dos33fsprogs/mode7/starfield_demo.s
2017-12-31 17:29:21 -05:00

361 lines
7.3 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
; always multiply with low byte as zero
sta NUM2L ; 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) ; 2
draw_stars:
stx XX ; 3
;================
; calculate color
;================
lda #$ff ; want if z<16, color = 5 ; 2
sta COLOR ; if 16<z<32 color = 13 ; 3
; if 32<z<64 color = 15
lda star_z,X ; 4
tay ; put star_z[i] in X for later ; 2
cmp #32 ; 2
bpl done_color ; 2nt/3
cmp #16 ; 15 -1 16 0 17 1 ; 2
bpl second_color ; 2nt/3
lda #$55 ; 2
sta COLOR ; 3
jmp done_color ; 3
second_color:
lda #$dd ; 2
sta COLOR ; 3
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 ; 4
sta NUM1L ; F ; 3
; adjust spacez for 58+
; all this logic to avoid having a 128 byte table of mostly zero
lda #0 ; I ; 2
clc ; 2
cpy #60 ; 59 -1 60 0 61 1 ; 2
bmi no_adjust ; 2nt/3
adc #1 ; 60, 61 = 1 ; 2
cpy #62 ; 61 -1 62 0 63 1 ; 2
bmi no_adjust ; 2nt/3
adc #1 ; 62 = 2 ; 2
cpy #63 ; 62 = -1 63 = 0 64 = not possible ; 2
bne no_adjust ; 2nt/3
adc #2 ; 63 = 4 ; 2
no_adjust:
sta NUM1H ; store int part of spacez ; 3
; load stars[i].x into NUM2H:NUM2L
; NUM2L is always zero
ldy XX ; 3
lda star_x,Y ; 4
sta NUM2H ; 3
sec ; don't reuse old values ; 2
jsr multiply ; 6+?
; integer result in X
txa ; 2
clc ; 2
adc #20 ; center on screen ; 2
sta XPOS ; save for later ; 3
; calculate y value, stars[i].y/stars[i].z
; 1/stars[i].z is still in NUM1H:NUM1L
ldy XX ; reload index ; 3
lda star_y,Y ; load integer part of star_ ; 4
sta NUM2H ; 3
clc ; reuse old values ; 2
jsr multiply ; 6+
; integer result in X
txa ; 2
clc ; 2
adc #20 ; center the value ; 2
tay ; Y is YPOS ; 2
sty YPOS ; put Y value in Y to plot ; 3
;============================
; Check Limits
;============================
; ldy YPOS
bmi new_star ; 2nt/3
cpy #40 ; 2
bpl new_star ; if < 0 or > 40 then done ; 2nt/3
lda XPOS ; 3
bmi new_star ; 2nt/3
cmp #40 ; 2
bpl new_star ; if < 0 or > 40 then done ; 2nt/3
; FIXME: sort out all of these jumps to be more efficient
bmi plot_star ; 2
new_star:
ldy XX ; 3
jsr random_star ; 6
jmp plot_star_continue ; 3
plot_star:
;================================
; plot routine
;================================
; put address in GBASL/GBASH
; Xcoord in XPOS
; Ycoord in Y
tya ; 2
and #$fe ; mask to make it even ; 2
tay ; 2
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/pageflip.s"
.include "../asm_routines/gr_setpage.s"
;.include "../asm_routines/keypress.s"
;.include "../asm_routines/gr_putsprite.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