maxHunger;
    public float thirstIncreaseRate, hungerIncreaseRate;
    private float health, thirst, hunger;
    public bool dead;

    public GameObject player;
 
    public float damage;
    public bool weaponEquipped;
    public bool toolEquipped;
    public static bool triggeringWithAI;
    public static GameObject triggeringAI;

    public static bool triggeringWithTree;
    public static GameObject treeObject;

    public static bool triggeringWithOre;
    public static GameObject oreObject;

    [Header("Particles")]
    public ParticleSystem animalImpact;
    public ParticleSystem treeImpact;
    public ParticleSystem oreImpact;

    [Header("UI Components")]
    public Text healthText;
    public Text thirstText;
    public Text foodText;

    public void Start()
    {
        health = maxHealth;
    }

    public void Update()
    {
        healthText.text = health.ToString();
        thirstText.text = thirst.ToString();
        foodText.text = hunger.ToString();

        if (!dead)
        {
            hunger += hungerIncreaseRate * Time.deltaTime;
            thirst += thirstIncreaseRate * Time.deltaTime;
        }

        if (thirst >= maxThirst)
            Die();
        if (hunger >= maxHunger)
            Die();

        //print(thirst);
        //print(hunger);
        //print(health);

        //detecting and killing ai
        if (triggeringWithAI == true && triggeringAI)
        {
            if (Input.GetMouseButtonDown(0))
                Attack(triggeringAI);
        }

        if (!triggeringAI)
            triggeringWithAI = false;

        //tree chopping
        if(triggeringWithTree == true && treeObject)
        {
            if (Input.GetMouseButtonDown(0))
                Attack(treeObject);
        }

        //ore mining
        if(triggeringWithOre == true && oreObject)
        {
            if (Input.GetMouseButtonDown(0))
                Attack(oreObject);
        }
    }


    // *****CHANGE IF IT DOESN'T WORK*****
    public void Attack(GameObject target)
    {
        if (target.tag == "Animal" && weaponEquipped)
        {
            Animal animal = target.GetComponent<Animal>();
            animal.health -= damage;
        }

        if (target.tag == "Tree" && weaponEquipped)
        {
            TreeChopping tree = target.GetComponent<TreeChopping>();
            tree.health -= damage;
        }

        if (target.tag == "Ore" && toolEquipped)
        {
            OreMining ore = target.GetComponent<OreMining>();
            ore.health -= damage;
        }
    }

    public void Die()
    {
        dead = true;
        Destroy(player);
        print("You died.");
    }

    public void Drink(float decreaseRate)
    {
        thirst -= decreaseRate;
    }

    public void Eat(float decreaseRate)
    {
        hunger -= decreaseRate;
    }

    public void OnTriggerStay(Collider other)
    {
        if (other.tag == "Tree")
        {
            triggeringWithTree = true;
            treeObject = other.gameObject;
        }

        if (other.tag == "Ore")
        {
            triggeringWithOre = true;
            oreObject = other.gameObject;
        }
    }

    public void OnTriggerEnter(Collider other)
    {
        if (other.tag == "Animal")
        {
            triggeringAI = other.gameObject;
            triggeringWithAI = true;
        }
    }

    public void OnTriggerExit(Collider other)
    {
        if (other.tag == "Animal")
        {
            triggeringAI = null;
            triggeringWithAI = false;
        }
    }
}
2

You could create an instance of your particle system (or even more complex gameObject with other effects, light, sound, etc) on impact. If you know the position of the hit, you can for example do

 Object.Instantiate(animalImpact, hitPosition, Quaternion.LookRotation(hitNormal), target.transform)

this will create a copy of your particle system, and parent it to the target (so it moves together with it). Set your particle system to play automatically and to destroy itself once it’s done. Or instantiate a gameObject with some kind of MaxLifetime component, that will destroy the gameObject after some time.
More advanced technique to optimize garbage allocation would be to have a pool of objects, and repurpose the effects that have finished playing, instead of destroying them.