ReMonkey Tutorial #2: Ninja & Pirates!

Pesegato · March 30, 2015, 8:11am

Link to previous tutorial:

After checking the first tutorial, you may have noticed a type problem: the Leaf Tasks (the building blocks of the Behavior Trees) works only with RedMonkey; which is not what you want because it severely limits its usefulness.

What you want, instead, is the freedom to create new Leaf Tasks which are more suitable to your game and its component. In this tutorial we’ll see not one but two different ways to leverage Behavior Trees with custom game logic (or more properly, create new blackboard classes compatible with RedMonkey). But enough chitty-chatty, let’s have a look at RedMonkeyNinja and RedMonkeyPirate.

The Pirate

Ahrr ahrr matey! I’ve digged my treasure o’ Banana and I’m ready to sail the seven seas! I just need the right Behavior Tree!

github.com

QuietOne/MonkeyBrainsDemoGames/blob/51f073f88bb2e4abdb3b23c8fbd32b851333d8f9/SteeringBehaviors/src/redmonkeyDemos/RedMonkeyPirate.java#L10-L28


      
          public class RedMonkeyPirate extends RedMonkey {
          
              int treasure;
              boolean eyePatch;
          
              public void collectBanana() {
                  treasure++;
              }
          
              public RedMonkeyPirate(float x, float y, float z, TerrainQuad terrain, Spatial model, GameLogicHook gameLogic, float yTranslation, String... newTags) {
                  super(x, y, z, terrain, model, gameLogic, yTranslation, newTags);
              }
          
              @Override
              public void setBehaviorTree(AssetManager assetManager, String tree) {
                  BehaviorTreeParser<RedMonkeyPirate> parser = new BehaviorTreeParser<>(BehaviorTreeParser.DEBUG_NONE);
                  behaviorTree = parser.parse((String) (assetManager.loadAsset(tree)), this);
              }
          }

The class RedMonkeyPirate extends RedMonkey; so that it is possible to create LeafTask (and therefore Behavior Tree) more game-specific. The LeafTask for RedMonkeyPirate must be declared like this:

github.com

QuietOne/MonkeyBrainsDemoGames/blob/51f073f88bb2e4abdb3b23c8fbd32b851333d8f9/SteeringBehaviors/src/redmonkeyDemos/CollectBananaTask.java#L10-L24


      
          public class CollectBananaTask<T extends RedMonkey> extends LeafTask<T> {
          
              @Override
              public void run(T t) {
                  RedMonkeyPirate pirate = (RedMonkeyPirate) t;
                  pirate.collectBanana();
                  success();
              }
          
              @Override
              protected Task<T> copyTo(Task<T> task) {
                  CollectBananaTask cb = (CollectBananaTask) task;
                  return task;
              }
          }

Ahrr ahrr! Let’s put the hook on! But if you prefer a katana to a hook, let’s have a look at…

The Ninja

Ninjas are swift, deadly, and go straight to the point. RedMonkeyNinja is no exception:

github.com

QuietOne/MonkeyBrainsDemoGames/blob/51f073f88bb2e4abdb3b23c8fbd32b851333d8f9/SteeringBehaviors/src/redmonkeyDemos/RedMonkeyNinja.java#L8-L21


      
          class RedMonkeyNinja {
          
              int numkills;
          
              public RedMonkeyNinja(float x, float y, float z, TerrainQuad terrain, Spatial model, GameLogicHook gameLogic, float yTranslation, String... newTags) {
                  RedMonkey redMonkey = new RedMonkey(x, y, z, terrain, model, gameLogic, yTranslation, newTags);
                  redMonkey.container = this;
          
              }
          
              public void kill() {
                  numkills++;
              }
          }

RedMonkeyNinja sets itself as the container for RedMonkey, meaning that RedMonkey become a property of RedMoneyNinja in a pseudo-entity style. No inheritance involved. Of course, we have a runtime casting in the LeafTask:

github.com

QuietOne/MonkeyBrainsDemoGames/blob/51f073f88bb2e4abdb3b23c8fbd32b851333d8f9/SteeringBehaviors/src/redmonkeyDemos/KillTask.java#L10-L24


      
          public class KillTask extends LeafTask<RedMonkey> {
          
              @Override
              public void run(RedMonkey monkey) {
                  RedMonkeyNinja ninja = (RedMonkeyNinja) monkey.container;
                  ninja.kill();
                  success();
              }
          
              @Override
              protected Task<RedMonkey> copyTo(Task<RedMonkey> task) {
                  KillTask kill = (KillTask) task;
                  return task;
              }
          }

Thanks for reading!