As a gamer I'd phrase it like this: An AOE-Stun that stuns everyone it hits and then disappears.
I have enemy objects with a class "EnemyMovement" attached to it. This class contains a function "Slow". I have a circle that has the class "StunSpell" attached to it. Now I want to call "Slow" once for every enemy object that collides with it.
void OnTriggerStay2D(Collider2D other){
if (other.gameObject.tag == "Enemy") { //Here i want to find every gameobject (by tag "Enemy")
other.GetComponent<EnemyMovement> ().Slow (3, 0f); //Call this function once per gameobject
//And as soon as every object that was found executed "Slow" once:
// -> Destroy(gameObject); to destroy the AOE-Object
}
}
This QA is a bit messy, but it's totally normal and commonplace in video games to simply ...
private void GrenadeTimer()
{
rb.isKinematic = true;
// here is our small explosion...
Gp.explosions.MakeExplosion("explosionA",transform.position);
float radius = splashMeasuredInEnemyHeight *
Gp.markers.GeneralExampleEnemyWidth();
List<Enemy> hits = new List<Enemy>();
foreach(Enemy e in Gp.enemies.all)
{
if (e.gameObject.layer != Grid.layerEnemies) continue;
if ( transform.DistanceTo(e) < radius ) hits.Add(e);
}
hits.SortByDistanceFrom( this.transform );
boss.SequentialHits(hits,damage);
boss.Done(this);
}
It's hard to imagine anything being simpler than that.
Note that we decide on a
radius
in meters, let's say "4.2 meters", inside which we want to do damage to the enemies. (Or, buff them, or whatever the case may be.)
This thing
Gp.enemies.all
is a List<Enemy> ... it holds all the enemies in the game at the moment. Simple right?
If you do not actually have a List<> of all the enemies (or players, NPCs - whatever is relevant) - you are ###ed. Start over on your learning project. Once you have a live List which is unit-tested, come back to this.
This line of code
Grid.layerEnemies
relates to the layer system in Unity. This often causes new hobbyists a problem ...
It is beyond the scope of this article to get you started on using Layers, so we'll leave that aside. If you prefer, just leave out the line of code in your learning project.
Next. So - we run through and find all the enemies we want to affect. Let us say there are fifteen of them.
Notice that ...
By all means, when you're just learning, you can simply apply the buff/damage/etc insinde the loop:
foreach(Enemy e in Gp.enemies.all)
{
if (e.gameObject.layer != Grid.layerEnemies) continue;
if ( transform.DistanceTo(e) < radius )
e.Slow(3f, 0f);
}
However, in any real game, you have to first make a list of the items, and then most typically have a manager (let's say, your "explosions manager!" - whatever) process those hits/ buffs/ damages/ whatever.
The reason is that you can rarely just throw in happenings all in the same frame. Imagine the sound/ visual effects when I quickly explode say fifteen enemies. Almost certainly your creative director / whoever will want them to happen "rat-a-tat-tat" you know? One way or another it will be far more complex than just "triggering them all". (Also, performance-wise you may well have to stagger them - obviously this can be a huge issue involving massive code bases; don't eve mention if the game is networked.) Note that in the actual example given, they end up being staggered, and indeed by distance outwards from the grenade, which looks great.
(As a curiosity, that particular code has been used to explode on the order of one billion grenades!)
Next issue:
looking at your code, you just "GetComponent". The other objects are "dumb". In reality you never do this. Note that in the example code here, there is an actual c# class Enemy
I will paste in some of Enemy at the bottom to give a flavour.
(If you do need to get to the GameObject, say to Destroy it, you just enemy.gameObject.)
So here, since we're simply checking the distance, you immediately have the Enemy class. (If you're using physics, you have to "GetComponent" to get to the Enemy class; of course you often do that, also.)
That being said. My discussion is a bit slippery, there's an "Enemy" class (and indeed there's specific classes for enemies, such as "Dinosaur", "KillerRobot", "AttackParrot" and so on).
Try to bear in mind though, you really need to thing "behaviour-wise" in Unity.
There really shouldn't be an "AttackParrot" class. Really, there should just be components - behaviors - such as
Conceptually an "AttackParrot" would just be a game object, which, happens to have, all of those six behaviors. In contrast, it would not have say "BreathesFire" and "CanHyperjump".
