Graphics Routines

The graphics routines were written for the final project based on the need for graphics in the user interaction in the game. These pocedures, variables, and data structures were written and designed by John Brumbaugh, unless otherwise stated.

• StoreBackground -- This function will be used to draw the main background for the game. It will just use String OpCodes to place the correct colors in the correct place in the ImageArray.

  ; ----------------------------------------------
  ; StoreBackground
  ;
  ; Inputs: None.
  ;
  ; Outputs: The contents of the image are stored directly in the ImageArray
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine is used instead of DOS Interrupts to place the
  ; background image into the ImageArray without having to load it from
  ; a file.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------

• StorePlayer1 -- This function will be used to draw the first player's image for the game. It will use String OpCodes to place the correct colors in the correct place within the ImageArray.

  ; ------------------------------------------------------
  ; StorePlayer1
  ;
  ; Inputs:None.
  ;
  ; Outputs: The contents of the image are stored directly to the ImageArray.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine is used instead of DOS Interrupts to place the image
  ; of the first player into the ImageArray without having to load the image from a
  ; file
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------

• StorePlayer2 -- This function will be used to draw the second player's image for the game. It will use String OpCodes to place the correct colors in the correct place within the ImageArray.

  ; ------------------------------------------------------
  ; StorePlayer2
  ;
  ; Inputs:None.
  ;
  ; Outputs: The contents of the image are stored directly to the ImageArray.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine is used instead of DOS Interrupts to place the image
  ; of the first player into the ImageArray without having to load the image from a
  ; file
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------

• DrawBackground -- This function will take the background image, which is the first element in the ImageArray and draw it to the BufferSeg. This is the first thing that will be drawn to the BufferSeg all the time.

  ; ------------------------------------------------------------
  ; DrawBackground
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine draws the background image directly to the BufferSeg.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• DrawUnit -- This function will draw the players on the screen. It will test to see if a player is active, and if he is draw him on the screen at the correct offset from the given row and column position. This will be drawn directly after the Background is placed into the BufferSeg.

  ; ------------------------------------------------------------
  ; DrawUnit
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: UnitArray -- The array that will store the different units
  ; in memory.
  ;
  ; Purpose: This routine will use the unit array and traverse through
  ; it and test to see if the unit is still alive, and if he is draw it at its
  ; current position. If the unit is DYING, draw the exploding BMP, and
  ; change is status to INACTIVE
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• SwapScreen -- This procedure will take all of the data in the BufferSeg and store it to the display.

  ; ------------------------------------------------------------
  ; SwapScreen
  ;
  ; Inputs: None.
  ;
  ; Outputs: Writes directly to the screen.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine is used for double buffering. This routine takes
  ; the BufferSeg and places all of its data directly to the Video Memory.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• ClearBuffer -- This procedure is used to clear the buffer before every buffer write. It is called within the DrawBackground procedure, to clear the buffer before the background is drawn to it.

  ; ------------------------------------------------------------
  ; ClearBuffer
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This routine clears the BufferSeg. It draws all Black to
  ; the entire BufferSeg
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• StoreAsteroid -- This procedure was used to draw the asteroid image to the ImageSeg in the appropriate offset in the ImageArray which was located in the ImageSeg

  ; ------------------------------------------------------------
  ; StoreAsteroid
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function places the Asteroid into the
  ; ImageArray using palette values and StringOps.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• StoreEnemy1 -- This procedure stores the first enemy type into the appropiate offset in the ImageArray which was located in the ImageSeg

  ; ------------------------------------------------------------
  ; StoreEnemy1
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function places the First Enemy into the
  ; ImageArray using palette values and StringOps.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• StoreEnemy2 -- This procedure stores the second enemy type into the appropiate offset in the ImageArray which was located in the ImageSeg

  ; ------------------------------------------------------------
  ; StoreEnemy2
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function places the Second Enemy into the
  ; ImageArray using palette values and StringOps.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• StoreExplosion -- This function will store the image of the explosion into the appropriate offset in the ImageArray which was loacted in the ImageSeg.

  ; ------------------------------------------------------------
  ; StoreEnemy2
  ;
  ; Inputs: None.
  ;
  ; Outputs: None.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function places the Second Enemy into the
  ; ImageArray using palette values and StringOps.
  ;
  ; Written by: John Brumbaugh
  ; -----------------------------------------------------------

• StorePCX -- This function reads a 320x200x256 color PCX file from disk and writes that data directly to a Mode 13h VGA Graphics screen

  ; ------------------------------------------------------------
  ; StorePCX
  ;
  ; Inputs: DX has the offset of the PCX filename to show; the
  ; PCX file is 320x200x256.
  ;
  ; Outputs: PCX file is displayed and all registers are
  ; restored to their original value.
  ;
  ; Input/Output: Nothing.
  ;
  ; Purpose: This function takes a PCX image and draws it to ; the screen.
  ;
  ; This function was originally written by Brandon Long, it
  ; was later modified by Eric Meidel and Nathan Jachimec.
  ; Their version of the code can be seen in the ECE 291 Lab
  ; Manual on pg. 117. For this project, this function was
  ; modified by John Brumbaugh -- brumbaug@uiuc.edu
  ; -----------------------------------------------------------

Graphics Constants

Below all the constants that are used by the grpahics routines are going to be described. Those descriptions will include the constants names, how they are used, and what they are equal to.

• VidGrSeg -- This is the constant equal to 0A000h used to access the Mode 13h VGA video screen with all the graphics routines.
• TextModeSeg -- This is the constant equal to 0B800 used to access the Text Mode Video screen in some of the graphics routines.

Graphics Structures

Below all the data structures that are used in the graphics routines are going to be described. In the descriptions, they will say what routines the structures are used in (graphics or others), what their format is, and what information will be a part of the structure.

PCX_HEADER STRUC   MANUFACTURER DB 10   VERSION DB ?   ENCODING DB 1    BITS_PER_PIXEL DB ?    XMIN DW ?    YMIN DW ?    XMAX DW ?    YMAX DW ?    PALETTE DB 48 DUP (?)    RESERVED DB ?    COLOR_PLANES DB ?    BYTES_PER_PLANE DW ?    PALETTE_TYPE DW ?    FILLER DB 58 DUP (?) PCX_HEADER ENDS

Graphics Segments

There will be two segments used by the graphics routines, one for double buffering and the other will be used to store the images after they have been loaded from the BMP files.

• BufferSeg -- This is the segment that all the graphics will be written to in the majority of the graphics routines. In the SwapBuffer routine, all data in the BufferSeg will be moved from the BufferSeg to be outputted directly to the screen.

  	BufferSeg SEGMENT PUBLIC
  	db 65535 dup (?)
  	BufferSeg ENDS

• ImageSeg -- This is the segment that will store all of the images used in the game from bullets, to players, to enemies, and even the background images. This segment will be accessed by the graphics routines when they are storing the BMP data. This segment will initially store 64 images of 2048 bytes that are entirely red.

  	ImageSeg SEGMENT PUBLIC
  	DB 64 DUP (2048 DUP (0))
  	ImageSeg ENDS

• ScratchSeg -- This segment is used when we load a PCX image. The data of the PCX image is stored into this segment and then manipulated from there.

  	ScratchSeg SEGMENT PUBLIC
  	ScratchPad DB 65535 DUP(?)
  	ScratchSeg ENDS