363 lines
6.6 KiB
ArmAsm
363 lines
6.6 KiB
ArmAsm
.include "zp.inc"
|
|
|
|
;===========
|
|
; CONSTANTS
|
|
;===========
|
|
|
|
NUMSTARS EQU 16
|
|
|
|
|
|
;=====================
|
|
; Starfield
|
|
;=====================
|
|
|
|
;================================
|
|
; Clear screen and setup graphics
|
|
;================================
|
|
|
|
jsr clear_screens ; clear top/bottom of page 0/1
|
|
jsr set_gr_page0
|
|
|
|
; Initialize the 2kB of multiply lookup tables
|
|
jsr init_multiply_tables
|
|
|
|
|
|
;===============
|
|
; Init Variables
|
|
;===============
|
|
lda #0 ; 2
|
|
sta DRAW_PAGE ; 3
|
|
sta RANDOM_POINTER ; 3
|
|
|
|
ldy #(NUMSTARS-1) ; 2
|
|
init_stars:
|
|
jsr random_star ; 6
|
|
dey ; 2
|
|
bpl init_stars ; 2nt/3
|
|
|
|
;===========================
|
|
;===========================
|
|
; Main Loop
|
|
;===========================
|
|
;===========================
|
|
|
|
starfield_loop:
|
|
|
|
;===============
|
|
; clear screen
|
|
;===============
|
|
jsr clear_top ; 6+
|
|
; 6047
|
|
;===============
|
|
; draw stars
|
|
;===============
|
|
|
|
|
|
; start at 15 and count down (rather than 0 and count up)
|
|
ldx #(NUMSTARS-1)
|
|
|
|
draw_stars:
|
|
stx XX
|
|
|
|
;================
|
|
; calculate color
|
|
;================
|
|
|
|
lda #$ff ; want if z<16, color = 5
|
|
sta COLOR ; if 16<z<32 color = 13
|
|
; if 32<z<64 color = 15
|
|
ldy XX
|
|
lda star_z,Y
|
|
tay ; put star_z[i] in Y for later
|
|
|
|
cmp #32
|
|
bpl done_color
|
|
|
|
cmp #16 ; 15 -1 16 0 17 1
|
|
bpl second_color
|
|
|
|
lda #$55
|
|
sta COLOR
|
|
|
|
jmp done_color
|
|
second_color:
|
|
lda #$dd
|
|
sta COLOR
|
|
|
|
done_color:
|
|
|
|
|
|
; calculate x value, stars[i].x/stars[i].z
|
|
|
|
; put 1/stars[i].z in NUM1H:NUM1L and multiply
|
|
|
|
lda z_table,Y
|
|
sta NUM1L ; F
|
|
|
|
; adjust for 58+
|
|
; all this logic to avoid having a 128 byte table of mostly zero
|
|
lda #0 ; I
|
|
clc
|
|
cpy #60 ; 59 -1 60 0 61 1
|
|
bmi no_adjust
|
|
adc #1 ; 60, 61 = 1
|
|
cpy #62 ; 61 -1 62 0 63 1
|
|
bmi no_adjust
|
|
adc #1 ; 62 = 2
|
|
cpy #63 ; 62 = -1 63 = 0 64 = not possible
|
|
bne no_adjust
|
|
adc #2 ; 63 = 4
|
|
no_adjust:
|
|
sta NUM1H
|
|
|
|
; load stars[i].x into NUM2H:NUM2L
|
|
; NUM2L is always zero
|
|
ldy XX
|
|
|
|
lda star_x,Y
|
|
sta NUM2H
|
|
|
|
lda #0
|
|
sta NUM2L
|
|
sec ; don't reuse old values
|
|
jsr multiply
|
|
|
|
; integer result in X
|
|
txa
|
|
clc
|
|
adc #20
|
|
|
|
sta XPOS
|
|
|
|