This is all discussed at length here:
https://stackoverflow.com/a/37243035/294884
It's a bit "purist" to say "Oh, there shouldn't be an 'Enemy' class, only behaviors" - but something to bear in mind.
Next up,
Unity simply forgot to do this (they'll add it in the future).
Fortunately it's incredibly easy to do. Notice in the above there's a "boss" general component and a "soundEffects" general component which are called to.
In any script in your project that needs to use the general "boss" component or the general "sound" component, it's just...
Boss boss = Object.FindObjectOfType<Boss>();
Sound sound = Object.FindObjectOfType<Sound>();
That's all there is to it...
This has been explained at vast length so many times, we need only link to it:
https://stackoverflow.com/a/35891919/294884
Note that, if you prefer, the alternate way to do this using PhysX is:
If you want, take a couple of days out to master that.
Note that the examples here are for a 2D game, it's identical in 3D.
(When you measure "distance" in 3D, if you game happens only on a flat surface, you may want to bother only measuring the distance on those two axis - but honestly it's irrelevant.)
You may ask, what is SortByDistanceFrom?
To save you typing, here is that extension:
public static void SortByDistanceFrom<T>(
this List<T> things, Transform t) where T:Component
{
Vector3 p = t.position;
things.Sort(delegate(T a, T b)
{
return Vector2.Distance(p, a.transform.position)
.CompareTo(Vector2.Distance(p, b.transform.position));
});
}
This raises another issue for new hobbyists.
Example - the Enemy class mentioned above ... included to add background.
So, all the actual enemy components (Dinosaurs, Wombats, XFighters, whatever) would derive from this one, overriding (concepts like motion, etc) as appropriate.
using UnityEngine;
using System.Collections;
public class Enemy:BaseFrite
{
public tk2dSpriteAnimator animMain;
public string usualAnimName;
[System.NonSerialized] public Enemies boss;
[Header("For this particular enemy class...")]
public float typeSpeedFactor;
public int typeStrength;
public int value;
// could be changed at any time during existence of an item
[System.NonSerialized] public FourLimits offscreen; // must be set by our boss
[System.NonSerialized] public int hitCount; // that's ATOMIC through all integers
[System.NonSerialized] public int strength; // just as atomic!
[System.NonSerialized] public float beginsOnRight;
private bool inPlay; // ie, not still in runup
void Awake()
{
boss = Gp.enemies;
}
void Start()
{
}
public void ChangeClipTo(string clipName)
{
if (animMain == null)
{
return;
}
animMain.StopAndResetFrame();
animMain.Play(clipName);
}
public virtual void ResetAndBegin() // call from the boss, to kick-off sprite
{
hitCount = 0;
strength = typeStrength;
beginsOnRight = Gp.markers.HitsBeginOnRight();
Prepare();
Gp.run.runLevel.EnemyAvailable();
}
protected virtual void Prepare() // write it for this type of sprite
{
ChangeClipTo(bn);
// so, for the most basic enemy, you just do that
// for other enemy, that will be custom (example, swap damage sprites, etc)
}
void OnTriggerEnter2D(Collider2D c)
{
GameObject cgo = c.gameObject;
// huge amount of code like this .......
if (cgo.layer == Grid.layerPeeps) // we ran in to a "Peep"
{
Projectile p = c.GetComponent<Projectile>();
if (p == null)
{
Debug.Log("WOE!!! " +cgo.name);
return;
}
int damageNow = p.damage;
Hit(damageNow);
return;
}
}
public void _stepHit()
{
if ( transform.position.x > beginsOnRight ) return;
++hitCount;
--strength;
ChangeAnimationsBasedOnHitCountIncrease();
// derived classes write that one.
// todo, actually should the next passage only be after all the steps?
// is after all value is deducted? (just as with the _bashSound)...
if (strength==0) // enemy done for!
{
Gp.coins.CreateCoinBunch(value, transform.position);
FinalEffect();
if ( Gp.skillsTest.on )
{
Gp.skillsTest.EnemyGottedInSkillsTest(gameObject);
boss.Done(this);
return;
}
Grid.pops.GotEnemy(Gp.run.RunDistance); // basically re meters/achvmts
EnemyDestroyedTypeSpecificStatsEtc(); // basically re achvments
Gp.run.runLevel.EnemyGotted(); // basically run/level stats
boss.Done(this); // basically removes it
}
}
protected virtual void EnemyDestroyedTypeSpecificStatsEtc()
{
// you would use this in derives, to mark/etc class specifics
// most typically to alert achievements system if the enemy type needs to.
