Homing Attack - Variant 2 - Quadratic Method

In this method, the Sonic goes in enemy direction by the edges of a imaginary rectangle between they.



When the Sonic enter in blue range, the horizontal alignment is activated and the vertical alignment is disabled.

To download the Rom and the Source Code, click here: http://goo.gl/2SH7T
To apply this you need first apply the Homing Attack in Sonic 1 guide.


Now in HA_Move change this:

Code:

; Recalculating the distance between the Sonic and the object (d1 = x distance / d2 = y distance)
      move.w  8(a1),d1   ; move the object x-position to d1
      move.w  $C(a1),d2   ; move the object y-position to d2
      sub.w  8(a0),d1   ; sub sonic x-position of object x-position
      sub.w  $C(a0),d2   ; sub sonic y-position of object y-position

      jsr      (CalcAngle).l   ; calculates the angle
      jsr      (CalcSine).l   ; calculates the sine and the cosine
      muls.w  #$C,d1         ; multiply cosine by $C
      move.w  d1,$10(a0)      ; move d1 to X-velocity
      muls.w  #$C,d0         ; multiply sine by $C
      move.w  d0,$12(a0)      ; move d0 to Y-velocity

Sonic_HA_rts:
      rts                  ; return

To this:

Code:

   ; vertical alignment
      move.w  $C(a1),d2   ; move the object y-position to d2
      sub.w  $C(a0),d2   ; sub sonic y-position of object y-position
      move.w   d2,d3      ; copy y-distance to d3
      muls.w   d3,d3      ; vertical distance squared
      cmp.w   #400,d3      ; is y-distance of Sonic, less than or equal 20 pixels of the object? (20^2=400 // $14^2=$190)
      ble.s   Ha_GO      ; if yes, attack him
      clr.w  $10(a0)      ; if not, stop Sonic's X-velocity
      muls.w   #5,d2         ; multiply y-distance by 5
      add.w  d2,$12(a0)      ; add y-distance*5 to Y-velocity
      rts


Ha_GO:   ; horizontal alignment
      move.w  8(a1),d1   ; move the object x-position to d1
      sub.w  8(a0),d1   ; sub sonic x-position of object x-position
      clr.w  $12(a0)      ; stop Sonic's Y-velocity
      muls.w   #5,d1         ; multiply x-distance by 5
      add.w  d1,$10(a0)      ; add x-distance*5 to X-velocity

Sonic_HA_rts:
      rts                  ; return

Cool!!!

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