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Here a Method that not need the CalcAngle and CalcSine, the main difference is the "speed by distance" (near = slow, far = fast). Because how much closer of the object (short distances is a low value), lower is the speed (lower speeds is a low value).
To see this already compiled, download here: http://goo.gl/Pd0fN
To apply this, you need first apply the Homing Attack in Sonic 1 guide.
After apply the guide, follows below.
First in HA_Move delete this:
Again in HA_Move change this:
Now because the "speed by distance", we need more time to hit the enemy; in HA_calcdistance2 change this:
After applying these changes, your code must be equal to this below:
To see this already compiled, download here: http://goo.gl/Pd0fN
To apply this, you need first apply the Homing Attack in Sonic 1 guide.
After apply the guide, follows below.
First in HA_Move delete this:
- Code:
jsr (CalcAngle).l ; calculates the angle
jsr (CalcSine).l ; calculates the sine and the cosine
Again in HA_Move change this:
- Code:
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
- Code:
muls.w #$10,d1 ; multiply x-distance by $10
move.w d1,$10(a0) ; move d1 to X-velocity
muls.w #$10,d2 ; multiply y-distance by $10
move.w d2,$12(a0) ; move d2 to Y-velocity
Now because the "speed by distance", we need more time to hit the enemy; in HA_calcdistance2 change this:
- Code:
move.b #30,($FFFFFFD1).w ; number of frames Sonic can chasing the object
- Code:
move.b #120,($FFFFFFD1).w ; number of frames Sonic can chasing the object
After applying these changes, your code must be equal to this below:
- Code:
; ---------------------------------------------------------------------------
; Subroutine Sonic_Homingattack
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
Sonic_Homingattack:
tst.b ($FFFFFFD1).w ; is Sonic chasing some object?
bne.w HA_Move ; if yes, chase him
move.b ($FFFFF603).w,d1 ; read controller
andi.b #$40,d1 ; is A pressed?
beq.w Sonic_HA_rts ; if not, branch
lea ($FFFFD800).w,a1 ; start at the first level object RAM
; ---------------------------------------------------------------------------
HA_enemylist:
tst.b (a1) ; is a Null object
beq.s HA_nextobject ; if yes, branch
cmpi.b #5,$20(a1) ; is not an enemy object? (spring, explosion, platform, collected ring, flame thrower (SBZ), among others)
bcs.w HA_nextobject ; if yes, branch
; cmpi.b #5,$20(a1) ; is Burrobot enemy (LZ)
; beq.w HA_calcdistance ; if yes, branch
; cmpi.b #6,$20(a1) ; is Crabmeat enemy (GHZ, SYZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #8,$20(a1) ; is Buzz Bomber enemy (GHZ, MZ, SYZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #9,$20(a1) ; is Chopper enemy (GHZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$A,$20(a1) ; is Jaws enemy (LZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$B,$20(a1) ; is Caterkiller enemy (MZ, SBZ) / Orbinaut enemy (LZ, SLZ, SBZ) / Basaran enemy (MZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$C,$20(a1) ; is Roller enemy (SYZ) / Newtron enemy (GHZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$D,$20(a1) ; is Newtron enemy (GHZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$E,$20(a1) ; is Roller enemy (SYZ)
; beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$F,$20(a1) ; is Eggman
; beq.s HA_calcdistance ; if yes, branch
cmpi.b #$F,$20(a1) ; is some enemy of the list above?
bls.s HA_calcdistance ; if yes, branch
cmpi.b #$46,$20(a1) ; is the monitor?
beq.s HA_calcdistance ; if yes, branch
; cmpi.b #$47,$20(a1) ; is the ring?
; beq.s HA_calcdistance ; if yes, branch
cmpi.b #$52,$20(a1) ; is giant ring for entry to special stage?
beq.s HA_calcdistance ; if yes, branch
cmpi.b #$CC,$20(a1) ; is Yadrin enemy (SYZ)
beq.s HA_calcdistance ; if yes, branch
HA_nextobject:
adda.w #$40,a1 ; jump to next object RAM entry
cmpa.w #$F000,a1 ; already tested all object RAM entry?
blt.s HA_enemylist ; if not, return to enemy list
rts
; ---------------------------------------------------------------------------
HA_calcdistance: ; distance calculator
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
; ---------------------------------------------------------------------------
; test if the Sonic is facing the object
btst #0,$22(a0) ; is sonic facing left?
beq.s HA_faceleft ; if yes, branch
cmpi.w #8,d1 ; is distance of Sonic, less than 8 pixels of the object?
blt.s HA_calcdistance2 ; if yes, branch
bra.s HA_nextobject
HA_faceleft:
cmpi.w #-8,d1 ; is distance of Sonic, greater than -8 pixels of the object?
bgt.s HA_calcdistance2 ; if yes, branch
bra.s HA_nextobject
; end of test
; ---------------------------------------------------------------------------
HA_calcdistance2: ; continuation of distance calculator
muls.w d1,d1 ; horizontal distance squared
muls.w d2,d2 ; vertical distance squared
add.l d2,d1 ; add vertical distance to horizontal distance
cmp.l #16384,d1 ; is distance of Sonic, greater than or equal 128 pixels of the object? (128^2=16384 // $80^2=$4000)
bge.s HA_nextobject ; if yes, don't execute the homing attack
move.w #$BC,d0 ; set homing attack sound
jsr (PlaySound).l ; play homing attack sound
bclr #4,$22(a0) ; clear "uncontrolled jump" flag
move.b #120,($FFFFFFD1).w ; number of frames Sonic can chasing the object
move.l a1,($FFFFFFD2).w ; save the object address that Sonic is chasing
; ---------------------------------------------------------------------------
HA_Move:
movea.l ($FFFFFFD2).w,a1 ; load the object address that Sonic is chasing
subi.b #1,($FFFFFFD1).w ; sub 1 of frames counter
tst.b ($FFFFFFD1).w ; the time to the Sonic chasing some object is over?
beq.w Sonic_HA_rts ; if yes, don't make the Homing Attack
; ---------------------------------------------------------------------------
; 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
muls.w #$10,d1 ; multiply x-distance by $10
move.w d1,$10(a0) ; move d1 to X-velocity
muls.w #$10,d2 ; multiply y-distance by $10
move.w d2,$12(a0) ; move d2 to Y-velocity
Sonic_HA_rts:
rts ; return
; Command of Homingattack end here
