Wednesday, December 28, 2016

Tower Defense Starter Kit Tutorial: How to create custom Enemy Units

[The following information is based on the v1.5 edition of Tower Defense Starter Kit & hence may not remain entirely relevant in later versions. For more information about the toolkit, check out the official support thread in the Unreal Engine forums: https://forums.unrealengine.com/showthread.php?102675-Tower-Defense-Starter-Kit-Support-Thread]


The Tower Defense Starter Kit comes equipped with four types of Enemy AI units that all derive from the parent blueprint 'BP_EnemyAI_Parent'. As the name suggests, this tutorial goes over the process of adding your own new customized AI units into the mix.

1. First add a new entry to the enum 'ECreepType. I'm going to call it Exploder as I want this new AI unit to explode when destroyed, thus dealing heavy damage to all Tower Guardians/Towers caught in the explosion.

2. Now create a new child blueprint derived from the 'BP_EnemyAI_Parent' class. By inheriting from this class, our new AI unit will have all the basic capabilities that will be required of it including damage & threat response mechanisms, movement logic, etc. At this point, all you have to do is to set the skeletal mesh & animation blueprint from it's components tab based on your requirements.

3. Set values for the default 'User Defined' attributes of this unit & add new variables named 'Explosion Damage' & 'ExplosionDamageRadius' as shown in the screenshot below:


4. Now override & extend the 'End Play' event of the parent class by adding the explosion damage application logic as shown in the previous screenshot.

[Note: Steps 5 & 6 are only required if you intend to use the Group Based Wave Generation System from the Wave Manager.]

5. Head over to the 'BP_EnemySpawnPoint' blueprint & add a custom event similar to the other SpawnCreepBatch events present in it's Event Graph. Check out the next screenshot to see how it's done. Basically this takes care of the creep spawning mechanism, once the wave generator has decided to spawn this particular type of creep.


6. Now the Wave Manager needs to know that it can call this Event to spawn a batch of Exploder bots. So make the changes marked in red in the next screenshot, within your wave manager blueprint:


7. All that's left now is to add our new Exploder bot into the Wave Data Array as shown in the example below:



With that, we have covered the steps involved in creating a very basic Enemy AI template. All classes derived from the EnemyAI_Parent class will be capable of engaging in melee combat with the Tower Guardians. If you want your custom AI bot to engage in ranged combat with the Towers as well, just follow the logic implemented within the BP_EnemyAI_Ranged blueprint.