497 lines
20 KiB
Markdown
497 lines
20 KiB
Markdown
**LISTING 43.1 L43-1.ASM**
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; Program to demonstrate bit-plane animation. Performs
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; flicker-free animation with image transparency and
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; image precedence across four distinct planes, with
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; 13 32x32 images kept in motion at once.
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;
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;
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; Set to higher values to slow down on faster computers.
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; 0 is fine for a PC. 500 is a reasonable setting for an AT.
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; Slowing animation further allows a good look at
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; transparency and the lack of flicker and color effects
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; when images cross.
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;
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SLOWDOWN equ 10000
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;
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; Plane selects for the four colors we're using.
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;
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RED equ 01h
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GREEN equ 02h
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BLUE equ 04h
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WHITE equ 08h
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;
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VGA_SEGMENT equ 0a000h ;mode 10h display memory
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; segment
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SC_INDEX equ 3c4h ;Sequence Controller Index
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; register
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MAP_MASK equ 2 ;Map Mask register index in
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; Sequence Controller
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SCREEN_WIDTH equ 80 ;# of bytes across screen
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SCREEN_HEIGHT equ 350 ;# of scan lines on screen
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WORD_OUTS_OK equ 1 ;set to 0 to assemble for
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; computers that can't
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; handle word outs to
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; indexed VGA regs
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;
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stack segment para stack ‘STACK'
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db 512 dup (?)
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stack ends
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;
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; Complete info about one object that we're animating.
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;
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ObjectStructure struc
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Delay dw ? ;used to delay for n passes
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; throught the loop to
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; control animation speed
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BaseDelay dw ? ;reset value for Delay
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Image dw ? ;pointer to drawing info
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; for object
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XCoord dw ? ;object X location in pixels
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XInc dw ? ;# of pixels to increment
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; location by in the X
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; direction on each move
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XLeftLimit dw ? ;left limit of X motion
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XRightLimit dw ? ;right limit of X motion
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YCoord dw ? ;object Y location in pixels
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YInc dw ? ;# of pixels to increment
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; location by in the Y
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; direction on each move
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YTopLimit dw ? ;top limit of Y motion
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YBottomLimit dw ? ;bottom limit of Y motion
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PlaneSelect db ? ;mask to select plane to
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; which object is drawn
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db ? ;to make an even # of words
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; long, for better 286
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; performance (keeps the
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; following structure
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; word-aligned)
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ObjectStructure ends
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;
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Data segment word ‘DATA'
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;
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; Palette settings to give plane 0 precedence, followed by
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; planes 1, 2, and 3. Plane 3 has the lowest precedence (is
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; obscured by any other plane), while plane 0 has the
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; highest precedence (displays in front of any other plane).
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;
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Colors db 000h ;background color=black
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db 03ch ;plane 0 only=red
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db 03ah ;plane 1 only=green
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db 03ch ;planes 0&1=red (plane 0 priority)
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db 039h ;plane 2 only=blue
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db 03ch ;planes 0&2=red (plane 0 priority)
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db 03ah ;planes 1&2=green (plane 1 priority)
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db 03ch ;planes 0&1&2=red (plane 0 priority)
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db 03fh ;plane 3 only=white
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db 03ch ;planes 0&3=red (plane 0 priority)
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db 03ah ;planes 1&3=green (plane 1 priority)
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db 03ch ;planes 0&1&3=red (plane 0 priority)
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db 039h ;planes 2&3=blue (plane 2 priority)
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db 03ch ;planes 0&2&3=red (plane 0 priority)
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db 03ah ;planes 1&2&3=green (plane 1 priority)
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db 03ch ;planes 0&1&2&3=red (plane 0 priority)
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db 000h ;border color=black
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;
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; Image of a hollow square.
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; There's an 8-pixel-wide blank border around all edges
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; so that the image erases the old version of itself as
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; it's moved and redrawn.
