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Sine and Cosine

This commit is contained in:
yenatch 2013-09-02 00:12:27 -04:00
parent 5b38b377f2
commit 9f7c4ef0b4
1 changed files with 41 additions and 22 deletions
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63
main.asm
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@ -1307,24 +1307,29 @@ GetSpriteDirection: ; 1b07
; 1b0f ; 1b0f
Function1b0f: ; 1b0f Cosine: ; 1b0f
add $10 ; Return d * cos(a) in hl
add $10 ; 90 degrees
Sine: ; 1b11
; Return d * sin(a) in hl
; a is a signed 6-bit value.
Function1b11: ; 1b11
ld e, a ld e, a
ld a, [hROMBank] ld a, [hROMBank]
push af push af
ld a, BANK(Function84d9) ld a, BANK(_Sine)
rst Bankswitch rst Bankswitch
call Function84d9 call _Sine
pop af pop af
rst Bankswitch rst Bankswitch
ret ret
; 1b1e ; 1b1e
Function1b1e: ; 1b1e Function1b1e: ; 1b1e
ld [$d003], a ld [$d003], a
xor a xor a
@ -11138,7 +11143,7 @@ Function4c5d: ; 4c5d
inc [hl] inc [hl]
ld a, [hl] ld a, [hl]
ld d, $60 ld d, $60
call Function1b11 call Sine
ld a, h ld a, h
sub $60 sub $60
ld hl, $001a ld hl, $001a
@ -11211,7 +11216,7 @@ Function4cc9: ; 4cc9
inc [hl] inc [hl]
ld a, [hl] ld a, [hl]
ld d, $60 ld d, $60
call Function1b11 call Sine
ld a, h ld a, h
sub $60 sub $60
ld hl, $001a ld hl, $001a
@ -11302,7 +11307,7 @@ Function4d4f: ; 4d4f
inc [hl] inc [hl]
ld a, [hl] ld a, [hl]
ld d, $60 ld d, $60
call Function1b11 call Sine
ld a, h ld a, h
sub $60 sub $60
ld hl, $001a ld hl, $001a
@ -17031,17 +17036,22 @@ Function849d: ; 849d
ret ret
; 84d9 ; 84d9
Function84d9: ; 84d9 _Sine: ; 84d9
; A simple sine function.
; Return d * sin(e) in hl.
; e is a signed 6-bit value.
ld a, e ld a, e
and $3f and %111111
cp $20 cp %100000
jr nc, .asm_84e5 jr nc, .negative
call Function84ef call Function84ef
ld a, h ld a, h
ret ret
.asm_84e5 .negative
and $1f and %011111
call Function84ef call Function84ef
ld a, h ld a, h
xor $ff xor $ff
@ -17053,27 +17063,36 @@ Function84ef: ; 84ef
ld e, a ld e, a
ld a, d ld a, d
ld d, 0 ld d, 0
ld hl, $450b ld hl, SineWave
add hl, de add hl, de
add hl, de add hl, de
ld e, [hl] ld e, [hl]
inc hl inc hl
ld d, [hl] ld d, [hl]
ld hl, 0 ld hl, 0
.asm_84fe
srl a
jr nc, .asm_8503
add hl, de
.asm_8503 ; Factor amplitude
.multiply
srl a
jr nc, .even
add hl, de
.even
sla e sla e
rl d rl d
and a and a
jr nz, .asm_84fe jr nz, .multiply
ret ret
; 850b ; 850b
INCBIN "baserom.gbc", $850b, $854b - $850b SineWave: ; 850b
; A $20-word table representing a sine wave.
; 90 degrees is index $10 at a base amplitude of $100.
x set 0
rept $20
dw (sin(x) + (sin(x) & $ff)) >> 8 ; round up
x set x + $100 * $40000
endr
; 854b
GetPredefFn: ; 854b GetPredefFn: ; 854b