16 - Placing Turrets
Challenge: Create a TurretSpawner Prefab
To be able to use your TurretSpanwer in any scene, you can turn it into a prefab.
- Turn your
TurretSpawnerinto a prefab
Practice: Update Your Level's Camera
- Open your level scene
You'll notice that in your level scene, your camera no longer renders your Tiles. This is because you moved yourTileprefabs to theTilelayer. - Update your main camera's culling mask to show the
Tilelayer
Add a TileCursor and TurretSpawner
- Add a
TileCursorand aTurretSpawnerto your scene - In the Inspector, set your
TileCursorandTurretSpawnerto listen to the tiles in your level's grid
- Enter Play Mode and test that you can now place turrets
Practice: Fix Layer Collisions
You may have noticed that you are unable to place turrets within another turrets Area of Engagement. Recall that you fixed this for your Test Scene in 15 - Turret Spawner > Camera Event Layer.
- Update your camera to only interact with the
Tilelayer
Create a GameCamera Prefab
As you continue to add new scenes to your game, you may need to adjust the camera again. Ideally, the camera will work the same in every scene. To help create this consistency, you can create a GameCamera prefab that can be reused in your test scenes. Additionally, it can be useful to have the camera nested in a parent object just in case you need to add sibling game objects.
- In the Hierarchy, create a parent object for your
Main Cameraand name it GameCamera - Turn the GameCamera object into a Prefab
Practice: Remove existing Turrets
Now that you have a way to spawn turrets into your scene during Play Mode, you can remove the starting turrets from the scene.
- Remove any turrets that you placed directly in your scene
Creating a Place Turret Button
Next, you will add a button to your scene that enables the TileCursor and TurretSpawner GameObjects when clicked.
Enabling and Disabling TileCursor and TurretSpawner
Verify that disabilng TileCursor and TurretSpawner disables the ability to place turrets.
- Select both
TileCursorandTurretSpawnerin the Hierarchy - In the Inspector, disable both game objects
- Enter Play Mode and verify that you can no longer place turrets
- While in Play Mode enable both
TileCursorandTurretSpawner - Verify that you can place turrets while they're enabled
Add a Button to your Scene
- In the Hierarchy, click the
+icon - Select
UI>Button - TextMeshPro
The first time you add a TextMeshPro object to a Unity Project, you will be prompted to import the Text Mesh Pro library.
- Import Text Mesh Pro Essentials
- You do not need to Import the Examples & Extras
After the library has been imported, you should see 3 new Game Objects in your Hierarchy
What is a Canvas/EventSystem
You may be wondering what are the Canvas and EventSystem objects that were added to your scene. The Canvas in Unity is a component that acts as the root for all UI elements, determining how they are rendered and positioned in the game world or screen space. The EventSystem is responsible for processing and managing user input, such as mouse clicks, touches, and controller interactions, ensuring that UI elements respond correctly. Together, the Canvas and EventSystem enable interactive user interfaces by handling rendering and input events within Unity’s UI system.
Positioning the Button
If you are in the Scene tab, you probably do not see the Button you added. This is because the button is added to the Canvas which, by default, exists as a screen overlay.
- Open the Game view tab
- Verify that there is a button in the center of the screen
In the Scene view, you can switch to 2D mode to more easily view the button on the canvas. - Open the Scene view tab
- Select the 2D mode in the top right of the Scene view
- Double click on the Canvas in the Hierarchy to focus the camera on the canvas
Moving the Button
- Select the Move tool
- Move the Button to the bottom left corner of the canvas
Different Screen Resolutions
Unfortunately, setting the position of the button in this way will only work if your player is using the exact same resolution as you. Unity provides tools for testing different resolutions so you can determine how your game will work in different screen modes.
- Open the Game view tab
- Toggle between different resolutions
- Observe the button moving to different screen positions
UI Pivots
This is happening because your button was positioned relative to the center of the screen. Thus, if the user is using a smaller resolution, the button will appear closer to the center of the screen. To help with this, Unity provides a way to specify a Pivot point.
- Select the your Button from the Hierarchy
- In the Inspector, find the Rect Transform component
- Click the Pivot icon to open the "quick" pivot and anchor settings
- Click the Bottom Left Corner pivot icon
This sets the objects position to be relative to the bottom left corner of the users screen regardless of their resolution. - If necessary, adjust the buttons position so it is near the bottom left corner
- Enter Play Mode
- Change Resolutions
- Observe that the button doesn't change position
- The size of the button may appear to change -- however, this is because the zoom scale is changing.
Button.OnClick Listener
By default, Unity's UI button object comes with an OnClick Listener that can be used in the Inspector to invoke a method on an object.
-
Select your button in the Hierarchy
-
In the Inspector find the
Buttoncomponent -
Within the
Buttoncomponent, locate theOn Clickevent -
Add a Listener by clicking the
+icon
-
Add the
TileCursorto the listener -
Invoke the
GameObject.SetActivemethod and set it to true (enable checkbox)
-
Enter Play Mode
-
Verify that the cursor does not display if you move on a tile
-
Click the Button
-
Verify that the cursor does display if you move on a tile
Practice: Enable TurretSpawner
- Update the button such that it will enable both the TileCursor and TurretSpawner when the button is clicked
When you're finished, your game should operate similar to the video below
Changing the Button Text
- Expand the Button in the Hierarchy
- Select the Text (TMP) child
- In the Inspector find the Text component
- Update the Text component to display "Build"
What's Next?
Now that you have a basic understanding about adding a button to your scene that can invoke methods on your other GameObjects, it is time to add in resources that will determine if the player is able to place a turret on the map.