Implementation

The game is broken down into five major parts: AI, gameplay/game engine, 2D animation, 2D graphics, sound.  We are trying for an AI that gets progressively harder based on difficulty and level, also showing the different "personalities" of each ghost.  The gameplay/game engine consists of the interface with the keyboard and mouse, and the logic behind the movement of the characters in the game.  To make the game look more continuous, 2D animation must be used.  Using PCX files and 2D graphics procedures, we load the images of our game from files, then translate it to a playable map based on data maps.  This also allows other PCX file images to be used so that we can easily change what the pieces of the game look like.  We will use SoundBlaster sound effects, and also MIDI quality music to improve the general gameplay. One neat feature of our game is the addition of a Board Editor. It allows the user to create his or her own levels.

2D Graphics The moveable components of the game (i.e. ghosts, pacman, fruit), work on a continuous X,Y basis.  The non-moving components use a Board array that works in a "block" format.  The DataArray consists of numbers telling the engine what to display at that "block" (our gameboard is 20x20 blocks).  The moveable components can move within blocks however, to simulate animation, and so that pacman doesn't have to be exactly on a block to be killed by or to eat a ghost.  Continuous X,Y is the same as the pixel value, so unlike the blocks, the moveable components can have 320x200 values.  There will be a constant step value for pacman and fruit, because they will probably move more than 1 pixel at a time.  There is also a ghost step value, but this changes with difficulty and level, thus simulating a faster ghost.

Team Members

• Raymond Chen - AI, Gameplay
• David Ripley - 2D Animation/Graphics
• Rob Yepez - 2D Graphics, PCX Development/Implementation
• Chris McGlone - 2D Graphics, Gameplay
• Daryl Kowalski - Sound and Music

Constants
 
Constants relating to board and block dimensions:

BOARDEDGE       EQU 60
BLOCKDIM        EQU 10
BOARDDIM        EQU 20
OVERLAP         EQU 2

Movement constants:

GOUP            EQU 0
GORIGHT         EQU 1
GODOWN          EQU 2
GOLEFT          EQU 3

Look-Up Tables

DeltaFruitX - change in x coordinates for indexed direction
DeltaFruitY - change in y coordinates for indexed direction
Intersection - table containing values of intersections
DeltaBlockX - block x-coordinate change
DeltaBlockY - block y-coordinate change
DeltaPacX - Change in pacman's pixel x-coordinate
DeltaPacY - Change in pacman's pixel y-coordinate
DeltaGstX - Change in ghost pixel x-coordinate
DeltaGstY - Change in ghost pixel y-coordinate
WarpX - Change in x-coordinate of warping
WarpY - Change in y-coordinate of warping
OpDirTable - opposite direction lookup table
OpAxisDir - opposite axis diections
GhostTimer - lookup table to see when ghosts leave the box
Method - Computer AI lookup table based on difficulty and personality
FruitScoreIndex - index for offsets of fruit score
GhostScoreIndex - index for offsets of ghost score
 
 

Global Variables

The procedures of the game input and output, primarily global variables.  This is the list of variables used by our game:

WORD GhostX - array of the four ghost X-positions
WORD GhostY - array of the four ghost Y-positions
WORD PacX - X-position of Pacman
WORD PacY - Y-position of Pacman
WORD FruitX - X-position of fruit/bonus piece
WORD FruitY - Y-position of fruit/bonus piece
WORD FruitDir - angle/direction of Fruit movement
WORD PacDir - View angle/direction Pacman is facing
WORD GhostDir - array of the four ghost view angles
WORD BoardLocation - Offset of the DataArray
WORD PacState - current state of pacman (animation of pacman opening and closing mouth)
WORD LevelData - array of offsets pointing to filenames of each level's map data
WORD TotalPellets - Total pellets on the current board
WORD Pelletsleft - number of pellets left on the current level
WORD GhostSelect - flags which ghost is being controlled by the second player
WORD Randval - random value seed
WORD MemLoc - 20-bit linear address used by sound procedure
DOUBLE EngineCycles - numebr of mainloop iterations for the current level
BYTE   Pause_Flag - flag determining when game is paused
BYTE   Quit - flag for quitting of game
BYTE   PacLives - Number of lives left
BYTE   MoveBuffer1 - next move pacman will make
BYTE   MoveBuffer2 - next move the selected ghost will make
BYTE   PowerPelletFlag - array of flags determining when and which ghosts are vunerable
BYTE   GhostData - array that holds information about ghost AI
BYTE   GhostStep - translates to the "speed" of the ghosts, which changes throughout the game
BYTE   BlockPX - block X-position of pacman
BYTE   BlockPY - block Y-position of pacman
BYTE   Gamedata - string holding filename of TextSeg file
BYTE   DelayC - Delay Consant
BYTE   Length1 - length of file for sound procedure

