ref: 9973e43d5aaffeef9d68994a665d2b0231f56f41
dir: /engine/sine.asm/
_Sine:: ; 84d9 ; A simple sine function. ; Return d * sin(e) in hl. ; e is a signed 6-bit value. ld a, e and %111111 cp %100000 jr nc, .negative call .ApplySineWave ld a, h ret .negative and %011111 call .ApplySineWave ld a, h xor -1 inc a ret .ApplySineWave: ; 84ef ld e, a ld a, d ld d, 0 ld hl, .sinewave add hl, de add hl, de ld e, [hl] inc hl ld d, [hl] ld hl, 0 ; Factor amplitude .multiply srl a jr nc, .even add hl, de .even sla e rl d and a jr nz, .multiply ret .sinewave ; 850b ; A $20-word table representing a sine wave. ; 90 degrees is index $10 at a base amplitude of $100. sine_wave $100