Version Control: How?

We will use a system called Perforce to turn in homework starting soon.

We will just be using it as a way to trade files for a while. Later in the semester we will go through how to set it up with Unity projects so that you can work with a partner.

Example: Dragging in Candy Crush

collision.gameObject.GetComponent<Goomba>()

If the other GO has a Goomba component, this will get you a reference to it.

If the other GO does not have a Goomba component, this will return the special value null, which is nothingness.

So to determine whether the other GO has the script, you ask if the result is not null.

Not-nothing is something. So it must be a Goomba.

Goomba potentialGoomba = 

  collision.gameObject.GetComponent<Goomba>();

if (potentialGoomba != null)
{
   Die();
}

• a little annoying to set up
• sometimes GOs don't really need scripts and it's awkward to add them just for this

• reliable
• tells you what you probably really want to know, which is how the other object acts
• now you have a reference to the other script

Pros:

Cons:

if (potentialGoomba != null)
{
   Die();
}

Prefabs are necessary in order to spawn (create) new things during your game – enemies, bullets, etc.

Why? Because Unity needs to have a template to work from when you tell it to make something new.

Learn more about prefabs here:

Unity Manual

Unity tutorial video
 

Jason Weiman explains the 'why' as well as the 'how'

Overrides, variants, and nested prefabs

Once you have a prefab to work with, you can stamp out as many copies as you like.

There are two steps.

First, in the script that is going to spawn new objects, give yourself a [SerializeField] variable to hold a reference to the prefab.

[SerializeField]
GameObject blockPrefab;

This will usually be of type GameObject.

But later on you will sometimes find it more useful to use another type.

Then you can use Unity's Instantiate function to crank out the new objects.

Instantiate (blockPrefab);

This is the simplest version. It will make a new copy of the prefab. The new object's position will be whatever the prefab has as its position.

Instantiate (
    blockPrefab,
    position,
    rotation
);

Often you want to set the position of the new object at the moment you make it.

But this function requires you to set a rotation as well.

What to make (prefab)

Where (V3)

How to rotate it (Quaternion)

About 99% of the time you will use one of these two values for the rotation:

Quaternion.identity



transform.rotation

no rotation

use this GO's rotation

You will use these two versions of the Instantiate function about 90% of the time.

There are others that let you set the parent of the new object, or all of the above. See the documentation.

But you can do much more with that newly spawned object... if you save a reference.

Sometimes, as with bullets in Ikaruga or splats in Splatoon, you just need to crank out a bunch of objects and forget about them.

In that case you can simply do this:

Instantiate (
    splatPrefab,
    position,
    rotation
);

Other times you will want to remember the thing you instantiated.

Sometimes it is just for a moment, so you can set its properties. Other times you want to keep the reference for longer. Either way, this is how you save a reference to the new object:

Instantiate (
    thingPrefab,
    position,
    rotation
);

GameObject newThing =

Once you have the reference to the new instance, you can do anything you can do with a GameObject or its components.

newThing.transform.parent =
                     gameObject.transform;

newThing.GetComponent<Renderer>().enabled
                     = false;

Remember, your scripts are components too. Here is how to get a script component from a newly instantiated object and call a method on it.

Instantiate (...);

HomingMissile newMissile =

newMissile.SetTarget(player);

assumes the HomingMissile script has a public method called SetTarget

GameObject newMissileGO =

newMissileGO.GetComponent<HomingMissile>();