Enemy Spawning

Spawning in objects is a crucial part of a great deal of games.

In Godot, we first need a scene to instantiate. Instantiating something means making a copy of it, AKA making an instance of it.

Next, we need to set any variables it might need.

Finally, add it to the scene tree so it’s actually in the game world.
This will be when the @onready variables and the _ready function finally run, since they run when a node is added to the scene tree. After those run, it’ll begin _physics_process and _process.

Enemies

Section titled Enemies

The way we spawn enemies is ultimately up to you. You could spawn them at random points around the map but not on the player, you could make a bunch of spawners that continuously spew enemies, perhaps make it a goal for the player to close all the spawners.

For now, we’re just going to spawn enemies around the player, but just outside their camera.

1. Make a Path2D node as a child of Camera2D in your player scene, then a PathFollow2D node and a Timer node as a child of Path2D.

   The Godot docs have a perfect example of doing this, it’s recommended you go through the Spawning Mobs section there to make the points on your Path2D, but we’ll go through it quickly too.

2. Select Path2D and use the green tool in the toolbar’s Path2D tools, Add Point. This tool is used to add points to the path. Also, toggle on the Use Smart Snap and Use Grid Snap options in the toolbar.

   In clockwise order, use the Add Point tool and select just outside all four corners of the camera’s pink boundary to create a path. After doing the final corner, use the final Path2D tool that comes before Options, Close Curve, to connect the path back to the beginning. You’ll want to have the points be outside of the camera, otherwise the enemies will spawn half-way on screen.

Resizing Screen

The Godot docs don’t mention this at the time of making this Path2D way, but this doesn’t scale with the screen. If you even maximize the window that Godot makes for the game, it won’t scale.

To fix this go to Project > Project Settings… > General (tab) > Display (category) > Window > Stretch (section). Change Mode to canvas_items and Aspect to keep.

This will make it so you see the exact same window and aspect ratio as everyone else. It also means that people with different aspect ratio monitors will get ugly and awful black bars to fit it into their monitor.

If you’re really confident in your programming skills, try using the size_changed signal on get_tree().root to move the points of the Path2D when the window is resized.

Script

Section titled Script

1. Add a script to your Path2D.

2. Turn Autostart on for the Timer and set its wait time to 5 seconds., then connect its timeout() signal to the mob spawner (your Path2D).

3. Get both the spawn location (PathFollow2D) and the spawn timer as variables by dragging the nodes into the script and holding ctrl/cmd before releasing click. Do the same thing with the enemy scene in your FileSystem dock.

4. At the top of your global variables in the script, add the line:

   @export_range(0.0, 1.0, 0.01) var respawn_delta: float = 0.99

   All this does is make a custom property appear on the node that can be changed in the editor without having to go into the script. This lets us quickly and easily change how quickly the spawn timer’s wait time decreases. It’s good to keep this close to 1 since it’s exponential.

5. In the function connected to the timer’s timeout() signal, write the following:

   var new_enemy: Enemy = ENEMY.instantiate()
   spawn_location.progress_ratio = randf()
   new_enemy.global_position  = spawn_location.global_position
   get_tree().root.add_child(new_enemy)
   
   spawn_timer.wait_time *= respawn_delta

   This script assumes you renamed your NodeFollow2D to SpawnLocation and your Timer to SpawnTimer before generating the variables for them by dragging them in. You can also just rename the variables to spawn_location and spawn_timer.

6. This script has an issue. I doubt you’ll be able to find it without playing the game for a few runs. But otherwise, this should work! Try playing your magical game a few times.

   Have you noticed the problem yet?

   Enemies don’t disappear when the player dies!

   Go back through and try to figure out what’s causing this, there will be no explanation, just a solution. Hint: you may want to think about how the singleton doesn’t reset, either.

   Add this code:

   var main_node: Node2D
   
   func _ready():
       main_node = get_node("/root/Main")

   Replace Main with the name of your main scene’s root node.

   Replace get_tree().root.add_child(new_enemy) with main_node.add_child(new_enemy) in the connected timeout() function.

Checklist

Section titled Checklist

• I’ve created the Path2D
• Enemies spawn along the Path
• Enemies dissapear when the player dies