AI

Some in-built support for writing game AIs is given in the engine. The AITaskComponent (code) can be given a list of priority tasks. Every frame, it calculates the priority of each task, and runs the highest priority one. A task should be able to be started and stopped at any time, and can succeed, fail, or run forever. The power of this task-based system is that a task can be made up of smaller sub-tasks.

For example, the ghost enemy AI has the following tasks:

• WanderTask with constant priority 1.
• ChaseTask with a low priority if the player is not visible, but a high priority if the player is visible.

This allows the ghost to chase the player only while they are in line of sight. The wander task is made up of two smaller tasks:

• MoveTask to move to a random location.
• WaitTask to wait for a bit before moving again.

Note that these tasks do not need priorities, since they are run repeatedly in a sequence inside the wander task. MoveTask is also used inside of ChaseTask to let the ghost move towards the player. By splitting the AI's actions into smaller tasks, we can reuse the same code in multiple places!

Usage

Using the AI task component is as simple as attaching it to an entity and giving it the priority tasks you want it to run. It will always run the highest priority one available. For example:

public Entity createEnemy() {
  AITaskComponent aiComponent = new AITaskComponent()
    .addTask(new WanderTask())
    .addTask(new ChaseTask(player));
  
  return new Entity()
    .addComponent(aiComponent);
}