Collectables

In Zelda, a huge part of the project is maintaining an inventory. Thankfully for us, Metroid doesn’t have all this work (we did have to spend a lot of extra time on physics though).

In this final section, we’re going to implement the Morph Ball and implement a simple inventory.

Creating the Pickup

Create a new GameObject named Morph Ball.

Make it a Child of RoomA (remember, we want our Collectables and Enemies to be children of Rooms so they’re disabled with them).

Set the Local Position to (46, 2, 0). This isn’t the actual position of the collectable, but a moving Camera isn’t part of this tutorial so you wouldn’t be able to see it in its real position.

Add a SpriteRenderer with Sprite: metroid_samusaran_sheet_3

Hey, this isn't the right sprite. What's the deal?

You've got a keen eye. The real MorphBall flickers between two vibrantly colored sprites.

As with all of the Assets you'll now need, it's up to you to find these correct sprites on your own!

Add a SphereCollider with Radius: .5 and IsTrigger: True.

We don’t need to worry about a Rigidbody since this will never move!

The last thing we need to do is give the Game Object a Tag so the Player can check to identify the Trigger.

Couldn't I just check the object by name? Why do I need a tag?

Names can be messed up by Unity in some cases. Instantiating a new object will append "(Clone)" to the end, and duplicating an object will append a number to the end. Tags don't have this problem.

Go to the Tags & Layer Manager under Edit->Project Settings->Tags and Layer. Add a new Tag named MorphBall.

NewTag

Give this tag to your MorphBall GameObject.

Pickup

That’s it! Our Player will handle the rest of the logic for picking this up. Convert this to a Prefab by dragging the object from the Inspector into the Prefabs folder.

There's only ever going to be one Morph Ball. Why do I still need to make it a prefab?

As I said with the Player prefab, you may decide you want to use the Morph Ball in different scenes (Either your custom level or any test scenes).

Plus it will be good to have all of your Collectables in one spot to change them without finding them in your scene.

PlayerInventory

Now let’s create a simple script to manage the Player’s Inventory. Create a script named PlayerInventory.cs in the Scripts folder and attach it to the Player Object.

Create a public bool to keep track of if the player has a morph ball.

Script1

Won't I need other variables for the other resources?

Yep! But you can add these later once you start working on the other Collectables.

Why is the hasMorphBall variable public instead of private?

Good question! It would seem like the Morph Ball should always default to false so it shouldn't need to be set in the inspector.

As you're building your project, you might find it a pain to pick up the Morph Ball every playthrough. Instead, you can just turn this on in the inspector and you won't have to waste your time grabbing it. Just make sure to turn it off before your builds though.

An even better solution would be to make a Cheat Manager that turns this on, and you may consider this when you implement the other cheats we require.

Now we need to check for the Player’s Collision with the MorphBall. In an OnTriggerEnter() function, check the Collider’s Tag. If it matches “MorphBall” destroy the object and set hasMorphBall to True.

Script2

Unfortunately, we aren’t picking up the ball just yet. Bugs like this are super frequent with Beginner Unity development. Did we set the Tag wrong? Is our syntax for OnTriggerEnter() bad? Did we set up the Colliders correctly?

In this case, OnTriggerEnter() is never being called. This is because our Player object doesn’t have a Collider, the Children have the Colliders.

So we need to call the Parent OnTriggerEnter() whenever the Child OnTriggerEnter is called.

First expose the OnTriggerEnter call by making it public.

Script3

Create a new script PassUpTriggerEnterToInventory.cs in the Scripts folder and attach it to both Standing and Morphed.

In this script you should first store a reference to the PlayerInventory. Then pass up the Collider when this object hits a trigger.

Script4

Restricting State Changes

The last thing we need to do is have the PlayerState script check the inventory before it lets the Player morph.

First let’s add a Getter in PlayerInventory.cs for if the player has the MorphBall.

Getter

But hasMorphBall is already public, why should I make a Getter function?

While this variable is public to make it easier to debug, we should still apply good coding practices and assume it's private.

Now in PlayerState.cs store a reference to the inventory and check the playerInventory before allowing a morph.

CheckInventory

Conclusion

You’ve made it! You are now officially done with the Metroid tutorials. Don’t celebrate too much though as you still have a lot of work ahead of you.

Final

When you’re ready, commit your changes and head over to 13: Next Steps.