; calculate y value, stars[i].y/stars[i].z
|
|
|
|
; 1/stars[i].z is still in NUM1H:NUM1L
|
|
|
|
ldy XX
|
|
|
|
lda star_y,Y
|
|
sta NUM2H
|
|
lda #0
|
|
sta NUM2L
|
|
clc ; reuse old values
|
|
jsr multiply
|
|
|
|
; integer result in X
|
|
txa
|
|
clc
|
|
adc #20
|
|
|
|
tay ; Y is YPOS
|
|
sty YPOS ; put Y value in Y to plot
|
|
|
|
|
|
;============================
|
|
; Check Limits
|
|
;============================
|
|
|
|
lda XPOS
|
|
bmi new_star
|
|
cmp #40
|
|
bpl new_star
|
|
|
|
ldy YPOS
|
|
bmi new_star
|
|
cpy #40
|
|
bpl new_star
|
|
|
|
; FIXME: sort out all of these jumps to be more efficient
|
|
jmp plot_star
|
|
|
|
new_star:
|
|
ldy XX
|
|
jsr random_star
|
|
|
|
jmp plot_star_continue
|
|
|
|
plot_star:
|
|
;================================
|
|
; plot routine
|
|
;================================
|
|
; put address in GBASL/GBASH
|
|
; Xcoord in XPOS
|
|
; Ycoord in Y
|
|
|
|
|
|
tya
|
|
and #$fe
|
|
tay
|
|
|
|
lda gr_offsets,Y ; lookup low-res memory address ; 4
|
|
clc ; 2
|
|
adc XPOS ; 3
|
|
sta GBASL ; 3
|
|
iny ; 2
|
|
|
|
lda gr_offsets,Y ; 4
|
|
adc DRAW_PAGE ; add in draw page offset ; 3
|
|
sta GBASH ; 3
|
|
;===========
|
|
;
|
|
ldy #0
|
|
lda YPOS
|
|
and #$1
|
|
bne plot_odd
|
|
plot_even:
|
|
lda COLOR
|
|
and #$0f
|
|
sta COLOR
|
|
lda (GBASL),Y
|
|
and #$f0
|
|
jmp plot_write
|
|
plot_odd:
|
|
lda COLOR
|
|
and #$f0
|
|
sta COLOR
|
|
lda (GBASL),Y
|
|
and #$0f
|
|
plot_write:
|
|
ora COLOR
|
|
sta (GBASL),Y
|
|
|
|
plot_star_continue:
|
|
|
|
|
|
;==============================
|
|
ldx XX
|
|
|
|
dex
|
|
bmi move_stars
|
|
; bpl draw_stars
|
|
jmp draw_stars
|
|
|
|
|
|
;=============================
|
|
; Move stars
|
|
move_stars:
|
|
ldy #(NUMSTARS-1)
|
|
move_stars_loop:
|
|
|
|
clc
|
|
lda star_z,Y
|
|
adc #1
|
|
sta star_z,Y
|
|
and #64
|
|
beq move_loop_skip
|
|
|
|
jsr random_star
|
|
|
|
move_loop_skip:
|
|
dey
|
|
bpl move_stars_loop
|
|
|
|
|
|
|
|
starfield_keyboard:
|
|
|
|
jsr get_key ; get keypress ; 6
|
|
|
|
lda LASTKEY ; 3
|
|
|
|
cmp #('Q') ; if quit, then return
|
|
bne skipskip
|
|
rts
|
|
|
|
skipskip:
|
|
|
|
;==================
|
|
; flip pages
|
|
;==================
|
|
|
|
jsr page_flip ; 6
|
|
|
|
;==================
|
|
; loop forever
|
|
;==================
|
|
|
|
jmp starfield_loop ; 3
|
|
|
|
|
|
; matches scroll_row1 - row3
|
|
star_x EQU $8A00
|
|
star_y EQU $8B00
|
|
star_z EQU $8C00
|
|
|
|
;===================
|
|
; star number in Y
|
|
; FIXME: increment at end?