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;
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Square label byte
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dw 48,6 ;height in pixels, width in bytes
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rept 8
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db 0,0,0,0,0,0;top blank border
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endm
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.radix 2
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,00000000,00000000,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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db 0,11111111,11111111,11111111,11111111,0
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.radix 10
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rept 8
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db 0,0,0,0,0,0;bottom blank border
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endm
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;
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; Image of a hollow diamond with a smaller diamond in the
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; middle.
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; There's an 8-pixel-wide blank border around all edges
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; so that the image erases the old version of itself as
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; it's moved and redrawn.
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;
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Diamond label byte
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dw 48,6 ;height in pixels, width in bytes
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rept 8
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db 0,0,0,0,0,0;top blank border
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endm
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.radix 2
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db 0,00000000,00000001,10000000,00000000,0
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db 0,00000000,00000011,11000000,00000000,0
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db 0,00000000,00000111,11100000,00000000,0
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db 0,00000000,00001111,11110000,00000000,0
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db 0,00000000,00011111,11111000,00000000,0
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db 0,00000000,00111110,01111100,00000000,0
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db 0,00000000,01111100,00111110,00000000,0
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db 0,00000000,11111000,00011111,00000000,0
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db 0,00000001,11110000,00001111,10000000,0
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db 0,00000011,11100000,00000111,11000000,0
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db 0,00000111,11000000,00000011,11100000,0
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db 0,00001111,10000001,10000001,11110000,0
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db 0,00011111,00000011,11000000,11111000,0
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db 0,00111110,00000111,11100000,01111100,0
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db 0,01111100,00001111,11110000,00111110,0
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db 0,11111000,00011111,11111000,00011111,0
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db 0,11111000,00011111,11111000,00011111,0
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db 0,01111100,00001111,11110000,00111110,0
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db 0,00111110,00000111,11100000,01111100,0
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db 0,00011111,00000011,11000000,11111000,0
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db 0,00001111,10000001,10000001,11110000,0
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db 0,00000111,11000000,00000011,11100000,0
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db 0,00000011,11100000,00000111,11000000,0
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db 0,00000001,11110000,00001111,10000000,0
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db 0,00000000,11111000,00011111,00000000,0
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db 0,00000000,01111100,00111110,00000000,0
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db 0,00000000,00111110,01111100,00000000,0
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db 0,00000000,00011111,11111000,00000000,0
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db 0,00000000,00001111,11110000,00000000,0
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db 0,00000000,00000111,11100000,00000000,0
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db 0,00000000,00000011,11000000,00000000,0
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db 0,00000000,00000001,10000000,00000000,0
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.radix 10
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rept 8
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db 0,0,0,0,0,0; bottom blank border
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endm
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;
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; List of objects to animate.
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;
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even;word-align for better 286 performance
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;
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ObjectListlabelObjectStructure
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ObjectStructure <1,21,Diamond,88,8,80,512,16,0,0,350,RED>
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ObjectStructure <1,15,Square,296,8,112,480,144,0,0,350,RED>
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ObjectStructure <1,23,Diamond,88,8,80,512,256,0,0,350,RED>
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ObjectStructure <1,13,Square,120,0,0,640,144,4,0,280,BLUE>
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ObjectStructure <1,11,Diamond,208,0,0,640,144,4,0,280,BLUE>
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ObjectStructure <1,8,Square,296,0,0,640,144,4,0,288,BLUE>
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ObjectStructure <1,9,Diamond,384,0,0,640,144,4,0,288,BLUE>
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ObjectStructure <1,14,Square,472,0,0,640,144,4,0,280,BLUE>
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ObjectStructure <1,8,Diamond,200,8,0,576,48,6,0,280,GREEN>
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ObjectStructure <1,8,Square,248,8,0,576,96,6,0,280,GREEN>
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ObjectStructure <1,8,Diamond,296,8,0,576,144,6,0,280,GREEN>
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ObjectStructure <1,8,Square,344,8,0,576,192,6,0,280,GREEN>
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ObjectStructure <1,8,Diamond,392,8,0,576,240,6,0,280,GREEN>
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ObjectListEndlabelObjectStructure
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;
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Dataends
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;
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; Macro to output a word value to a port.