Segments

SBSeg: screen buffer segment -> outputs directly to screen
LevelSeg: wall, pellet element segments (changes per level)
ScratchSeg: scratch segment (used by LoadPCX)
TextSeg: textures segment, containing ghost, pacman, and fruit images

Procedures

Gameplay/Game Engine

InstKey/GameKeyInt/DeinstKey

• Author: Rob Yepez
• Inputs: button press
• Outputs: Quit, Pause_Flag, MoveBuffer1, MoveBuffer2, GhostSelect
• Description: Replaces default keyboard interrupt routine
• Assumptions: Quit, Pause_Flag are flags showing the state of the game.  MoveBuffer 1 and 2 output according to a direction table.  GhostSelect is changed as the 2nd player TABs through the ghosts.

Mouse_Control

• Author: Rob Yepez
• Inputs: Mouse
• Outputs: Two_Player, One_Player, Quit
• Calls: LoadPCX, ShowScreenBuffer
• Description: Checks location of mouse cursor on screen to see if it is over a valid button, then loads a toggled button image and outputs it to the screen.

MoveGhost

• Author: Ray Chen
• Inputs: GhostX, GhostY, GhostDir, GhostData, GhostStep, PowerPelletFlag, MoveBuffer2
• Outputs: GhostX, GhostY, GhostDir
• Description: This procedure takes the current position, direction, and attempt for next move (which is contained in GhostData) and changes the position accordingly.  This procedure must check for valid moves for each of the ghosts, and if a 2nd player is controlling a ghost, then the move which is given by GhostData is overridden by the players input.  GhostStep is not actually changed by this procedure, but evaluated in conjunction with PowerPelletFlag to determine how far the ghosts move.  GhostX, GhostY, and GhostDir are updated and outputed.

MovePacMan

• Author: Chris McGlone
• Inputs: PacX, PacY, PacDir, MoveBuffer1, PacState
• Outputs: PacX, PacY, PacDir, PacState
• Description: This procedure takes the current position and direction of pacman and determines if it can move, and how it moves based on the control of the player.  PacState is changed if pacman moves, thus animating the eating of pacman.  PacX, PacY, PacDir, and PacState are updated and outputed.

CalcBlockRound

• Author: Ray Chen
• Inputs: cx - x-coordinate(pixel), dx - y-coordinate(pixel)
• Outputs: al - x-coordinate(block), ah - y-coordinate(block)
• Description: This procedure converts continuous coordinates to 10x10 block coordinates

GetBoardValue

• Author: Chris McGlone
• Inputs: al - block x-position, ah -block y-position
• Outputs: bx - board value at block X, block Y
• Description: This procedure takes a block position within the board then looks up Board array to see what kind of block occupys that position.

PutBoardValue

• Author: Chris McGlone
• Inputs: al - block x-pos, ah - block y-pos, bx - value
• Outputs: Board
• Description: Takes a block x and y position (al,ah), and puts the value in bx into the board array at that position.

BlockXY

• Author: Ray Chen
• Inputs: cx - x-coordinate, dx - y-coordinate
• Outputs: BlockXY
• Description: takes continuous x and y coordinates and tells if it is in a column, row, or both

ExitGhost

• Author: Ray Chen
• Inputs: GhostX, GhostY, EngineCycles, GhostBox, GhostTimer
• Outputs: GhostDir, GhostY, GhostBox
• Description: Checks if ghosts are in box then moves them out of box depending on values in GhostTimer and EngineCycles.