|
|
; X trashed
|
|
random_star:
|
|
; random x location
|
|
ldx RANDOM_POINTER
|
|
lda random_table,X
|
|
inc RANDOM_POINTER
|
|
sta star_x,Y
|
|
|
|
; random y location
|
|
ldx RANDOM_POINTER
|
|
lda random_table,X
|
|
inc RANDOM_POINTER
|
|
sta star_y,Y
|
|
|
|
; random z location
|
|
ldx RANDOM_POINTER
|
|
lda random_table,X
|
|
inc RANDOM_POINTER
|
|
and #$3f
|
|
sta star_z,Y
|
|
|
|
rts
|
|
|
|
;===============================================
|
|
; External modules
|
|
;===============================================
|
|
|
|
;.include "../asm_routines/hlin_clearscreen.s"
|
|
.include "../asm_routines/pageflip.s"
|
|
.include "../asm_routines/gr_setpage.s"
|
|
.include "../asm_routines/keypress.s"
|
|
.include "../asm_routines/gr_putsprite.s"
|
|
.include "../asm_routines/text_print.s"
|
|
.include "../asm_routines/gr_offsets.s"
|
|
.include "../asm_routines/gr_fast_clear.s"
|
|
|
|
;===============================================
|
|
; Variables
|
|
;===============================================
|
|
|
|
|
|
.include "../asm_routines/multiply_fast.s"
|
|
|
|
|
|
;======================
|
|
; some "random" numbers
|
|
;======================
|
|
random_table:
|
|
.byte 103,198,105,115, 81,255, 74,236, 41,205,186,171,242,251,227, 70
|
|
.byte 124,194, 84,248, 27,232,231,141,118, 90, 46 ,99, 51,159,201,154
|
|
.byte 102, 50, 13,183, 49, 88,163, 90, 37, 93, 5, 23, 88,233, 94,212
|
|
.byte 171,178,205,198,155,180, 84, 17, 14,130,116, 65, 33, 61,220,135
|
|
.byte 112,233, 62,161, 65,225,252,103, 62, 1,126,151,234,220,107,150
|
|
.byte 143, 56, 92, 42,236,176, 59,251, 50,175, 60, 84,236, 24,219, 92
|
|
.byte 2, 26,254, 67,251,250,170, 58,251, 41,209,230, 5, 60,124,148
|
|
.byte 117,216,190, 97,137,249, 92,187,168,153, 15,149,177,235,241,179
|
|
.byte 5,239,247, 0,233,161, 58,229,202, 11,203,208, 72, 71,100,189
|
|
.byte 31, 35, 30,168, 28,123,100,197, 20,115, 90,197, 94, 75,121, 99
|
|
.byte 59,112,100, 36, 17,158, 9,220,170,212,172,242, 27, 16,175, 59
|
|
.byte 51,205,227, 80, 72, 71, 21, 92,187,111, 34, 25,186,155,125,245
|
|
.byte 11,225, 26, 28,127, 35,248, 41,248,164, 27, 19,181,202, 78,232
|
|
.byte 152, 50, 56,224,121, 77, 61, 52,188, 95, 78,119,250,203,108, 5
|
|
.byte 172,134, 33, 43,170, 26, 85,162,190,112,181,115, 59, 4, 92,211
|
|
.byte 54,148,179,175,226,240,228,158, 79, 50, 21, 73,253,130, 78,169
|
|
|
|
z_table:
|
|
; 1/16.0 - 1/12.25
|
|
.byte $10,$10,$10,$10,$11,$11,$11,$11,$12,$12,$12,$13,$13,$14,$14,$14
|
|
; 1/12.0 - 1/8.25
|
|
.byte $15,$15,$16,$16,$17,$17,$18,$18,$19,$1A,$1A,$1B,$1C,$1D,$1E,$1F
|
|
; 1/8.0 - 1/4.25
|
|
.byte $20,$21,$22,$23,$24,$25,$27,$28,$2A,$2C,$2E,$30,$33,$35,$38,$3C
|
|
; 1/4.0 - 1/0.25
|
|
.byte $40,$44,$49,$4E,$55,$5D,$66,$71,$80,$92,$AA,$CC,$00,$55,$00,$00
|
|
|