New CalcSine

Code:

; ---------------------------------------------------------------------------
; Subroutine to calculate sine and cosine of an angle
; d0 = input byte = angle (360 degrees == 256)
; d0 = output word = 255 * sine(angle)
; d1 = output word = 255 * cosine(angle)
; ---------------------------------------------------------------------------
; New CalcSine without table, the max diference of original CalcSine
; is + or - 4 in sine or cosine value.
; ---------------------------------------------------------------------------


; ||||||||||||||| S U B   R O U T   I N E |||||||||||||||||||||||||||||||||||||||


CalcSine:            ; XREF: SS_BGAnimate; et al
      movem.l   d2-d5,-(sp)      ; save the variables that will be changed in this calculation
      andi.w   #$FF,d0         ; adapt a angle (alpha > 255) to a angle (alpha < 256)
      move.w   d0,d5         ; copy the angle, because after loop we need again the angle (to sine)
      moveq   #1,d4         ; repeat the loop 1 time (to sine)

CalcSine_loop_start:
      moveq   #0,d3         ; reset the "negate the sine or cosine in end" flag
      move.w   d5,d0         ; get the angle value (to sine after loop)

      cmpi.w   #128,d0               ; is the angle in 1st or 2nd quadrant?
      blt.s   CalcSine_cos_to_sine   ; if yes, don't rotate the angle to fix it in 1st or 2nd quadrant
      subi.b   #128,d0               ; rotate the angle 128º (180º in real world)
      add.b   #1,d3               ; set to negate the sine or cosine in end of calculation

CalcSine_cos_to_sine:
      tst.b   d4                  ; sine or cosine is being calculated?
      beq.s   CalcSine_bhaskara      ; if is the sine, branch
      cmpi.w   #64,d0               ; is the angle in 1st quadrant?
      blt.s   CalcSine_cos_to_sine2   ; if yes, rotate it 64º
      subi.b   #64,d0               ; if not, rotate it -64º (-90º in real world)
      add.b   #1,d3               ;  add 1 in "negate the sine or cosine in end" flag (if the d3=2, don't negate the result in end)
      bra.s   CalcSine_bhaskara      ; calculate the cosine

CalcSine_cos_to_sine2:
      addi.b   #64,d0               ; rotate the angle 64º (90º in real world)

CalcSine_bhaskara:         ; Sine = 12*Beta/Delta
                     ; Beta = (128-angle)*angle
                     ; Delta = (28800-Beta)/128

      move.l   #128,d1   ; Beta /// 128
      sub.w   d0,d1   ; Beta /// 128-angle
      muls.w   d0,d1   ; Beta /// (128-angle)*angle
      move.l   #28800,d2   ; Delta /// 28800
      sub.w   d1,d2      ; Delta /// 28800-Beta
      divs.w   #128,d2      ; Delta /// (28800-Beta)/128
      muls.w   #12,d1   ; SINE /// 12*Beta
      divs.w   d2,d1   ; SINE /// 12*Beta/Delta

      cmpi.b   #1,d3         ; is d3=1? negate the result?
      bne.s   CalcSine_save   ; if not, don't negate the result
      neg   d1               ; if d3=1, negate the result

CalcSine_save:
      movem.l   d1,-(sp)            ; save the result in sp
      dbf.w   d4,CalcSine_loop_start   ; if the sine don't was calculated, return and calculate it

      movem.l   (sp)+,d0-d5      ; load the results (sine to d0 and cosine to d1) and the variables that were modified
      rts
; End of function CalcSine

Green Snake wrote:yum you idiot, washing processor time >:(

JoshDP wrote:

Green Snake wrote:you idiot, I liek 2 waste processor time >

me too =E

OuricoDoido wrote:I aM gAy


(Last edited by Jdpense on Wednesday September 16, 2020 10:06 pm; edited 1 time in total)

Jdpense wrote:

OuricoDoido wrote:I aM gAy


(Last edited by Jdpense on Wednesday September 16, 2020 10:06 pm; edited 1 time in total)

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