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;
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OUT_WORDmacro
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if WORD_OUTS_OK
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out dx,ax
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else
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out dx,al
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inc dx
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xchg ah,al
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out dx,al
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dec dx
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xchg ah,al
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endif
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endm
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;
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; Macro to output a constant value to an indexed VGA
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; register.
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;
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CONSTANT_TO_INDEXED_REGISTERmacro ADDRESS, INDEX, VALUE
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movdx, ADDRESS
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movax, (VALUE shl 8) + INDEX
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OUT_WORD
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endm
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;
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Code segment
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assume cs:Code, ds:Data
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Start proc near
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cld
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mov ax, Data
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mov ds, ax
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;
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; Set 640x350 16-color mode.
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;
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mov ax,0010h ;AH=0 means select mode
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;AL=10h means select
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; mode 10h
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int 10h ;BIOS video interrupt
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;
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; Set the palette up to provide bit-plane precedence. If
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; planes 0 & 1 overlap, the plane 0 color will be shown;
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; if planes 1 & 2 overlap, the plane 1 color will be
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; shown; and so on.
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;
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mov ax,(10h shl 8) + 2 ;AH = 10h means
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; set palette
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; registers fn
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;AL = 2 means set
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; all palette
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; registers
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push ds ;ES:DX points to
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pop es ; the palette
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mov dx,offset Colors ; settings
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int 10h ;call the BIOS to
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; set the palette
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;
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; Draw the static backdrop in plane 3. All the moving images
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; will appear to be in front of this backdrop, since plane 3
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; has the lowest precedence the way the palette is set up.
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;
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CONSTANT_TO_INDEXED_REGISTER SC_INDEX, MAP_MASK, 08h
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;allow data to go to
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; plane 3 only
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;
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; Point ES to display memory for the rest of the program.
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;
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mov ax,VGA_SEGMENT
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mov es,ax
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;
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sub di,di
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mov bp,SCREEN_HEIGHT/16 ;fill in the screen
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; 16 lines at a time
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BackdropBlockLoop:
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call DrawGridCross ;draw a cross piece
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call DrawGridVert ;draw the rest of a
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; 15-high block
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dec bp
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jnz BackdropBlockLoop
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call DrawGridCross ;bottom line of grid
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;
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; Start animating!
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;
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AnimationLoop:
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mov bx,offset ObjectList ;point to the first
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; object in the list
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;
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; For each object, see if it's time to move and draw that
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; object.
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;
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ObjectLoop:
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;
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; See if it's time to move this object.
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;
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dec [bx+Delay] ;count down delay
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jnz DoNextObject ;still delaying-don't move
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mov ax,[bx+BaseDelay]
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mov [bx+Delay],ax ;reset delay for next time
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;
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; Select the plane that this object will be drawn in.
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;
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mov dx,SC_INDEX
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mov ah,[bx+PlaneSelect]
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mov al,MAP_MASK
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OUT_WORD
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;
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; Advance the X coordinate, reversing direction if either
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; of the X margins has been reached.
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;
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mov cx,[bx+XCoord] ;current X location
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cmp cx,[bx+XLeftLimit] ;at left limit?
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ja CheckXRightLimit ;no
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neg [bx+XInc] ;yes-reverse
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CheckXRightLimit:
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cmp cx,[bx+XRightLimit] ;at right limit?
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jb SetNewX ;no
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neg [bx+XInc] ;yes-reverse
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SetNewX:
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add cx,[bx+XInc] ;move the X coord
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mov [bx+XCoord],cx ; & save it
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;
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; Advance the Y coordinate, reversing direction if either
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; of the Y margins has been reached.
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;
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mov dx,[bx+YCoord] ;current Y location
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cmp dx,[bx+YTopLimit] ;at top limit?
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ja CheckYBottomLimit ;no
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neg [bx+YInc] ;yes-reverse
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CheckYBottomLimit:
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cmp dx,[bx+YBottomLimit] ;at bottom limit?
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jb SetNewY ;no
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neg [bx+YInc] ;yes-reverse
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SetNewY:
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add dx,[bx+YInc] ;move the Y coord
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mov [bx+YCoord],dx ; & save it
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;
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; Draw at the new location. Because of the plane select
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; above, only one plane will be affected.