SetUpGameData

• Author: Chris McGlone
• Inputs: GameData
• Outputs: TextSeg
• Calls: LoadPCX
• Description: Loads general textures into TextSeg

InitHighScore

• Author: Chris McGlone
• Inputs: InitHigh
• Description: This procedure initializes the high score file to the InitHigh variable.

ChangePacState

• Author: Chris McGlone
• Inputs: PacState, PAcStateDir
• Outputs: PacState
• Description: calculates the next appropriate state of pacman.

SetUpLevelData

• Author: Chris McGlone
• Inputs: LevelData, BoardLocation
• Outputs: GhostStep, GhostX, GhostY, PacX, PacY, PelletsLeft, DataArray
• Calls: LoadPCX, DrawArray, DrawGhost, DrawPacman
• Description: Initializes level by intializing starting ghost and pacman positions, filling DataArray with the data from the level's data file. Initializes PelletsLeft, and GhostStep based on level.

CheckArray

• Author: Chris McGlone
• Inputs: BoardLocation, PacX, PacY
• Outputs: DataArray, PowerPelletFlag, PelletsLeft
• Description: Updates contents of DataArray, based on when Pacman has fully entered a new block (i.e. his continuous position is equal to that of a block).  Then it updates PelletsLeft if a pellet is eaten, and PowerPelletFlag if a power pellet is eaten as well.

2D Animation

Pacman_Death

• Author: Rob Yepez
• Inputs: AX - offset of block where animation takes place
• Calls: ShowScreenBuffer
• Description: Animate Pacman's brutal demise.

Ghost_Death

• Author: Rob Yepez
• Inputs: AX - offset of block where animation takes place
• Calls: ShowScreenBuffer, DrawRectangle, ClearScreenBuffer, DrawArray, DrawScore, DrawPacLife, DrawPacKill, DrawFruitLevel, Delay
• Description: Animation of ghost's death.

Fruit_Death

• Author: Rob Yepez
• Inputs: AX - offset
• Calls: ShowScreenBuffer
• Description: eating of fruit

CheckDeath

• Author: Rob Yepez
• Inputs: PowerPelletFlag, GhostX, GhostY, FruitX, FruitY, PacX, PacY
• Outputs: GhostX, GhostY, PowerPelletFlag, FruitX, FruitY, PacX, PacY
• Calls: PlaySequence, Ghost_death, Pac_death, Fruit_Death
• Description: Check who dies and if powerpelletflag is on the ghost dies, otherwise pacman dies, clears flag if necessary.

DrawPacman

• Author: David Ripley
• Inputs: PacState, PacDir, PacX, PacY, TextSeg
• Outputs: DI - offset of place to be drawn in ScreenBuffer, SI - Offset in the Textseg to access
• Calls: DrawBlock
• Description: Calculates the top left offset position in ScreenBuffer of the block of pacman to be drawn based on PacX and PacY (outputs into SI).  The proper texture offset is calculated through a lookup table and is based on PacState and PacDir (outputs into DI).

DrawGhost

• Author: David Ripley
• Inputs: GhostX, GhostY, GhostDir, PowerPelletFlag, GhostSelect, TextSeg
• Outputs: DI - offset of place to be drawn in ScreenBuffer, SI - offset in the TextSeg to access
• Calls: DrawBlock
• Description: This procedure works much the same as DrawPacman with respect to the offset of the ScreenBuffer(SI output).  The offset of the texture segment is calculated based on GhostDir, PowerPelletFlag, and GhostSelect, because not only are there different eye directions, but a different color for vulnerable ghosts, and when a ghost is being controlled by a 2nd player, it is another color as well.  This process is looped through four times, for each of the ghosts, with DrawBlock being called four times.

DrawFruit

• Author: David Ripley
• Inputs: FruitX, FruitY, Level
• Outputs: DI - offset of the place to be drawn in ScreenBuffer, SI - offset in the TextSeg to access
• Calls: DrawBlock
• Description: Same as above procedures for the calculation of SI, but DI is based on the level.

