Lesson 2.4 - Collision Decisions

Our game is coming along nicely, but there are are some critical things we must add before it’s finished. First off, instead of pressing S to spawn the animals, we will spawn them on a timer so that they appear every few seconds. Next we will add colliders to all of our prefabs and make it so launching a projectile into an animal will destroy it. Finally, we will display a “Game Over” message if any animals make it past the player.

​Make a new method to spawn animals

  1. In SpawnManager.cs, create a new void SpawnRandomAnimal() {} function beneath Update()
  2. Cut and paste the code from the if-then statement to the new function
  3. Call SpawnRandomAnimal(); if S is pressed

​Spawn the animals at timed intervals

  1. In Start(), use InvokeRepeating to spawn the animals based on an interval, then test.
  2. Remove the if-then statement that tests for S being pressed
  3. Declare new private startDelay and spawnInterval variables then playtest and tweak variable values

​Add collider and trigger components

  1. Double-click on one of the animal prefabs, then Add Component > Box Collider
  2. Click Edit Collider, then drag the collider handles to encompass the object
  3. Check the “Is Trigger” checkbox
  4. Repeat this process for each of the animals and the projectile
  5. Add a RigidBody component to the projectile and uncheck “use gravity” ​

​Destroy objects on collision

  1. Create a new DetectCollisions.cs script, add it to each animal prefab, then open it
  2. Before the final } add OnTriggerEnter function using autocomplete
  3. In OnTriggerEnter, put Destroy(gameObject);, then test
  4. In OnTriggerEnter, put Destroy(other.gameObject);

​Trigger a “Game Over” message

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  1. In DestroyOutOfBounds.cs, in the else-if condition that checks if the animals reach the bottom of the screen, add a Game Over messsage: Debug.Log(“Game Over!”)
  2. Clean up your code with comments
  3. If using Visual Studio, Click Edit > Advanced > Format document to fix any indentation issues (On a Mac, click Edit > Format > Format Document)