A* Search Algorithm

Author: redomar

src/com/redomar/game/entities/Dummy.java

@@ -7,6 +7,7 @@
 import com.redomar.game.gfx.Colours;
 import com.redomar.game.gfx.Screen;
 import com.redomar.game.level.LevelHandler;
+import com.redomar.game.level.Node;
 
 public class Dummy extends Mob {
 
@@ -17,6 +18,8 @@ public class Dummy extends Mob {
 	private boolean[] swimType;
 	private int[] swimColour;
 	private static double speed = 0.75;
+	private List<Node> path = null;
+	private int time = 0;
 
 	private Swim swim;
 
@@ -30,13 +33,10 @@ public Dummy(LevelHandler level, String name, int x, int y, int shirtCol,
 
 	public void tick() {
 
-		List<Player> players = level.getPlayers(this, 8);
-		if (players.size() > 0) {
-			followMovementAI((int) getX(), (int) getY(), (int) Game.getPlayer().getX(), (int) Game
-					.getPlayer().getY(), xa, ya, speed, this);
-		}else{
-			isMoving = false;
-		}
+		//List<Player> players = level.getPlayers(this, 8);
+		aStarMovementAI((int) getX(), (int) getY(), (int) Game.getPlayer().getX(), (int) Game
+					.getPlayer().getY(), xa, ya, speed, this, path, time);
+		
 
 		setSwim(new Swim(level, (int) getX(), (int) getY()));
 		swimType = getSwim().swimming(isSwimming, isMagma, isMuddy);
@@ -49,6 +49,7 @@ public void tick() {
 	}
 
 	public void render(Screen screen) {
+		time++;
 		int xTile = 8;
 		int yTile = 28;
 		int walkingSpeed = 4;

src/com/redomar/game/entities/Mob.java

@@ -1,9 +1,12 @@
 package com.redomar.game.entities;
 
+import java.util.List;
 import java.util.Random;
 
 import com.redomar.game.level.LevelHandler;
+import com.redomar.game.level.Node;
 import com.redomar.game.level.tiles.Tile;
+import com.redomar.game.lib.utils.Vector2i;
 
 public abstract class Mob extends Entity {
 
@@ -155,6 +158,25 @@ protected boolean isSolid(int xa, int ya, int x, int y) {
 
 		return false;
 	}
+	
+	protected void aStarMovementAI(int x, int y, int px, int py, double xa,
+			double ya, double speed, Mob mob, List<Node> path, int time){
+		xa = 0;
+		ya = 0;
+		Vector2i start = new Vector2i(x >> 3, y >> 3);
+		Vector2i goal = new Vector2i(px >> 3, py >> 3);
+		path = level.findPath(start, goal);
+		if(path != null) {
+			if(path.size() > 0){
+				Vector2i vector = path.get(path.size() - 1).tile;
+				if(x < vector.getX() << 3) xa++;
+				if(x > vector.getX() << 3) xa--;
+				if(y < vector.getY() << 3) ya++;
+				if(y > vector.getY() << 3) ya--;
+			}
+		}
+		moveMob(xa, ya, mob);
+	}
 
 	protected void followMovementAI(int x, int y, int px, int py, double xa,
 			double ya, double speed, Mob mob) {

src/com/redomar/game/level/LevelHandler.java

@@ -4,6 +4,8 @@
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 import java.util.logging.Level;
 
@@ -15,6 +17,7 @@
 import com.redomar.game.entities.PlayerMP;
 import com.redomar.game.gfx.Screen;
 import com.redomar.game.level.tiles.Tile;
+import com.redomar.game.lib.utils.Vector2i;
 import com.redomar.game.net.packets.Packet01Disconnect;
 
 public class LevelHandler {
@@ -26,6 +29,16 @@ public class LevelHandler {
 	private String imagePath;
 	private BufferedImage image;
 
+	private Comparator<Node> nodeSorter = new Comparator<Node>() {
+
+		public int compare(Node n0, Node n1) {
+			if(n1.fCost < n0.fCost) return +1;
+			if(n1.fCost > n0.fCost) return -1;
+			return 0;
+		}
+		
+	};
+	
 	public LevelHandler(String imagePath) {
 
 		if (imagePath != null) {
@@ -194,6 +207,60 @@ public void movePlayer(String username, int x, int y, int numSteps,
 		player.setMovingDir(movingDir);
 	}
 
