In this second part of the Introduction to Unity tutorial you’ll learn: “How to use the Project window to import and organize your assets”, “The difference between GameObjects and Prefabs”, “How physics work in Unity”, “How cameras work and which types of projections are available” and “The basics of Materials in Unity”.
In Part 1 of this Introduction to Unity tutorial series, you’ve learned the ins-and-outs of the Unity interface. In this second part, you’ll work in the Unity interface as you create your first game, a small space shooter. Along the way, you’ll learn:
- How to use the Project window to import and organize your assets.
- The difference between GameObjects and Prefabs.
- How physics works.
- How cameras work and types of projections that are available.
- The basics of materials.
This tutorial will give you an overview of Unity’s various systems, and you’ll assemble a game from pre-created assets. In subsequent tutorials, you’ll learn about Unity’s subsystems in depth while you create your own assets and write your own scripts. When you’re finished, the result will look like this:
There’s a lot to cover, so put your phone on airplane mode, lock the doors, and open your mind to the world of Unity!
You can find the link to the Download Materials at the top or bottom of this tutorial.
They contain four folders:
- game assets
- starter project
- final project
You can use the project that you worked on in the first part of the tutorial, or you can open the starter project in Unity using File ► Open Project and then selecting the Space Debris Starter project folder.
In your file system, navigate to the game assets folder from the collection of sample files, select all files in that folder, and drag them into the Assets folder in the Project window in Unity.
When Unity has finished importing the files, your Project window will look like the following:
Unity defaults to large thumbnails, but if you prefer to work with lists instead, you can change it like this: At the bottom of the Project window, move the slider to the left to shrink the assets thumbnails.
While keeping all your assets in one folder is convenient, it’s disorganized. It doesn’t seem like a big problem when you first start a project, but as your project expands, so will your collection of assets.
By organizing your assets up front, you’ll spend less time searching for them and more time actually building your game.
Your next step is to organize your assets into folders. In the Project window, click the Create button and select Folder from the list of options.
Name the new folder Materials. Your Project window should now look like the following:
Now create the following five folders to hold the rest of your assets:
Folders in Unity behave much like the ones on your computer. You can create subfolders and drag folders in and out of other folders. The underlying filesystem will match the organization in Unity, which makes it easy for you to find your assets outside of Unity.
Now, it’s time to get organized!
Select the Bullet, Debris, GameManager, IonCannon, RendererFade, ScreenWrap and ShipController scripts and drag them into the Scripts folder.
At the end of the day, it’s a script like any other. The icon just helps you recognize it since you’ll access it often. There are special icons for other components as well. You’ll discover these as you dig deeper into Unity.
Next, select the background-music, explosion and shoot sound files and drag them into the Sounds folder.
Finally, select the flint_like_rock_4787 texture and move it into the Textures folder.
Your Project window should now look like the following:
At this point, you’re probably eager to start making your game. But before you get too far, you need to get into the habit of saving your work since Unity doesn’t offer an autosave feature. If Unity crashes or you lose your power, you’d lose everything except your project organization.
Unity saves your work in scenes. A scene can be one level of many in a game, or it could be the only level in the entire game. In this tutorial, you’ll use just one scene for everything.
Press Command-S (Ctrl-S on Windows) to save your game. A save dialog will open. Name your scene Main.
Create Your First Instance
What’s a game without a player? Look inside models / player from the sample files you downloaded earlier. You’ll see an FBX file along with a few image files.
An FBX file contains all the data required to create a 3D model, along with other things such as animations. The player file you’ll use in this Unity tutorial was created by ComboMash for his game Hextraction.
Select all the files in the player folder and drag them on top of the Assets folder in your Project window. You’ll see the following dialog:
Some image files convey extra information for Unity, but are saved in standard image format. In this case, p_pod_normal.jpg defines the depths of a surface, which provides surface lighting information without the need to create additional geometry. This is called a normal map.
However, Unity thinks it’s dealing with a regular image. Click Fix now to instruct Unity to treat this file as a normal map.
By default, Unity will import cameras with your model. For this game, you need only one camera: the main camera. Select the hextraction_pod in the Project window. In the Inspector window, make sure the Model tab is selected. Uncheck Import Cameras.
With that complete, click the Apply button.
With player files imported, drag the hextraction_pod asset from the Project window into the Scene view.
Cool – you’ve created your first instance of a model. Unity correctly imported the textures and applied them to the model.
You’ll also notice the Hierarchy now lists the new GameObject.
Working with GameObjects
As noted in Part 1 of this tutorial series, everything in your Hierarchy will be a type of GameObject. A GameObject by itself contains what’s known as a transform, which has information about the position, scale, and rotation of the GameObject.
