15 - Turret Spawner

Challenge: Create an OnCursorClick event

To be able to detect when the player has clicked on a tile, you will add a new event to the TileController that can be used to forward click events.

verify-on-cursor-click-inspector.png

  • Add a NotifyCursorClicked() method that invokes OnCursorClick
  • In your Tile Prefab update the model's OnClick event to invoke the NotifyCursorClicked method.

on-click-notify-cursor-clicked.png

TurretSpawner

Now that you have an event that sends an event when a tile is clicked, you add in a Turret Spawner that will listen for clicks. If the tile is not occupied, it will spawn a turret at that location.

  • Create a new MonoBehaviour called TurretSpawner
  • Add a GameObject TurretPrefab property to your TurretSpawner
  • Add the [field: SerializeField] attribute to the TurretPrefab property

15 - Spawning a Turret.png

  • Create a new GameObject in the Turret Spawn Test Scene, this will be your TurretSpawner
  • Add the TurretSpawner component
  • In the Inspector set the TurretPrefab to use the prefab you created for your Turret

SpawnTurret(TileController)

  • Add a SpawnTurret(TileController) method to your TurretSpawner
  • In SpawnTurret, check to see if the specified TileController IsOccupied .
  • If it is, do nothing. (return)
  • If it is not occupied, Instantiate a TurretPrefab and set the position to match the position of the TileController

SpawnTurretMethod.png

Testing SpawnTurret

Before writing a handler to register your TurretSpanwer on all tiles, it is helpful to test if the SpawnTurret method is working against a single tile.

  • In the Hierarchy select a Tile
  • In the Inspector add listener to the OnCursorClick event
  • Add your TurretSpanwer as the listening object
  • Select the TurretSpawner.SpawnTurret method as the method to invoke
  • Take note of the tile that you updated.
  • Enter Play Mode and click on that tile, if all went well, a turret was spawned into the scene

Bug: Cursor Blocked

You likely noticed that after you placed your turret, the cursor stops registering on tiles that are near your turret. This is because the collider the turret is using to detect enemies is blocking the tile. To prevent this, you can create Collision Layers for your objects and specify which layers mouse events detect.

Adding a Tile Collision Layer

  • From the top menu select Edit > Project Settings

  • On the left side, select the Tags and Layers tab
    Assets/m15-Spawning a Turret/tags-and-layers.png

  • If necessary, open the Layers drop down. (Ensure you are not in Sorting Layers / Rendering Layers)

  • Add a Tiles layer
    add-tile-layer.png

Apply the Tile Layer to your Tile Prefabs

  • In the Project explorer tab, navigate to your Prefabs > Tiles folder
  • Select all of your Tile prefabs
  • In the Inspector, change the Layer to Tile
  • When prompted, select change children
  • This will apply the Tile layer to all of your tile objects and their models

Challenge: Update Camera Culling to Include Tiles

If you switch to the Game tab or enter Play Mode you will no longer see your tiles. This is because the Camera does not render them.

  • Update the camera's Culling Mask to see the Tile layer

Camera Event Layer

By default, the Camera will detect all collision layers. This means that your mouse is being blocked by your turrets area of engagement collider. To fix this, you must change which layers the camera allows the mouse to interact with. This is called the Camera's Event Layer.

Unfortunately, there is no way to set this in the Inspector. But, it is possible to modify the Camera.eventMask field using a script.

  • Read the Friendly Manual: Unity - Scripting API: Camera.eventMask
  • Read the Friendly Manual: Unity - Scripting API: LayerMask
  • Create a new MonoBehaviour called CameraEventMaskController
  • Add a LayerMask EventMask property
    eventmask.png
  • In the Hierarchy select your Main Camera
  • In the Inspector, add a CameraEventMaskController
  • Set the EventMask to Tile
  • Add an Awake() method to your CameraEventMaskController
  • In Awake()
  • Use GetComponent<Camera>() to find the Camera component
  • Set the camera's eventMask to the EventMask property
    15 - Spawning a Turret 1.png
  • Enter Play mode and test that you can still see the selected tile after placing a turret

Challenge: Listen to all tiles

Now that you have verified that you can spawn a single turret, you are ready to listen to all of the tiles in a grid.

  • Remove the listener you added to the tile in your scene
  • Review how you listen to all tiles in TileCursor
    Update TurretSpawner such that
  • OnEnable, listen to all of the tiles in your test scene's grid
  • OnDisable, stop listening to all of the tiles in your test scene's grid

When you have finished, you should be able to click on any tile in the scene to spawn a turret:

Bug: Spawning Multiple Turrets on the Same Tile

Currently, if you click the same tile multiple times, it will spawn multiple turrets. This is because you never set tilecontroller.IsOccupied to true after spawning a turret in SpawnTurret Can you fix this bug?

  • Update SpawnTurret to set tileController.IsOccupied to true
  • Hint: You will also need to modify TileController

What's Next?

Now that you are able to spawn turrets on a tile, it is time to add a TileCursor and a TurretSpawner to your map. In the next lesson, you will learn how to add a button that enables the player to build a turret in your level.

16 - Placing Turrets

Table Of Contents
15 - Turret Spawner
Challenge: Create an OnCursorClick event
TurretSpawner
SpawnTurret(TileController)
Testing SpawnTurret
Bug: Cursor Blocked
Adding a Tile Collision Layer
Apply the Tile Layer to your Tile Prefabs
Challenge: Update Camera Culling to Include Tiles
Camera Event Layer
Challenge: Listen to all tiles
Bug: Spawning Multiple Turrets on the Same Tile
What's Next?