+	public List<Node> findPath(Vector2i start, Vector2i goal){
+		List<Node> openList = new ArrayList<Node>();
+		List<Node> closedList = new ArrayList<Node>();
+		Node current = new Node(start, null, 0, getDistance(start, goal));
+		openList.add(current);
+		while(openList.size() > 0){
+			Collections.sort(openList, nodeSorter);
+			current = openList.get(0);
+			if(current.tile.equals(goal)){
+				List<Node> path = new ArrayList<Node>();
+				while (current.parent != null) {
+					path.add(current);
+					current = current.parent;
+				}
+				openList.clear();
+				closedList.clear();
+				return path;
+			}
+			openList.remove(current);
+			closedList.add(current);
+			for(int i = 0; i < 9; i++){
+				if(i == 4) continue;
+				int x = current.tile.getX();
+				int y = current.tile.getY();
+				int xi = (i % 3) - 1;
+				int yi = (i / 3) - 1;
+				Tile at = getTile(x + xi,y + yi);
+				if(at == null) continue;
+				if(at.isSolid()) continue;
+				Vector2i a = new Vector2i(x + xi, y + yi);
+				double gCost = current.gCost + getDistance(current.tile, a);
+				double hCost = getDistance(a, goal);
+				Node node = new Node(a, current, gCost, hCost);
+				if(isVectorInList(closedList, a) && gCost >= node.gCost) continue;
+				if(!isVectorInList(openList, a) || gCost < node.gCost) openList.add(node);
+			}
+		}
+		closedList.clear();
+		return null;
+	}
+	
+	private boolean isVectorInList(List<Node> list, Vector2i vector){
+		for(Node n : list){
+			if(n.tile.equals(vector)) return true;
+		}
+		return false;
+	}
+	
+	private double getDistance(Vector2i tile, Vector2i goal){
+		double dx = tile.getX() - goal.getX();
+		double dy = tile.getY() - goal.getY();
+		return Math.sqrt(dx * dx + dy * dy);
+	}
+	
 	public List<Entity> getEntities(Entity e, int radius){
 		List<Entity> result = new ArrayList<Entity>();
 		int ex = (int) e.getX();

src/com/redomar/game/level/Node.java

@@ -0,0 +1,19 @@
+package com.redomar.game.level;
+
+import com.redomar.game.lib.utils.Vector2i;
+
+public class Node {
+	
+	public Vector2i tile;
+	public Node parent;
+	public double fCost, gCost, hCost;
+	
+	public Node(Vector2i tile, Node parent, double gCost, double hCost){
+		this.tile = tile;
+		this.parent = parent;
+		this.gCost = gCost;
+		this.hCost = hCost;
+		this.fCost = (this.gCost + this.hCost);
+	}
+
+}

src/com/redomar/game/lib/utils/Vector2i.java

@@ -0,0 +1,61 @@
+package com.redomar.game.lib.utils;
+
+public class Vector2i {
+	
+	private int x, y;
+	
+	public Vector2i(){
+		set(0, 0);
+	}
+	
+	public Vector2i(int x, int y){
+		set(x, y);
+	}
+	
+	public Vector2i(Vector2i vector){
+		set(vector.x, vector.y);
+	}
+	
+	public Vector2i add(Vector2i vector){
+		this.x += vector.x;
+		this.y += vector.y;
+		return this;
+	}
+	
+	public Vector2i subtract(Vector2i vector){
+		this.x -= vector.x;
+		this.y -= vector.y;
+		return this;
+	}
+	
+	public boolean equals(Object object){
+		if (!(object instanceof Vector2i)) return false;
+		Vector2i vector = (Vector2i) object;
+		if(vector.getX() == this.getX() && vector.getY() == this.getY()) return true;
+		return false;
+	}
+	
+	public void set(int x, int y){
+		this.x = x;
+		this.y = y;
+	}
+
+	public int getX() {
+		return x;
+	}
+
+	public Vector2i setX(int x) {
+		this.x = x;
+		return this;
+	}
+
+	public int getY() {
+		return y;
+	}
+
+	public Vector2i setY(int y) {
+		this.y = y;
+		return this;
+	}
+
+}