You customize GameObjects by adding Components to them. You can think of components as representing the behavior and appearance of the GameObject.
For instance, you can add a lighting component to illuminate your GameObject. You can add an Audio Source to make your GameObject emit sound. Or you can even write your own components as scripts and attach them to GameObjects.
GameObjects can also act as containers. Hold down the Alt key and click on the disclosure triangle to the left of hextraction_pod in the Hierarchy. This will expand the GameObject and all levels below it. You’ll see the following collection of GameObjects:
A lot of these are empty GameObjects that represent the structure of a model. Unity creates these GameObjects when you import a model. Other GameObjects, such as the children of pod_mesh, contain components such Skinned Mesh Renderers to display geometry on the screen.
You’ll notice that some GameObjects in the Hierarchy are labeled in black, while others are labeled in blue.
The black color means it’s a standard GameObject. The blue text tells you the GameObject is an instance of a model or if it’s connected to other objects with a Prefab. Sometimes GameObjects also turn brown. This means they’ve lost the prefab connection.
You can tell that you have an instance of a model by its icon.
Working with Prefabs
Generally, you don’t want to use model instances. It’s better to use prefabs. Prefabs let you save GameObjects so they’re easily duplicated either using code or through dragging new instances into the Scene view.
Prefabs are a bit like using sand forms. Except, the instances of the Prefab are all connected. When you change the Prefab, the instances will change as well.
Once you have an instance of a Prefab in the Scene view, you can customize it as you like. There may be times when you want to push these changes to existing Prefabs (because you liked them) or reset the instance to the state of the original prefab (because you messed up).
To create a Prefab, you drag a GameObject from the Hierarchy and into the Project window.
When you do this, you’ll get a dialog that asks whether you want to create a new prefab or a variant of a prefab.
Since you don’t have a prefab, click the Original Prefab button.
You’ll notice that your icon will turn completely blue. This means you’re working with a prefab instance.
Select hextraction_pod from the Hierarchy. In the Inspector window you’ll see two buttons: Open and Select. There’s also a dropdown called Overrides:
Open allows you to open the prefab and edit it. This allows you to focus on just the prefab. The Hierarchy will only show the selected prefab. To return back to normal editing, click the back arrow in the Hierarchy.
Select locates the Prefab in your Project window. This is particularly useful when you misplace your Prefab in a complicated folder structure within your Project window. Try it now to see what happens.
When you make changes to a Prefab, you’re making a change to a single instance of the Prefab. In Unity-speak, you’re overriding parts of the Prefab. You can apply these changes to the other Prefabs, Revert the changes, or you can just leave them as is. This is done by pressing the Overrides dropdown.
Currently, the player’s ship has a tiled grid underneath it, which looks a bit strange. First, you need to edit the prefab.
Select the prefab and in the Inspector window, click the Open button. Then, select the tile_reference GameObject from the Hierarchy. This is a direct child of the hextraction_pod GameObject.
Delete the grid by pressing the Delete key on Windows or Cmd-Delete on macOS. Click the back arrow in the Hierarchy to exit Prefab editing.
You’ll be prompted to save your changes as you exit Prefab mode. Click Save.
Next, right click on hextraction_pod in the Hierarchy window, select Rename from the drop down menu that appears, and rename the GameObject to Spaceship. It should look like the following:
Dragging a GameObject into the Project window converts it into a prefab without any extra effort on your part. You could create as many instances of the Spaceship as you want by dragging them from the Project window into the Scene view.
Currently, this only copies the model, but later it could contain scripts, audio settings, and much more. As you can see, Prefabs can be really helpful.
Controlling the Camera
A spaceship isn’t really useful if it can’t move. In this section, you’ll give the player control of the spaceship.
To do that, you’ll need to deal with two things: The camera and the physics system. Don’t worry, you won’t need to learn subatomic particle physics today! :]
First, you need to set up the ship.
- Select the Spaceship in the Hierarchy window.
- Use the Inspector window to set its Position to (X:10.66, Y:1.99, Z:10).
- Set the Rotation to (X:270, Y:0, Z:0).
The values in the Inspector window will match those shown below.
So how did I come up with these values? They are actually quite random.
As I developed the game, I placed the objects in these starting positions. If you made the game, you might have chosen different positions.
Looking at the Game view, you can see that the ship is still a little too close to the camera.
There are two ways to fix this. You can either move the ship further back, or you can reconfigure the camera. Prepare to become a camera assistant! :]
Select the Main Camera in the Hierarchy. You’ll see a Camera component in the Inspector. There are a ton of options here, but for now ignore everything except Projection and Field of View.
