Marte Engine Graphic Rogue Like Tutorial 09

Wandering monsters! 

Welcome reader to this tutorial! I'll show you how to build a roguelike with MarteEngine. For more information about MarteEngine, please see http://github.com/Gornova/MarteEngine. This tutorial is inspired from same serie from Trystan and follow the same organization, so let's start!
In this tutorial we'll add more interesting type of monsters, wandering one!

Bat 

First of all we need to define bat class:

package merlTut;

import it.marteEngine.ResourceManager;

public class Bat extends Creature {

 public Bat(float x, float y, int maxHp, int attack, int defense,
   int visionRadius) {
  super(x * tileSize * scaleFactor, y * tileSize * scaleFactor, maxHp,
    attack, defense, visionRadius);

  setGraphic(ResourceManager.getSpriteSheet("char").getSubImage(14, 12)
    .getScaledCopy(scaleFactor));

  addType(BAT);
  setHitBox(0, 0, tileSize * scaleFactor, tileSize * scaleFactor);
 }
 
}

Because we have already defined Creature class for Fungus, adding a new monster is not an hard task, just add new Creature type on Creature class:

 public final String BAT = "bat";

and add a check on move method:

    public void move(int dx, int dy) {
  float cx = x + dx * step;
  float cy = y + dy * step;
  if (cx >=0 && cx < world.width && cy > 0 && cy < world.height){
   if (collide(new String[]{Tile.WALL,FUNGUS, Tile.STAIRS_UP, Tile.STAIRS_DOWN, BAT}, cx, cy) == null) {
    x = cx;
    y = cy;
   }
  }
 }

Bat is a wandering monsters so add a wander method on CreatureAi class:

 
    public void wander(){
        int mx = (int)(Math.random() * 3) - 1;
        int my = (int)(Math.random() * 3) - 1;
        creature.move(mx, my);
    }

Like for Trystan's tutorial wander it's simple enough for our bat, so define a BatAi using wandering:

package merlTut;

import it.marteEngine.entity.Entity;

public class BatAi extends CreatureAi {

    private CreatureFactory factory;

 public BatAi(Creature creature, CreatureFactory factory) {
        super(creature);
        this.factory = factory;
    }

 @Override
    public void update(){
        wander();
        wander();
    }
 
 @Override
 public void collide(Entity other) {
  if (other instanceof Hero) {
   Hero hero = (Hero)other;
   hero.attack(creature);
  }
 } 
}

Adding bats to the game

We add to Creature factory an utility method for bats:

public Bat newBat(){
  Bat bat = new Bat(0, 0,10,0,0,0);
  bat.name = "Bat";
  bat.setCreatureAi(new BatAi(bat,this));
  return bat;
 }

and call it from GameWorld newLevel method:

private void newLevel() {
  // we destroy everything
  clear();
  // add random generated cave
  levelBuilder = new LevelBuilder(tileWidth, tileHeight).makeCaves()
    .addStairs();
  level = levelBuilder.build();
  addAll(level.getEntities(), GAME);
  // add some fungus at free random locations
  for (int i = 0; i < 8; i++) {
   addAtEmptyRandomLocation(creatureFactory.newFungus());
  }
  //add some bats
  for (int i = 0; i < 15; i++) {
   addAtEmptyRandomLocation(creatureFactory.newBat());   
  }
  // add hero at first free place
  hero = creatureFactory.newHero();
  addAtEmptyLocation(hero);

  // setting camera:
  this.setCamera(new Camera(this, hero, container.getWidth(), container
    .getHeight(), 512, 512, new Vector2f(32, 32)));
  setWidth(tileWidth * tileSize * scaleFactor);
  setHeight(tileHeight * tileSize * scaleFactor);

  messages.clear();
  clearMessagesTimer = 0;
 }

Fifhteen bats is enough for now!

Bats.. everywhere!

 Conclusion 

Adding new creatures is easy: decide image on spritesheet, define a new class, a new ai and using CreatureFactory we can add new bats in our dungeons!

You can download source code from here.