2D Graphics

Introduction

• Author: Rob Yepez
• Calls: IntroMouseControl, IntroductionAnimation, ClearScreenBuffer, DrawIntroScreen, ShowScreenBuffer
• Description: Displays the introduction screen and menu, then calls Mouse_Control and waits for selection of a valid option.

ExitDisplay

• Calls: LoadPCX, ShowScreenBuffer
• Description: Displays credit/exit screen when game is exited.

DrawScore

• Author: Chris McGlone
• Inputs: P1Score, P2Score, HiScore, Ghost Select
• Outputs: ScreenBuffer
• Calls: DrawRectangle, DrawDigits
• Description: draws the appropriate scores to screen buffer depending on play mode

DrawDigits

• Author: Chris McGlone
• Inputs: si, di
• Outputs: ScreenBuffer
• Calls: DrawRectangle
• Description: Draws the proper digit to the inputed offset.

DrawPacLife

• Author: David Ripley
• Inputs: PacLives
• Outputs: screen
• Calls: DrawRectangle
• Description: Draws an image of pacman to the bottom left of the screen for each life that pacman has in addition to the one pacman is using.

DrawFruitLevel

• Author: David Ripley
• Inputs: Level, TextSeg
• Outputs: screen
• Calls: DrawRectangle
• Description: All of the fruits that have appeared for each level played and including the present level are shown on the screen to the left of the board.  Hence, the number of fruits shown will be equal to the present level.

DrawBlockPart

• Author: Chris McGlone
• Inputs: bx, si, di
• Outputs: ScreenBuffer
• Description: Draws given number of lines of specified texture into screen buffer. si = offset of texture in text seg, di = offset to print in SBseg, bx = number of lines to print

DrawBoardPart

• Author: Chris McGlone
• Inputs: si - offset of board part in texture segment, di - offset of destination in screen buffer
• Output: ScreenBuffer
• Description: Draws a part of the board from the texture segment into the screen buffer.

DrawArray

• Author: Chris McGlone
• Inputs: BoardLocation, LevelSeg
• Output: screen
• Calls: ShowScreenBuffer
• Description: Draws static board elements from LevelSeg to ScreenBuffer, based on contents of the DataArray.

DrawPacKills

• Author: David Ripley
• Inputs: PacLives
• Outputs: screen
• Calls: DrawRectangle
• Description: When pacman dies, print an image of pacman with an 'X', through him, to the bottom right of the screen.  Only do this when in two player mode.  The number of images that are on the screen at any one time should equal the number of deaths of Pacman.

DrawRectangle

• Author: Chris McGlone
• Inputs: ax - segment, cx - width, dx - height, si - offset of texture, di - offset of screenbuffer
• Outputs: ScreenBuffer
• Description: Draws a rectangular picture in screenbuffer from the texture (for any non-square block)

DrawBlock

• Author: David Ripley
• Inputs: DI, SI, SBSeg, TextSeg
• Outputs: ScreenBuffer
• Description: To draw a block from the texture segment to the screen buffer segment.  SI: source offset, DI: destination offset.
• Notes: This procedure is called by DrawPacman, DrawGhost, DrawFruit.  The texture drawn into ScreenBuffer is a block.  Transparent pixels will be used to draw only the part of the block containing actual ghost, pacman, or fruit.

ClearScreenBuffer

• Author: Chris McGlone
• Outputs: ScreenBuffer
• Description: Clears the screen buffer.

ShowScreenBuffer

• Author: David Ripley
• Inputs: SBSeg, ScreenBuffer
• Outputs: screen
• Description: Draws ScreenBuffer to screen.

LoadPCX

• Author: David Ripley
• Inputs: AX, DX
• Outputs: DestSeg, ScratchSeg
• Description: Loads PCX image into a VGA segment.
• Notes: AX = Destination segment address, DX = pointer to a null-terminated string containing the filename


 

Artificial Intelligence

ComputeAI

• Author: Ray Chen
• Inputs: PowerPelletFlag, Difficulty
• Outputs: GhostData
• Calls: BlockPosition
• Description: This procedure calls BlockPosition to get the block X,Y positions of the ghosts and pacman.  Based on the positions, difficulty, level, and the powerpelletflag, the next movements of the ghosts are generated and outputed to GhostData.

