1. MINECRAFT MOD PROGRAMMING Part III of Minecraft: Pi Edition October 31, 2015

2. Outlines Programming Python on the Pi Installing the Minecraft Pi Edition A “Hello, Minecraft!” demo 2D list (or array), how to use it? Using Minecraft modules Coding and testing a 2D board game Putting the board game into Minecraft

3. Programming Python on the Pi What are available on the Pi? Raspbian is a Debian-based free operating system optimized for the Raspberry Pi hardware (while Debian GNU/Linux is one of the most popular Linux distributions for personal computers and network servers.)Linux distributionspersonal computers network servers Midori is a lightweight WebKit browser with support for HTML5 and JavaScript Scratch programming environment Python is installed on the Raspberry Pi Python 2 & 3 Shell & IDLE

4. Setting up Minecraft on Raspberry Pi Open a web browser on Raspberry Pi Visit http://pi.minecraft.net Go to the Download page Download the latest version of the game Save the file in the /home/pi directory Open a fresh terminal and enter the following command: tar –zxvf minecraft-pi-.tar.gz Change directory with cd mcpi./minecraft-pi a new window should pop up with Minecraft: Pi Edition running inside 4

5. Client-Server Setting: how it works? Start Minecraft server (app) Clients are connected to the server (app) through socket (a fundamental networking mechanism) Client app (in Python) Minecraft Server app Socket connection command

6. Let’s start the game To start Minecraft server (app), type the following in a console: For a client to get connected to the server (app) and chat with other gamers, simply type the following in a fresh console: cd /home/pi/mcpi./minecraft-pi cd /home/pi/mcpi/api/python/mcpi python >>>import minecraft >>>mc = minecraft.Minecraft.create() >>>mc.postToChat("Hello, world!") command

7. Minecraft Programming Interface Codenamed mcpi, this API (app. prog. interface) define the ways any mod program should interact with the server Minecraft Pi Edition server implementation provides a minecraft module (relate topics in Parts I & II) An object ( mc ) in the Minecraft type can be used to mc.getBlock(x,y,z) : query the type of a block at position (x,y,z) mc.postToChat(msg) : post a message to the game chat mc.camera.setPos(x,y,z) : move the camera to a particular position mc.events.pollBlockHits() : get all blocks got hit since last poll x y z

8. The block module & the Block class The block module defines a list of all available blocks You may use a number or a name to refer to the type of blocks that you want to use Simply 3, or Use block.DIRT Details (the first few shown to the right) are at http://minecraft.gamepedia.com/ Data_values_%28Pocket_Edition%29 To add a block to a certain position (x,y,z) where 14 represents the color red mc.setBlock(x,y,z,block.WOOL,14)

9. Our first Minecraft mod project … Here is our plan: We are going to Create a board game mod … With Reversi game rules, and try to … Bring it into Minecraft Let’s first do some (OO) design (relate topics in Part II) Board Reversi ReversiMCInvalideMove Exception our_mod Block Minecraft Vec3 minecraft time

10. Detailed design for the Board class We will first see what the Board class needs to do, as well as the InvalidMoveException class Board NO_PLAYER = 0 _cols _rows _board __init__(cols,rows) get(x,y) set(x,y,player) display() InvalidMove Exception Exception class InvalidMoveException(Exception): pass

11. Now it’s time for coding! class Board: NO_PLAYER = 0 def __init__(self, cols, rows): self._board = [] self._cols = cols self._rows = rows for i in range(rows): self._board.append(cols*[Board.NO_PLAYER]) def set(self, x, y, player): if 0 <= x < self._cols and 0 <= y < self._rows: self._board[int(y)][int(x)] = player else: raise InvalidMoveException("Outside play area") def get(self, x, y): if 0 <= x < self._cols and 0 <= y < self._rows: return self._board[int(y)][int(x)] else: return Board.NO_PLAYER def display(self): print("\n".join( [" ".join([str(piece) for piece in row]) for row in self._board]))

12. Detailed design for the Reversi class We will then see what the Reversi class needs to do Define all 8 directions Use a Board object to keep track of game status Keep track players 1 – this player 2 – opponent 0 – no player: defined in Board class Get move from the console Validate a move (by checking if there is any pieces to flip) Make the move and flip pieces Output a message Start the game Reversi DIRECTIONS = […] _board _player _opponent _score __init__(x,y,player) getMove() validMove(x,y,player) piecesToFlip(x,y, player,direction) makeMove(x,y,player) set(x,y,player) output(message) display() play()