}
private void _bashSound()
{
if (Gp.bil.ExplodishWeapon)
Grid.sfx.Play("Hit_Enemy_Explosive_A", "Hit_Enemy_Explosive_B");
else
Grid.sfx.Play("Hit_Enemy_Non_Explosive_A", "Hit_Enemy_Non_Explosive_B");
}
public void Hit(int n) // note that hitCount is atomic - hence strength, too
{
for (int i=1; i<=n; ++i) _stepHit();
if (strength > 0) // bil hit the enemy, but enemy is still going.
_bashSound();
}
protected virtual void ChangeAnimationsBasedOnHitCountIncrease()
{
// you may prefer to look at either "strength" or "hitCount"
}
protected virtual void FinalEffect()
{
// so, for most derived it is this standard explosion...
Gp.explosions.MakeExplosion("explosionC", transform.position);
}
public void Update()
{
if (!holdMovement) Movement();
// note don't forget Translate is in Space.Self,
// so you are already heading transform.right - cool.
if (offscreen.Outside(transform))
{
if (inPlay)
{
boss.Done(this);
return;
}
}
else
{
inPlay = true;
}
}
protected virtual void Movement() // override for parabolas, etc etc
{
transform.Translate( -Time.deltaTime * mpsNow * typeSpeedFactor, 0f, 0f, Space.Self );
}
}
So that's a general enemy class. Then you have derives of that, such as Ufo, Dinosaur, Tank, XWingFighter, etc etc. Here's Ufo ...
Note that it overrides many things. It seems to override "Prepare" (the comments suggest it "starts higher", and you can see it overrides other things.
using UnityEngine;
using System.Collections;
public class Ufo:Enemy
{
public Transform projectilePosition;
protected override void Prepare()
{
// ufo always start up high (and then zip up and down)
transform.ForceY(Gp.markers.StartHeightHighArea());
animMain.StopAndResetFrame();
animMain.Play(bn + "A");
animMain.StopAndResetFrame();
Invoke("ZipDown", Random.Range(0.6f,0.8f));
}
protected override void OnGamePause()
{
CancelInvoke();
StopAllCoroutines();
}
protected override void OnGameUnpause()
{
Attack();
if(transform.position.y<0f)
ZipUp();
else
ZipDown();
}
private float fZip = 3.3f;
private void ZipDown() { StartCoroutine(_zipdown()); }
private void ZipUp() { StartCoroutine(_zipup()); }
private IEnumerator _zipdown()
{
Grid.sfx.Play("Enemy_UFO_Move_Down");
float tLow = Gp.markers.StartHeightLowArea();
while (transform.position.y > tLow)
{
transform.Translate(0f,
fZip * -Time.deltaTime * mpsNow, 0f,Space.Self );
yield return null;
}
Attack();
Invoke("ZipUp", Random.Range(0.7f,1.4f));
}
private IEnumerator _zipup()
{
Grid.sfx.Play("Enemy_UFO_Move_Up");
float tHigh = Gp.markers.StartHeightHighArea();
while (transform.position.y < tHigh)
{
transform.Translate(0f,
fZip * Time.deltaTime * mpsNow, 0f,Space.Self );
yield return null;
}
Attack();
Invoke("ZipDown", Random.Range(0.7f,1.4f));
}
private void Attack()
{
Grid.sfx.Play("Enemy_UFO_Shoot");
animMain.Play();
Invoke("_syncShoot", .1f);
}
private void _syncShoot()
{
Gp.eeps.MakeEepUfo(projectilePosition.position);
}
protected override void ChangeAnimationsBasedOnHitCountIncrease()
{
// ufo just goes 4,2,out
if (strength == 2)
{
// if any attack, cancel it
CancelInvoke("ShootGreenPea");
CancelInvoke("Attack");
// on the ufo, anim only plays with attack
animMain.StopAndResetFrame();
animMain.Play(bn + "B");
animMain.StopAndResetFrame();
Invoke("Attack", 1.5f.Jiggle());
}
}
protected override void EnemyDestroyedTypeSpecificStatsEtc()
{
Grid.pops.AddToEnemyCount("ufo");
}
}
Let's think about the idea of "overrides in the Enemy class".