You can choose Perspective or Orthographic for your projection field. This choice determines the ultimate appearance of the game.
Perspective projection behaves very much like your eye does. The closer an object is to your eye, the larger it appears. Orthographic projections discard depth information. Objects closer to you, or in this case, the camera, will appear the same size as objects farther away.
Generally speaking, 3D games should use Perspective projection. Games without depth, like 2D games, should use Orthographic projection.
While your game has 3D elements, the gameplay is essentially 2D. In the Projection field, select Orthographic. Next, set the size to 18.85. Your Game view should look like the following:
A spaceship should fly, shouldn’t it? To do this, you’d have to write some code in C# to move the ship frame-by-frame. To save you some work, the example files contain a ready-to-use script. The question is, how do you add it to your ship?
A script is simply another type of component, and there are lots of ways to add components to GameObjects. You’ll experiment with a few methods in this tutorial.
For now, select Spaceship from the Hierarchy. Then select the Component option from the menu bar. At the bottom, you’ll see an option called Scripts with a flyout menu of available scripts. Select the Ship Controller script.
You should now see that the
Ship Controller script has been added as a Script component to the Spaceship GameObject in the Inspector window.
Just as with other components, you can define fields in your scripts that you can access in the editor. This gives you the ability to change properties of your scripts while your game is being played.
Set the Move Speed of your component to 22 and Rotation Speed to 2.
The move speed determines the speed of the ship, while the rotation speed determines how quickly the ship can turn. Hit the Play button in the center top of the Unity interface. This starts the game. Use the arrow keys to move your ship.
Unfortunately, your ship will fly off the screen, to Alpha Centauri and beyond. You’ll need to fix that.
Use the menu bar as before to add the Screen Wrap script to the spaceship.
You’ll notice that this component has a field named Renderers, which takes an array of Skinned Mesh Renderers. This is the geometry that creates a model.
If a renderer isn’t onscreen, then it teleports the GameObject to another position on screen based on its movement direction and current position.
Expand the Spaceship node until you find the body GameObject, then drag body into the Renderers field.
Now run your game. To infinity… and beyond! :]
Did you remember to save your work?
There’s just one major problem. In flying your ship around, you violated one of the laws of physics. No, not Newton’s laws of physics — the laws of Unity physics best-practices.
Unity uses physics for collision detection. If a GameObject doesn’t have a RigidBody component, it’s considered a static collider.
This means Unity assumes that the GameObject will stand still, which allows for huge optimizations when it comes to collision detection. But when you start moving those static objects around anyway, Unity has to recalculate those optimizations. This adds unnecessary CPU time to your game.
To avoid this unnecessary CPU overhead, you’ll need to opt-into the physics engine by adding a Rigidbody component. You’ve already added components directly from the menu bar. This time, with the Spaceship still selected in the Hierarchy, click the Add Component button in the Inspector.
You’ll see a component menu appear. Click Physics, then Rigidbody.
This component has a lot of options. Is Kinematic is the one you’re interested in.
Setting this option means that you want to move a GameObject manually, but still want the object to register for collisions. This is useful when you’re moving items via scripts, like you’re doing here, or via animation.
Tick the Is Kinematic checkbox. Since you aren’t using gravity in this game, uncheck the Use Gravity checkbox like so:
The object of this game is to fly around and shoot various types of debris. Naturally, handling collisions will play a large role in this type of game. You’ll need to know when the player shoots an asteroid or when a player crashes into something.
Colliders let you listen to and respond to collisions. There are many types of colliders to use with basic shapes, such as Sphere Collider and Box Collider.
There’s even a mesh collider that’s based on a 3D model. Colliders are displayed in the Scene view using green lines.
In this tutorial, you’ll keep things simple and use a Sphere Collider.
Select the Spaceship in the Hierarchy window and click the Add Component button in the Inspector window. Click Physics / Sphere Collider, and you’ll see a green circle behind the Spaceship.
Uh, wait — why is the collider behind the Spaceship? That’s because the actual model of the Spaceship has been offset from the parent when you changed its position earlier.
- With the Spaceship selected in the Hierarchy, find your Sphere Collider in the Inspector.
- Set Center to (X:0, Y:4.09, Z:-0.72)
- Set the Radius to 3.14
- Check the Is Trigger checkbox. Kinematic GameObjects can’t register normal collisions, but they can listen to trigger events from other kinematic objects.
Your Sphere Collider component should look like the following:
The collider should also enclose the Spaceship, like so:
Arming the Cannons
While flying around is fun and all, most players have an overarching desire to fire off a few dozen photon torpedos! :]
A script’s been provided for you to help satisfy that craving.
