[S1] How to add extra characters

As we don't have a working multi-character guide anywhere (Trust me, this one doesn't work), so I thought I'd make a full guide on this. the good part about this guide is that: 1: It uses techniques to load the art/mappings/DPLC as fast as possible, leaving more time for whatever else code the game is running; 2: You have multiple options on how to do things, so you can select the most fitting way; 3: You can have up to 64 characters using this guide, so you should not run out of them in a while. The character IDs are always in increments of 4, to save some processor cycles; 4: It is easy to add more characters, you have to do barely anything! Just note that this is based on the HiveBrain 2005 disassembly, and you may need to do some extra work for SVN/HG/Git disassemblies. Also note that this will NOT work on Sonic 2 or Sonic 3! I am also going to use Tails as an example, so replace each reference to Tails with your characters name!

Step 1: Preparations.

Spoiler

File includes

That said, lets begin! So, the first thing you want to do, is get the proper art, mappings, DPLC, Animation, and palette files for your new character. If you miss one of these, this tutorial wont work. The files should be located at same places where normal Sonic's files of same type are at. As an example, you would put the new character DPLC file at the _inc folder (in case of HiveBrain 2005). As we are on the subject of the files, lets include them to the ROM:

First, go to label "Art_Sonic", and you'll see something like this:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Uncompressed graphics - Sonic
3. ; ---------------------------------------------------------------------------
4. Art_Sonic:  incbin  artunc\sonic.bin    ; Sonic
5.         even

What you want to do this, is copy this, and replace each Sonic with Tails. Also make sure You use the correct file name (If Tails.bin does not exist, make sure to change either the incbin reference or the original file name to match). So, in my case, this is what I would have:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Uncompressed graphics - Tails
3. ; ---------------------------------------------------------------------------
4. Art_Tails:  incbin  artunc\tails.bin    ; Tails' art
5.         even

Note that this should be located either before or after the Sonic's sequence, as so:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Uncompressed graphics - Sonic
3. ; ---------------------------------------------------------------------------
4. Art_Sonic:  incbin  artunc\sonic.bin    ; Sonic
5.         even
6. ; ---------------------------------------------------------------------------
7. ; Uncompressed graphics - Tails
8. ; ---------------------------------------------------------------------------
9. Art_Tails:  incbin  artunc\tails.bin    ; Tails' art
10.         even

Ok, next up mappings and DPLC. Go to "Map_Sonic", and you'll see something along the lines of this:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Sprite mappings - Sonic
3. ; ---------------------------------------------------------------------------
4. Map_Sonic:
5.     include "_maps\Sonic.asm"
6. ; ---------------------------------------------------------------------------
7. ; Uncompressed graphics loading array for Sonic
8. ; ---------------------------------------------------------------------------
9. SonicDynPLC:
10.     include "_inc\Sonic dynamic pattern load cues.asm"

Do something similar to it too, than with the art. So, this is what I'd have:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Sprite mappings - Sonic
3. ; ---------------------------------------------------------------------------
4. Map_Sonic:
5.     include "_maps\Sonic.asm"
6. ; ---------------------------------------------------------------------------
7. ; Uncompressed graphics loading array for Sonic
8. ; ---------------------------------------------------------------------------
9. SonicDynPLC:
10.     include "_inc\Sonic dynamic pattern load cues.asm"
11. ; ---------------------------------------------------------------------------
12. ; Sprite mappings - Tails
13. ; ---------------------------------------------------------------------------
14. Map_Tails:
15.     include "_maps\Tails.asm"
16. ; ---------------------------------------------------------------------------
17. ; Uncompressed graphics loading array for Tails
18. ; ---------------------------------------------------------------------------
19. TailsDynPLC:
20.     include "_inc\Tails dynamic pattern load cues.asm"

Next, let's do the animations file. Go to "SonicAniData", and you'll see this:

Code (ASM):

1. SonicAniData:
2.     include "_anim\Sonic.asm"

In my case, I would change it to:

Code (ASM):

1. SonicAniData:
2.     include "_anim\Sonic.asm"
3. TailsAniData:
4.     include "_anim\Tails.asm"

All we need to include now is the palette. Go to "Pal_Sonic", and you'll see something like this:

Code (ASM):

1. Pal_Sonic:      incbin  pallet\sonic.bin
2. ...
3. Pal_LZSonWater: incbin  pallet\son_lzuw.bin ; Sonic (underwater in LZ) pallet
4. Pal_SBZ3SonWat: incbin  pallet\son_sbzu.bin ; Sonic (underwater in SBZ act 3) pallet

Still, do the same thing than with the art. I'd do this:

Code (ASM):

1. Pal_Sonic:  incbin  pallet\sonic.bin    ; Sonic's normal palette
2. Pal_Tails:  incbin  pallet\Tails.bin    ; Tails' normal palette
3. ...
4. Pal_LZSonWater: incbin  pallet\son_lzuw.bin ; Sonic (underwater in LZ) palette
5. Pal_SBZ3SonWat: incbin  pallet\son_sbzu.bin ; Sonic (underwater in SBZ act 3) palette
6. Pal_TailsLZ:    incbin  pallet\tails_lz.bin ; Tails (underwater in LZ) palette
7. Pal_TailsSBZ3:  incbin  pallet\tails_sbz3.bin   ; Tails (underwater in SBZ act 3) palette

Sonic 2's DPLC

if you have followed either Add Spin Dash to Sonic 1 (Part 3), or How to optimize Shield Art loading in Sonic 1 (Step 1), you have already it on your hack. If not, however, you must add it. I suggest following the latter link.

