FREE Basic Tower Defence Spawn System

Hey Guys!

I've just finished making this really simple tower defence styled spawn system, and thought I would upload it here for you to use in your own games.
The script is in C# and I have heavily commented it so it should be easy for a beginner to understand what's going on.
The spawn system allows you to spawn an enemy at a random xz value on a circumference, between a minimum and maximum distance from the target.
It will place enemies onto the surface of terrain so it will not matter if you have hills or mountains around your target.
Enemies will spawn in waves, increasing by 5 enemies each wave (but this value can easily be adjusted).

Instructions for use:

1) Attach "SpawnSystem" onto your tower/target/whatever

2) Plug your enemy prefab into the inspector. (Note that your enemy needs to have a CharacterController component added)

3) Press play!

Extra:

If you are using a terrain, ensure that you check "use terrain" as true. Otherwise this value must be false.

Ensure that the ground/floor in your game is positioned at 0 on the y axis. (if this is not possible, adjust the "spawn height offset" in the inspector to the required value)

By increasing the "spawn height offset" to a number like 100, enemies will appear to fall from the sky.

Here is the script. Feel free to use any part of the code in any of your projects :wink:

Code (csharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SpawnSystem : MonoBehaviour {
5.     //Your enemy character prefab (Must have a character controller component)
6.     public GameObject enemyPrefab;
7.     //How high above the ground you want your enemy spawned (0 = ground level)
8.     public float spawnHeightOffset = 0.0f;
9.     //The minimum distance from the target your enemies will spawn
10.     public float spawnRadiusMin = 20.0f;
11.     //The maximum distance from the target your enemies will spawn
12.     public float spawnRadiusMax = 30.0f;
13.     //The amount of time between each spawn
14.     public float spawnDelay = 0.5f;
15.     //Are you using a terrain? Script uses this to calculate how high above the enemy needs to be placed on spawn
16.     public bool useTerrain = true;
17.    
18.     //How tall is your enemy character
19.     private float enemyHeight;
20.     //What is the current wave
21.     private int curWave = 1;
22.     //Is the spawn system currently spawning enemies
23.     private bool isSpawning = false;
24.     //The initial maximum number of enemies per wave
25.     private int maxEnemies = 5;
26.     //The current enemies in the scene
27.     private GameObject[] curEnemies;
28.     //The selected spawn point (Random angle and distance from target)
29.     private Vector3 spawnPoint;
30.    
31.     void Start () {
32.         //Find what the height of the enemy's CharacterContoller component is
33.         enemyHeight = enemyPrefab.GetComponent<CharacterController>().height;
34.         //Begin the first wave
35.         StartCoroutine(SpawnEnemy());
36.     }
37.    
38.     void Update () {
39.         //Check if the script is NOT spawning enemies
40.         if (!isSpawning) {
41.             //Check how many enemies are still in the scene
42.             curEnemies = GameObject.FindGameObjectsWithTag("Enemy");
43.             //When there are no more enemies left, increase the current wave
44.             if (curEnemies.Length <= 0) {
45.                 IncreaseWave();
46.             }
47.         }
48.     }
49.    
50.     IEnumerator SpawnEnemy () {
51.         //Tell script that we are currently spawning enemies
52.         isSpawning = true;
53.         //Loop until script has spawned the maximum number of enemies for this round
54.         for (int i = 0; i < maxEnemies; i++) {
55.             //Delay between spawning
56.             yield return new WaitForSeconds(spawnDelay);
57.             //Find a random spawn point
58.             FindSpawnPoint(Random.Range(spawnRadiusMin, spawnRadiusMax), Random.Range(0, 359));
59.             //Spawn an enemy at the random spawn point
60.             Instantiate(enemyPrefab, spawnPoint, Quaternion.identity);
61.         }
62.         //Tell script that we are finished spawning enemies for this round
63.         isSpawning = false;
64.     }
65.    
66.     Vector3 FindSpawnPoint(float spawnRadius, int angleInDegrees) {
67.         //find a random point on the circumference of a circle, with random radius from target between specified min / max distance
68.         float pointX = (spawnRadius * Mathf.Cos(angleInDegrees * Mathf.PI / 180.0f)) + transform.position.x;
69.         float pointZ = (spawnRadius * Mathf.Sin(angleInDegrees * Mathf.PI / 180.0f)) + transform.position.z;
70.         //Set the spawn point into a Vector3
71.         spawnPoint = new Vector3(pointX, 0.0f, pointZ);
72.         //Are we using a terrain?
73.         if (useTerrain) {
74.             //Adjust the spawn points y value to account for terrain relief
75.             spawnPoint.y = Terrain.activeTerrain.SampleHeight(spawnPoint);
76.         }
77.         //Add half of the enemies height to the y value (So that his feet are on the ground, not waist deep)
78.         spawnPoint.y += (enemyHeight / 2) + spawnHeightOffset;
79.         //Return the final spawn point
80.         return spawnPoint;
81.     }
82.    
83.     void IncreaseWave () {
84.         //Increase the current wave by 1
85.         curWave++;
86.         //Increase the maximum number of enemies for this wave
87.         maxEnemies = curWave * 5;
88.         //Start the next wave
89.         StartCoroutine(SpawnEnemy());
90.     }
91.    
92.     void OnGUI () {
93.         //Display the wave number in the top left corner of screen
94.         GUI.Label(new Rect(5, 5, 100, 30), "Wave " + curWave.ToString());  
95.     }
96. }

Tell me what you think.

 

check your link, saves as a 1x1 .gif

 

Sorry, had some problems trying to set up a download link. Just copy / paste code to use.

 

very nice script,
thank you for sharing