Sound and Music

RegisterXmidi

• Author: Daryl Kowalski
• Inputs: AX - Command number, BX - offset of far address of XMIDI, CX - segment of far address of XMIDI, SI - low word of length XMIDI, DI - High word of length XMIDI
• Outputs: AX
• Description: Registers an AXMIDI file by address for playback. AX = 0 if unable to register XMIDI data, and 1 when registered resident

PlaySequence

• Author: Daryl Kowalski
• Inputs: AX - Command Number, BX - Sequence number to be played
• Outputs: AX
• Description: Plays selected WAV sound based on position and situation of pacman and/or ghosts.  AX = 1 when sequence is being played and 0 when sequence is not available.
• Notes: Called whenever pacman is in a situation requiring sound.

MidiStop

• Author: Daryl Kowalski
• Inputs: AX - Command number
• Description: Procedure is called to stop playing the current MIDI sequence.

ResumePlaying

• Author: Daryl Kowalski
• Inputs: AX - Command number
• Description: Resume PLaying stopped sequence.

Board Editor Procedures

CalcCursorBlock

• Author: Chris McGlone
• Inputs: cx - x-position of cursor, dx- y-position of cursor
• Outputs: al - block-x position, ah- block-y position
• Description: Calculates the block position of the cursor based on the continuous x and y coordinates.

EditMouseControl

• Author: Rob Yepez
• Outputs: BoardBE - Flag indicating board was clicked, SaveBE - flag indicating SaveBoard, ClearBE - Clear editor flag, ExitBE- exit editor flag, BlockBE- block was clicked flag, AX - tile that was clicked
• Description: This procedure gets the input from the user via mouse and sets the proper flags for processing as indicated above.

DrawEditor

• Author: Rob Yepez
• Calls: DrawArray, DrawBoardPart
• Description: Draws the editor screen, with buttons and tiles.

BoardEditor

• Author: Chris McGlone
• Input: custom_file
• Calls: ClearScreenBuffer, DrawEditor, ShowScreenBuffer, EditMouseControl, CalcCursorBlock, PutBoardValue
• Description: This procedure allows the user to design and save custtom board file.  Control loop for the board editor.

General Procedures

RandVal

• Author: Ray Chen
• Inputs: Randval
• Outputs: AX - random number, Randval- next value seed
• Description: Takes a random seed and computes a random value.

Delay

• Author: Rob Yepez
• Inputs: DelayC
• Description: Wastes CPU cycles.  Delays DelayX*AFFFh cycles.

DefineCustom

• Author: Chris McGlone
• Description: Clears the board array and writes ocntents of clear board array to clear board file.

IntroMouseControl

• Author: Rob Yepez
• Outputs: CX, DX
• Calls: DrawIntroButton
• Description: Gets user input via mouse and does a toggle

DrawIntroScreen

• Author: Rob Yepez
• Outputs: screen
• Calls: DrawIntroButton, ClearScreenBuffer
• Description: Displays the intro menu.

DrawIntroButton

• Author: Rob Yepez
• Inputs: si, di
• Outputs: es
• Description: Draws button to video segment.

IntroductionAnimation

• Author: Rob Yepez
• Outputs: screen
• Description: Animates pacmand and ghost for introduction opening.

DrawIntroImages

• Author: Rob Yepez
• Inputs: si, di
• Outputs: es
• Description: Draw ghost or pacman to segment and check for bounds.

CreditAnimation

• Author: Rob Yepez
• Outputs: screen
• Description: Animates the credit screen

DrawCreditImages

• Author: Rob Yepez
• Inputs: si, di
• Outputs: es
• Description: Draws credits from bottom to top and must check for bounds.

Credits

• Author: Rob Yepez
• Outputs: screen
• Calls: IntroMouseControl, IntroductionAnimation, ClearScreenBuffer, DrawIntroScreen, ShowScreenBuffer
• Description: This procedure displays the animation and credits.