diff options
| -rw-r--r-- | main.asm | 61 |
1 files changed, 40 insertions, 21 deletions
@@ -1307,24 +1307,29 @@ GetSpriteDirection: ; 1b07 ; 1b0f -Function1b0f: ; 1b0f - add $10 +Cosine: ; 1b0f +; Return d * cos(a) in hl + add $10 ; 90 degrees + +Sine: ; 1b11 +; Return d * sin(a) in hl +; a is a signed 6-bit value. -Function1b11: ; 1b11 ld e, a ld a, [hROMBank] push af - ld a, BANK(Function84d9) + ld a, BANK(_Sine) rst Bankswitch - call Function84d9 + call _Sine pop af rst Bankswitch ret ; 1b1e + Function1b1e: ; 1b1e ld [$d003], a xor a @@ -11138,7 +11143,7 @@ Function4c5d: ; 4c5d inc [hl] ld a, [hl] ld d, $60 - call Function1b11 + call Sine ld a, h sub $60 ld hl, $001a @@ -11211,7 +11216,7 @@ Function4cc9: ; 4cc9 inc [hl] ld a, [hl] ld d, $60 - call Function1b11 + call Sine ld a, h sub $60 ld hl, $001a @@ -11302,7 +11307,7 @@ Function4d4f: ; 4d4f inc [hl] ld a, [hl] ld d, $60 - call Function1b11 + call Sine ld a, h sub $60 ld hl, $001a @@ -17031,17 +17036,22 @@ Function849d: ; 849d ret ; 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 - and $3f - cp $20 - jr nc, .asm_84e5 + and %111111 + cp %100000 + jr nc, .negative + call Function84ef ld a, h ret -.asm_84e5 - and $1f +.negative + and %011111 call Function84ef ld a, h xor $ff @@ -17053,27 +17063,36 @@ Function84ef: ; 84ef ld e, a ld a, d ld d, 0 - ld hl, $450b + ld hl, SineWave add hl, de add hl, de ld e, [hl] inc hl ld d, [hl] ld hl, 0 -.asm_84fe + +; Factor amplitude +.multiply srl a - jr nc, .asm_8503 + jr nc, .even add hl, de - -.asm_8503 +.even sla e rl d and a - jr nz, .asm_84fe + jr nz, .multiply ret ; 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 |