The many enemies have different types of movement, right? The general paradigm in the game is things moving in 2D, kinematically (ie, we "move them a certain amount of distance each frame" - not using PhysX here). So the different enemies move in radically different ways.
Here's one that moves in a certain way ... (the comments explain it)
protected override void Movement()
{
// it enters at about 2x normal speed
// the slow crossing of the stage is then about 1/2 normal speed
float mpsUse = transform.position.x < changeoverX ? mpsNow*.5f : mpsNow * 2.5f;
transform.Translate( -Time.deltaTime * mpsUse * typeSpeedFactor, 0f, 0f, Space.Self );
// recall that mpsNow was set by enemies when this was created, indeed
// nu.mpsNow = ordinaryMps * widthSpeedFactor;
}
Here's one that goes along, but sometimes "drifts downwards..."
protected override void Movement()
{
float mm = mpsNow * typeSpeedFactor;
if ( fallingMotion )
transform.Translate(
-Time.deltaTime * mm,
-Time.deltaTime * mm * fallingness, 0f,
Space.Self );
else
transform.Translate(
-Time.deltaTime * mm, 0f, 0f,
Space.Self );
}
Here's one that seems to follow a sinus ...
protected override void Movement()
{
transform.Translate( -Time.deltaTime * mpsNow * typeSpeedFactor, 0f, 0f, Space.Self );
float y = Mathf.Sin( basis-transform.position.x * (2f/length) );
y *= height;
transform.transform.ForceY( y );
}
Here's one that does complex speed changes, zooming around
protected override void Movement()
{
// it enters at about 2x normal speed
// it appears to then slow crossing of the stage about 1/2 normal speed
// however it then zooms to about 3x normal speed
float mpsUse = mpsNow;
float angled = 0f;
if ( transform.position.x > changeoverX) //enter quickly
mpsUse = mpsNow * 3f;
if ( transform.position.x < thenAngled) // for bead, angled section
{
mpsUse = mpsNow * 1.5f;
angled = leanVariation;
}
transform.Translate(
-Time.deltaTime * mpsUse * typeSpeedFactor,
-Time.deltaTime * mpsUse * typeSpeedFactor * angled,
0f, Space.Self );
}
You could make the movement anything - flying, running, bouncing, whatever.
It's all handled in c# by the protected override concept.
Here's a trivial example of a static class which holds what you might as well call "globals", In a game engineering milieu, it's sensible to have certain things as "globals".
using UnityEngine;
using Shex;
using System.Collections;
using System.Collections.Generic;
static class Gp
{
public static Enemies enemies;
public static Pickups pickups;
public static Coins coins;
public static Peeps peeps;
public static Eeps eeps;
}
So TBC complicated "general" systems like SoundEffects, Boss, Scoring, AI, Networking, Social, InAppPurchase etc etc as described above, would indeed by the "preload" type objects as explained. (ie, you're using Boss boss = Object.FindObjectOfType(); at the top of any script, in any scene etc, that needs them.)
But for simply variables, things, that just need to access everywhere, you can use a trivial static class like that. Often just the one static class (called something like "Gameplay" or "Gp") does the job for the whole project.
{By all means, some teams would say "screw that, don't use a static class, put it in a "general" ("preload-style") component like Boss...."}
Note that of course a static class is NOT a real MonoBehavior - you "can NOT actually "DO" anything inside it in Unity". It's only for "holding variables" (most often, Lists) you want to access easily everywhere.
Again, be sure to remember that a static class is quite simply NOT a Unity game object or component - hence it very literally is not part of your game; you literally can not "do" anything whatsoever in a static class. To "do" anything, at all, in Unity it must be an actual Component, literally on a specific GameObject, at some position.
Thus for example it's completely useless trying to keep your "score" in a simple static class. Inevitably in relation to the "score" you will want to do all sorts of things (change the display on screen, award points, save encrypted preferences, trigger levels ... whatever, there is a lot of stuff to do). You absolutely cannot do that in a static - you can not "do" anything, at all, in a static - it must be an actual Unity game object. (ie, using the "preload system".) Once again statics are just for literally keeping track of some basically "global" variables, usually lists of things. (Things like "screen markers" are the perfect example.)
Just BTW in game development an "eep" is an enemy projectile and a "peep" is a player projectile, heh!