Select the Spaceship in the Hierarchy and click the Add Component button in the Inspector window. Click Scripts / Ion Cannon.
You’ll notice an Audio Source component was automatically added to the GameObject as well as the script.
Some scripts require components. If the components aren’t found on the GameObject, they’ll be added automatically.
To make your objects play sounds, you need both an Audio Source and an Audio Clip. An Audio Source can be attached to any GameObject, while an Audio Clip is simply an audio file.
Drag the shoot sound from the Sounds folder in the Project window into the Fire Sound field.
You’ll notice that the Ion Cannon script has a Bullet field. Your job is to create a bullet object. Don’t worry if you’re not an artist – a simple sphere will suffice.
Click the Create button in the Hierarchy. From the menu, select 3D Object, then select Sphere.
Select the Sphere in the Hierarchy, then use the Inspector to set Scale to (X:0.47, Y:0.47, Z:0.47). Select the Sphere in the Hierarchy again and name it Bullet.
Since your bullet is going to be moving across the scene, it needs to opt-into the physics engine as well. Do you remember what you need to do? Give it a whirl and if you’re stuck, check the spoiler below.
[spoiler]Select the Bullet from the Hierarchy and click the Add Component button in the Inspector. Select Physics / Rigidbody to add the Rigidbody component.[/spoiler]
The bullet will need velocity to move, so make sure Is Kinematic is unchecked. Also, make sure Use Gravity is unchecked.
The bullet will keep traveling even after it flies offscreen, just like your spaceship did originally. Drag the Bullet script from the Project window onto the Bullet GameObject. Now, when the bullet flies offscreen, it will automatically be destroyed.
Finally, drag your Bullet object into the Prefab folder of your Project window. This creates a Prefab of the bullet, which allows you to create lots of bullets using a script. Pew, pew! :]
Now that you have your bullet created as a Prefab, delete the instance of the bullet from the Hierarchy.
Select your Spaceship again, and use the Inspector to add the Bullet Prefab to the Bullet field. The Inspector should look like so:
Finally, the sky background is somewhat out of place. You’d expect a spaceship to fly in the black void of space, wouldn’t you? :]
Select Main Camera in the Hierarchy and use the Inspector to set Clear Flags to Solid Color and Background Color to black.
Save your work, run your game, and press the space bar to blast away with the Ion cannon!
Putting the Debris in Space Debris
So far you have a ship that can fire, but it would be far more interesting if there was something to shoot at. It’s time for you to add some asteroids to the mix.
Find the rock_d_05.obj file in your downloaded files and drag it into the Models folder in the Project window.
Right-click rock_d_05.obj and rename it Asteroid.
This file only contains information about the model itself. It doesn’t have any animations included.
Drag the Asteroid model into the Scene view to create an instance of it. You’ll see that the asteroid is currently plain white.
While you could make the argument that it’s a fragment of a snow-white comet, you should learn how to texture your models… unless you want to make a career of creating snow-themed games. :]
Expand the Asteroid GameObject and select its child object named rockLP001. In the Inspector, you’ll see that this child GameObject has a Mesh Renderer component attached to it. The renderer draws the object to the screen, but needs a bit of help to do this – that’s where Materials come into play.
Materials determines the appearance of your objects. For example, a cotton shirt will look much different than a plaster wall would.
Unity achieves this by encapsulating a shader with each material.
What’s a shader, you ask? It’s a simple program written in a C-like language that runs on the GPU. A shader can be simple enough to render a texture on a cube, or it can be complex enough to simulate water.
Unity provides many different shaders out of the box. For example you can use them to render a sky box, or make an object appear translucent.
Open the Materials folder in the Project window, and click the Create button. From the dropdown, select Material and give it the name Asteroid. In the Inspector window you’ll now see the available properties for a material.
- The Shader option lets you choose from one of the many pre-packaged shaders. The default Standard Shader has enormous flexibility, so leave it selected.
- When an asteroid is hit, you’ll want to fade it out, so set the Rendering Mode to Fade.
The Albedo property holds the actual texture. You can tint it by providing a color.
Drag the flint_like_rock_4787 image from the Textures folder in the Project window to the Albedo property:
Looking at the Asteroid material preview at the bottom of the Inspector window, you’ll notice the material looks a little too smooth, like it’s been polished. (If you don’t see the material preview, try dragging the Asteroid title bar up from the bottom of the Inspector like so):
Under the Metallic property, you’ll see two sliders. The first slider determines the metallic appearance of the material, while the other determines how rough the texture is.