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;
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mov si,[bx+Image] ;point to the
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; object's image
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; info
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call DrawObject
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;
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; Point to the next object in the list until we run out of
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; objects.
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;
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DoNextObject:
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add bx,size ObjectStructure
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cmp bx,offset ObjectListEnd
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jb ObjectLoop
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;
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; Delay as specified to slow things down.
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;
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if SLOWDOWN
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mov cx,SLOWDOWN
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DelayLoop:
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loop DelayLoop
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endif
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;
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; If a key's been pressed, we're done, otherwise animate
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; again.
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;
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CheckKey:
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mov ah,1
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int 16h ;is a key waiting?
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jz AnimationLoop ;no
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sub ah,ah
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int 16h ;yes-clear the key & done
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;
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; Back to text mode.
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;
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mov ax,0003h ;AL=03h means select
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; mode 03h
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int 10h
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;
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; Back to DOS.
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;
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mov ah,4ch ;DOS terminate function
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int 21h ;done
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;
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Start endp
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;
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; Draws a single grid cross-element at the display memory
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; location pointed to by ES:DI. 1 horizontal line is drawn
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; across the screen.
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;
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; Input: ES:DI points to the address at which to draw
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;
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; Output: ES:DI points to the address following the
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; line drawn
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;
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; Registers altered: AX, CX, DI
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;
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DrawGridCross proc near
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mov ax,0ffffh ;draw a solid line
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mov cx,SCREEN_WIDTH/2-1
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rep stosw ;draw all but the rightmost
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; edge
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mov ax,0080h
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stosw ;draw the right edge of the
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; grid
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ret
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DrawGridCross endp
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;
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; Draws the non-cross part of the grid at the display memory
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; location pointed to by ES:DI. 15 scan lines are filled.
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;
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; Input: ES:DI points to the address at which to draw
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;
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; Output: ES:DI points to the address following the
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; part of the grid drawn
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;
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; Registers altered: AX, CX, DX, DI
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;
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DrawGridVert proc near
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mov ax,0080h ;pattern for a vertical line
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mov dx,15 ;draw 15 scan lines (all of
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; a grid block except the
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; solid cross line)
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BackdropRowLoop:
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mov cx,SCREEN_WIDTH/2
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rep stosw ;draw this scan line's bit
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; of all the vertical lines
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; on the screen
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dec dx
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jnz BackdropRowLoop
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ret
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DrawGridVert endp
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;
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; Draw the specified image at the specified location.
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; Images are drawn on byte boundaries horizontally, pixel
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; boundaries vertically.
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; The Map Mask register must already have been set to enable
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; access to the desired plane.
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;
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; Input:
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; CX - X coordinate of upper left corner
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; DX - Y coordinate of upper left corner
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; DS:SI - pointer to draw info for image
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; ES - display memory segment
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;
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; Output: none
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;
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; Registers altered: AX, CX, DX, SI, DI, BP
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;
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DrawObject proc near
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mov ax,SCREEN_WIDTH
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mul dx ;calculate the start offset in
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; display memory of the row the
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; image will be drawn at
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shr cx,1
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shr cx,1
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shr cx,1 ;divide the X coordinate in pixels
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; by 8 to get the X coordinate in
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; bytes
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add ax,cx ;destination offset in display
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; memory for the image
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mov di,ax ;point ES:DI to the address to
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; which the image will be copied
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; in display memory
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lodsw
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mov dx,ax ;# of lines in the image
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lodsw ;# of bytes across the image
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mov bp,SCREEN_WIDTH
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subbp,ax ;# of bytes to add to the display
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; memory offset after copying a line
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; of the image to display memory in
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; order to point to the address
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; where the next line of the image
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; will go in display memory
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DrawLoop:
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mov cx,ax ;width of the image
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rep movsb ;copy the next line of the image
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; into display memory
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add di,bp ;point to the address at which the
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; next line will go in display
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; memory
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dec dx ;count down the lines of the image
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jnzDrawLoop
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ret
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DrawObjectendp
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;
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Code ends
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end Start
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