Different versions

Good! Now we should have everything we need for your new character to work! Well, except all the code behind it of course. But before we start on it, build your ROM, and make sure it wont complain about any "undefined errors" or "this and that not found". If some of them comes up, fix them up first. If not, lets continue. Now. you should decide which version you want to use, and find free RAM space.

Version 1: Everything is stored via RAM. Requires 32 bytes of free RAM. Fastest.
Version 2: Animation offsets are referenced via tables. Requires 8 bytes of free RAM. Slower.
version 3: Everything is referenced via tables. Requires 0 bytes of free RAM. Slowest.

So, after you have decided the technique you want to use, you want to go to beginning of your ROM, and just before

Code (ASM):

1. align macro
2.     cnop 0,\1
3.     endm

You want to add this equate:

Code (ASM):

1. Current_Character   equ     ; whatever the character you are using is

Now, you must find 1 free byte of RAM. I suggest you to use "$FFFFFFF9", as it is 1-byte free address. In any case, put the address after the "equ" (You need at least 1 space between them). If you want to know more about unused addresses, go here. What this flag is used for, is to store what character you are using. Note that referencing "Current_Character" and not the RAM address you chose is much better, as you can easily mass-change the RAM itself, and it is easier to identify what it is used for.

You also need some other RAM equates, but they depend on the version you use. Here is what you need for version 1:

Spoiler

Code (ASM):

1. Player_ArtLoc       equ     ; 4 bytes ; pointer for players art location (can also be used for special art if needed to ;) )
2. Player_DPLCLoc      equ     ; 4 bytes ; pointer for players DPLC location (can be used for special DPLCs)
3. Player_AniDat       equ     ; 4 bytes ; pointer for players animation data location (can be used for special animations)
4. PAni_Run        equ     ; 4 bytes ; pointer for players Run  animation (can be used for special animation)
5. PAni_Walk       equ     ; 4 bytes ; pointer for players Walk animation (can be used for special animation)
6. PAni_Roll       equ     ; 4 bytes ; pointer for players Roll animation (can be used for special animation)
7. PAni_Roll2      equ     ; 4 bytes ; pointer for players Roll animation (can be used for special animation)
8. PAni_Push       equ     ; 4 bytes ; pointer for players Push animation (can be used for special animation)

Version 2:

Spoiler

Code (ASM):

1. Player_ArtLoc       equ     ; 4 bytes ; pointer for players art location (can also be used for special art if needed to ;) )
2. Player_DPLCLoc      equ     ; 4 bytes ; pointer for players DPLC location (can be used for special DPLCs)
3. Player_AniDat       equ     ; 4 bytes ; pointer for players animation data location (can be used for special animations)

Version 3: none.

Step 2: The actual code.

Spoiler

Palette

So, lets get to work! First of all, we want to do the simplest part, which will probably be palette. Head to "Level_LoadPal". You will see the following code:

Code (ASM):

1.         moveq   #3,d0
2.         bsr.w   PalLoad2    ; load Sonic's pallet line
3.         cmpi.b  #1,($FFFFFE10).w ; is level LZ?
4.         bne.s   Level_GetBgm    ; if not, branch
5.         moveq   #$F,d0      ; pallet number $0F (LZ)
6.         cmpi.b  #3,($FFFFFE11).w ; is act number 3?
7.         bne.s   Level_WaterPal  ; if not, branch
8.         moveq   #$10,d0     ; pallet number $10 (SBZ3)
9.  
10. Level_WaterPal:
11.         bsr.w   PalLoad3_Water  ; load underwater pallet (see d0)
12.         tst.b   ($FFFFFE30).w
13.         beq.s   Level_GetBgm
14.         move.b  ($FFFFFE53).w,($FFFFF64E).w

We don't want this. Replace with:

Code (ASM):

1.         lea $FFFFFB00,a2        ; normal palette
2.         lea $FFFFFA80,a3        ; underwater palette
3.         bsr LoadPlayerPalettes  ; load palette for current character
4.  
5.         cmpi.b  #1,$FFFFFE10.w      ; is level LZ?
6.         bne.s   Level_GetBgm        ; if not, branch
7.         tst.b   $FFFFFE30.w     ; has lamppost been hit?
8.         beq.s   Level_GetBgm        ; if not, branch
9.         move.b  $FFFFFE53.w,$FFFFF64E.w ; copy water direction to lamppost RAM

There are, however, few locations where Sonic's palette is loaded. It is optional to fix any of them, but for completions sake, here is how: In Title_ClrPallet, loc_3946, End_LoadData, and Cred_ClrPallet, replace following piece of code: (Note: Title screen uses it's own palette for Sonic, you need to find your own way to replace that.)