13. Getting the next move … From the console, a player should type the (0-based) column and row indices For instance, if White is the next player, a possible move is 6 6 def getMove(self): self.output("Player {0}'s move:".format(self.nextPlayer())) data = raw_input() coords = [int(coords) for coords in data.split()] coords.append(self.nextPlayer()) return coords Get input from the console Split the two #’s by the space Wrap the #’s as a list (or array) Return the list as [6, 6, 1] Append the list with player Id Wrap the #’s as a list (or array)

14. Checking pieces to flip … Try out 1 of the 8 directions in DIRECTIONS def piecesToFlip(self,x,y,player,direction): currx = x+direction[0] curry = y+direction[1] curr = self._board.get(currx,curry) print("player = " + str(curr)) pieces = [] while curr != player and curr!= Board.NO_PLAYER: pieces.append((currx,curry)) currx = currx + direction[0] curry = curry + direction[1] curr = self._board.get(currx,curry) print("curr => " + str(curr)) if curr == player: return pieces else: return [] Keep trying until the end of the streak Add a new pair of (x,y) when found Return the list of pieces to be flipped Return an empty list

15. Making a valid move… Add and flip pieces, and display results def makeMove(self,x,y,player): # Check move validity if not self.validMove(x,y,player): raise InvalidMoveException("Invalid move (" + str(x) + "," + str(y) + ")") # Place the piece self.set(x,y,player) self._score[player - 1] += 1 # Flip any appropriate pieces for direction in Reversi.DIRECTIONS: flip = self.piecesToFlip(x,y,player,direction) for x2,y2, in flip: self.set(x2,y2,player) self._score[player-1] += 1 self._score[self._opponent-1] -= 1 self._player, self._opponent = self._opponent, self._player print("Player is: " + str(self._player)) print("Opponent is: " + str(self._opponent)) Raise an exception for an invalid move Increase its score by 1 Add a new piece for the current player Adjust pieces and scores for both players Iterate for all 8 directions Flip pieces in that direction Swap player and opponent Report results

16. Detailed design for the ReversiMC class Lastly, here is what the ReversiMC class needs to do Inherit features defined in the Reversi class Define the blocks used for the board itself: GOLD_BLOCK Keep track players: blocks and names 1 – “White”, white block 2 – “Black”, black block 0 – “None”, transparent block ( AIR ) Need the z coord for positioning Get move from the Minecraft game Output a message Display the results through Minecraft chat __init__(x,y,player) __init__(x,y,z,cols=8, rows=8) getMove(x,y,z,player) output(message) display() ReversiMC BOARD_MATERIAL = GOLD_BLOCK players=[AIR, Block(35, 0), Block(35, 15)] playerNames = ["None", "White", "Black"] Reversi

17. Initialize the class … class ReversiMC(Reversi): BOARD_MATERIAL = GOLD_BLOCK players = [AIR, Block(35, 0), Block(35, 15)] playerNames = ["None", "White", "Black"] def __init__(self,x,y,z,cols=8,rows=8): self._pos = Vec3(x,y,z) self._farcorner = Vec3(x+cols,y,z+rows) self._minecraft = Minecraft.create() self._minecraft.setBlocks(x,y-1,z,x+cols-1,y-1,z+rows-1, ReversiMC.BOARD_MATERIAL) self._minecraft.setBlocks(x,y,z,x+cols-1,y,z+rows-1, ReversiMC.players[0]) super(ReversiMC,self).__init__(cols,rows) Extend the base class Define global variables Use 3D library Choose blocks for players Connect to Minecraft Link to super class initialization

18. Getting move from Minecraft game def getMove(self): self.output("{0}'s move". format(ReversiMC.playerNames[self.nextPlayer()])) while True: # Note: only handle right-click events for now events = self._minecraft.events.pollBlockHits() for event in events: x,y,z = event.pos.x, event.pos.y, event.pos.z if self._pos.x <= x < self._farcorner.x and self._pos.z <= z < self._farcorner.z: return (x-self._pos.x, z-self._pos.z, self.nextPlayer()) time.sleep(0.1) Announce next player Minecraft gamer input Return as a list Validate move by checking space range Detect hit location Pause once for each game iteration Game loop until ended