For now, set the Metallic slider to 0.219
- Set the Smoothness slider to 0.149. Your Material should now look like this:
With the material all configured, you now need to add it to the asteroid. Drag your Asteroid material from the Project window to the Asteroid GameObject in the Scene view.
Awesome! You have an asteroid ready to cause lots of trouble. But first you need to add some behavior to it.
Drag the Debris script from the Project window in the Scripts folder to the Asteroid.
The Debris script automatically added a Sphere Collider, Rigidbody, and Audio Source to the Asteroid. Now set up all the required properties.
- Set the center of the Sphere Collider to (X:0.01, Y:-0.09, Z:0.89).
- Set the Radius to 1.49.
- Check the Is Trigger checkbox.
- For the Rigidbody, uncheck the Use Gravity checkbox.
- Check the Is Kinematic checkbox.
- For the Debris script, set Min Speed to 15.
- Set the Max Speed to 30.
- Drag the explosion sound file from the Sounds folder to the Explosion Sound field.
- For the transform of the Asteroid GameObject, set the Scale to (X:3.02, Y:3.02, Z:3.02).
- Adding the Debris component also added the required Renderer Fade component. When a bullet collides with an asteroid, the asteroid should fade away instead of simply disappearing from the screen. The component only requires a fade time, so set Fade Time to 0.5.
- Set the Min Time to 2 and the Max Time to 5. This tells the script how quickly it should spawn asteroids.
- Set Total Items on Screen to 5. This limits the number of asteroids to 5 so that the player doesn’t get overwhelmed.
- Drag the Debris GameObject from the Hierarchy to the Screen Debris field. This specifies that the GameManager should spawn asteroids on the Debris GameObject.
As asteroids drift off the screen, they should wrap just like the Spaceship.
From the Scripts folder in the Project window, drag the ScreenWrap script to the Asteroid. Just as you did with the Spaceship, you’ll need to configure the Screen Wrap with the correct renderer.
The Asteroid has a child GameObject named rockLP001. Drag this child GameObject to the Renderers property of the Screen Wrap component in the Inspector for the Asteroid GameObject.
Finally, drag the Asteroid from the Hierarchy to the Prefab folder in the Project window. Click Original Prefab when prompted to create the Prefab. Now that you’re done creating your Asteroid Prefab, delete the Asteroid instance from the Hierarchy.
The last thing you need is a spawn point for all the asteroids. Click the Create button in the Hierarchy and select Create Empty. Name your spawn point Debris.
You’ll want this spawn point to be on the same plane as the player. Otherwise, the player will either fly over or under the debris. A good GameObject to use as a reference is missile_R_0, since it’s located in the center of the model.
Drag the Debris GameObject and make it a child of missile_R_0. The transform coordinates of Debris will then be relative to its parent GameObject.
To match the coordinates of the parent, set the Debris position to X:0, Y:0, Z:0). With this little trick you can be sure that Spaceship and Debris are on the same plane.
Next, move the Debris to the bottom of the Hierarchy view where it originally was.
Move the Debris GameObject 7.5 points to the right. In case you didn’t manage to get that all exactly the same, its new position should be (X:20.0, Y:1.72, Z:7.06).
Putting it all Together
Now that you have your ship and an asteroid configured, you need to bring all the elements together and create a simple game.
Click the Create button in the Hierarchy and select Create Empty. In Inspector, click on the name of the new GameObject and name it GameManager.
With the GameManager selected in the Hierarchy, click the Add Component button, select Scripts, then select GameManager.
You’ll see that this action added an Audio Source as well. Also, the GameManager component has several fields that you need to set that it’ll use to spawn asteroids.
Start with the Debris field. Make sure the GameManager is selected in the Hierarchy, and drag the Asteroid Prefab into the Debris field.
So what did you do here? The GameManager is responsible for spawning Asteroids. It uses the Debris field to decide which objects to spawn. You told it to use the Asteroid prefab.
Next, still on GameManager:
The GameManager component should look like the following:
Finally, in the Audio Source component, add background-music to the AudioClip field, and make sure to check the loop checkbox.
Run your game and check out how everything looks.
Congratulations – you’ve built your very first game in Unity!
In later tutorials, you’ll learn about the various subsections of Unity that really let you juice this game up. You’ll also learn how to write your own scripts to take advantage of Unity’s flexible API.
… and you did remember to save your work. Right? ;]
Where to Go From Here?
If you like, you can open the final project from the Download Materials link at the top or bottom of this tutorial.
As always, keep checking this site for more Unity tutorials. If you have any questions, feel free to reach out to me in the comments below!