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Implement projectiles for the player 

Your game now includes enemies, but no way to defeat them. In this tutorial, you’ll create projectiles that the player can launch at enemies.

By the end of this tutorial, you’ll be able to do the following:

Write a function to launch a projectile using Input Events.

Your game now includes enemies, but no way to defeat them. In this tutorial, you’ll create projectiles that the player can launch at enemies. Then, in the next tutorial, you’ll configure the projectiles to affect the enemy so the player can neutralize the threat and complete the game.

: For the purposes of this tutorial, we chose to use the 

 asset set, and the images used in instructions will reflect this. If you chose another asset set, the file names will be the same, but in your corresponding theme folder.

Overview

You’ve previously set up different GameObjects for this game, and now you’re going to repeat that process for a projectile that the player character throws at the enemy.

To set up the projectile, follow these instructions:

 window, within your chosen asset pack folder, navigate to 

This change will make the asset more proportional in size to the other game sprites. You can adjust this size if you’d like to!

 Unity Inspector showing import settings for a 2D sprite named “Projectile.” Texture type is Sprite (2D and UI), Sprite Mode Single, Pixels Per Unit 300, Mesh Type Tight, Pivot Center, Generate Physics Shape enabled. Advanced: sRGB on, Alpha Source “Input Texture Alpha,” Alpha Is Transparency checked, Wrap Mode Clamp, Filter Mode Bilinear. Platform settings use Max Size 2048, Format Automatic, Compression Normal Quality. A yellow swirling projectile sprite preview appears at the bottom.

window and release it to create a new GameObject.

GameObject so Unity can detect when the projectile collides with another GameObject.

In this situation, the default size of the collider is fine because all of the sprite needs to be able to collide with other GameObjects.

Unity Inspector showing a Rigidbody 2D component with the Gravity Scale property set to 0 and highlighted in red.

 Create a new script called “Projectile” and attach it to the 

The projectile should only be created when the player decides to use one. The prefab will still be available in the correct asset folder.

Create a projectile GameObject

To write the basic physics functionality for the projectile, follow these instructions:

 GameObject is instantiated, so this reference would be empty. Instead, 

 is called when a GameObject is initialized, even before the 

 function, which will ensure that the reference is in place.

 function, add an instruction to get the reference to the 

 function, create a new public function called “Launch”:

You’ll use these parameters to move the projectile’s 

 component: the higher the force value, the faster the projectile moves.

 function, add the following instruction:

 component; the calculation for this here is the 

 component, the physics engine will apply that force and direction to move the 

The projectile will affect the enemy on impact, so the code needs to detect when it collides with another GameObject.

 Add the following two instructions to the 

The first instruction prints a message to the console when the projectile collides with a GameObject, so you can identify the specific GameObject it has collided with.

 GameObject on collision. Eventually these projectiles will fix the enemy robots; you’ll add that functionality later in this tutorial.

Script the basic projectile functionality

You’ve created a basic projectile with some interim functionality, but at the moment the player character has no way to use it.

This variable is public, so you can assign any 

 Underneath the existing functions, add a new function called 

This instruction uses some new things that you haven’t encountered before:

, a Unity function that takes three parameters.

 creates a copy of that GameObject in a position defined by the second parameter, with the rotation defined by the third parameter.

 prefab is the GameObject. You’ve set the 

 component position. This is located at the base of the 

’s GameObject, but shifted towards the middle because it is multiplied by a 

 are mathematical operators that can express rotation. All you need to know here is that 

 Add the following two instructions underneath the last one:

The first instruction gets a reference to the 

GameObject instance, passing it the direction of movement (which you stored in a variable for the player character animations) and a 

 value that you have set is high because it’s expressed in 

 units. If you want to fine-tune the force of the projectile, you can create a public 

 variable and use that as the force instead.

 animation to play when the player character launches a projectile.

Write a function to launch projectiles

 function, you need to configure an input for it. You also need to assign the 

 prefab, so the player character actually has something to launch with this function.

r prefab in prefab editing mode, then select the 

Unity Inspector showing the Player Controller (Script) component. The Move Action Input Action is a 2D Vector. The following fields are set as: Speed 3, Max Health 5, Time Invincible 2, and Projectile Prefab to the Projectile prefab.

Detect input to launch a projectile

 for launching the projectile. You’ve already learned this process when setting up the Input Actions for player movement, so here’s a quick recap of the steps:

 Save your script, then return to the Inspector window in the Editor and add a new 

 key) is detected as pressed in that particular frame.

 Save your changes, return to the Unity Editor, and enter Play mode to test your changes.

 prefab is created, a collision with the 

 GameObject is destroyed. You could remove the destroy functionality to test this, but this change wouldn’t resolve the issue of an immediate collusion.

Define the Launch Input Action

You can address the immediate collision issue by using layers. 

 group GameObjects together so you can filter them. Here, you’ll create one layer for the player character and one layer for all projectiles. You can then instruct the physics system that these two layers can’t collide, so it ignores all collisions between objects in those layers.

To configure the player character and projectile layers for your game, follow these instructions:

window, under the GameObject header, open the 

 layer (layer 0); you can create up to 32 layers for your game. There are some built-in layers already defined.

 and call them “Character”, and “Projectiles” respectively.

: Some layers are used by Unity for fixed purposes, but you can use the other layers as needed.

, then save your changes and exit prefab editing mode.

 Repeat this process to set the correct layer for the 

Configure Layers to fix the collision issue

The final thing that you need to do is to configure your project so that the two new layers can’t collide. Layers are a helpful way to organize the different things in your game for a number of reasons. Here, layers are useful because you can turn off collisions between just the two new layers. Everything else will work as expected, but the projectile and the player character will never collide, which means that the projectile will be available for the player to launch at enemies.

To adjust the layer collision in your project, follow these instructions:

 Unity Project Settings window open to Physics 2D. The Layer Collision Matrix is highlighted in red and shows checkboxes for every layer interaction between Default, TransparentFX, Ignore Raycast, NPC, Water, UI, Character, and Projectiles. Buttons for Disable All and Enable All appear below.

By default, GameObjects in each layer can collide with GameObjects in every other layer.

Close-up of Unity Physics 2D Layer Collision Matrix highlighting in red Character and Projectiles rows. The checkbox for Character colliding with Projectiles is unchecked; the Projectiles self-collision box is unchecked.]

 Save your changes, then test the game in Play mode.

Now projectiles won’t collide with the player character, but they will collide with all other GameObjects in the scene that have colliders when you launch them.

Adjust the Layer Collision Matrix

Take a moment to check that your scripts are correct before continuing.

: If you completed any extension work in your script beyond exposing the variable that controls movement speed, this will not be reflected in the reference script below.

Check your scripts

Now that you’ve created projectiles for the player character, you can add functionality so that they actually do something to the enemy. In the next tutorial, you’ll configure the projectiles to stop enemies’ aggressive behavior.

Unity Version 6.3