ASM to Sega Genesis Platform

All about assembly programming in the Sega Genesis console.

    New CalcSine



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    Data de inscrição : 2011-01-09
    Current Project : Sonic Open Source Project

    New CalcSine

    Post  OuricoDoido on Sat Jan 29, 2011 2:32 pm

    I made a CalcSine that does not use table:

    ; ---------------------------------------------------------------------------
    ; 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)

          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

          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

          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

          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
    ; End of function CalcSine

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    Re: New CalcSine

    Post  hacker___ on Tue Oct 29, 2013 8:56 pm

    I'm not going to use this because you stol it from other gam (not hax)(
    Green Snake

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    Re: New CalcSine

    Post  Green Snake on Fri Dec 13, 2013 4:56 am

    Eww you idiot, wasting processor time >:(

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    Re: New CalcSine

    Post  JoshDP on Mon Jun 29, 2015 3:05 pm

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

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    Re: New CalcSine

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