Code (ASM):

1.         moveq   #3,d0
2.         bsr.w   PalLoad1    ; load Sonic's pallet

With this:

Code (ASM):

1.         lea $FFFFFB80,a2        ; normal target palette
2.         lea $FFFFFA00,a3        ; underwater target palette
3.         bsr LoadPlayerPalettes  ; load palette for current character

Now we need the actual code to load the palette. Somewhere near "Pal_Sonic", insert this code:

Code (ASM):

1. ; ===========================================================================
2. ; ---------------------------------------------------------------------------
3. ; Subroutine to load correct player pallets
4. ; ---------------------------------------------------------------------------
5.  
6. LoadPlayerPalettes:
7.         moveq   #0,d1
8.         move.b  Current_Character.w,d1      ; get character ID
9.         move.l  CharPalList(pc,d1.w),a1     ; get normal palette to a1
10.  
11.         moveq   #7,d0               ; 16 palette entries
12.         bsr.s   Loc_Pal             ; load palettes to RAM
13.         cmpi.b  #1,$FFFFFE10.w          ; is LZ?
14.         bne.s   LPP_rts             ; if not, branch
15.  
16.         move.l  CharPalListLZ(pc,d1.w),a1   ; get underwater palette to a1
17.         cmpi.b  #3,$FFFFFE11.w          ; is act number 3?
18.         bne.s   LPP_UWPal           ; if not, branch
19.                 move.l  CharPalListSBZ3(pc,d1.w),a1 ; get SBZ3 underwater palette to a1
20.  
21. LPP_UWPal:
22.         moveq   #7,d0               ; 16 palette entries
23.         lea (a3),a2             ; put water palette to a2
24.         bsr.s   Loc_Pal             ; load to RAM
25.  
26. LPP_rts:
27.         rts                 ; return
28.  
29. ; ===========================================================================
30. ; ---------------------------------------------------------------------------
31. ; copy d0 + 1 longwords from a1 to a2
32. ; ---------------------------------------------------------------------------
33.  
34. loc_Pal:
35.         move.l  (a1)+,(a2)+     ; process next 2 palette entries
36.         dbf d0,loc_Pal      ; keep looping until d0 is 0
37.         rts             ; return

Next, we need to create the array of pointers for our desired player palettes. This isn't exactly complicated, so let me show example of how I would do it:

Code (ASM):

1. CharPalList:        dc.l Pal_Sonic, Pal_Tails
2. CharPalListLZ:      dc.l Pal_LZSonWater, Pal_TailsLZ
3. CharPalListSBZ3:    dc.l Pal_SBZ3SonWat, Pal_TailsSBZ3

It makes most sense to place this either under or above the LoadPlayerPalettes code I did show you above.

Art and dynamic pattern load cues

First off, go to LoadSonicDynPLC, and replace the entire routine with this:

version 1 and version 2:

Spoiler

Code (ASM):

1. LoadSonicDynPLC:
2.         movea.l Player_DPLCLoc,a2   ; get DPLC location
3.         move.w  #$F000,d4       ; offset in VRAM to store art
4.         move.l  Player_ArtLoc,d6    ; get art location
5.        
6.         moveq   #0,d0
7.         move.b  $1A(a0),d0  ; load frame number
8.         cmp.b   $FFFFF766.w,d0  ; check if equal with last queued frame
9.         beq.s   DPLC_End    ; if is, don't load new DPLC
10.         move.b  d0,$FFFFF766.w  ; remember queued frame
11. ; End of function LoadSonicDynPLC
12.  
13. ; ---------------------------------------------------------------------------
14. ; Subroutine to queue any pattern load cue
15. ; Input: a2 - DPLC file, d4 - VRAM address, d6 - Art file, d0 - frame number
16. ; ---------------------------------------------------------------------------
17.  
18. Load_DPLC:
19.         add.w   d0,d0       ; multiply by 2
20.         adda.w  (a2,d0.w),a2    ; get the right DPLC location
21.         moveq   #0,d5       ; quckly clear d5
22.         move.b  (a2)+,d5    ; then move the amount of requests to d5
23.         subq.w  #1,d5       ; subtract 1
24.         bmi.s   DPLC_End    ; if negative, branch away
25.  
26. DPLC_ReadEntry:
27.         moveq   #0,d1
28.         move.b  (a2)+,d1    ; get first byte to d1, and increment pointer
29.         lsl.w   #8,d1       ; shift 8 bits left
30.         move.b  (a2)+,d1    ; move second byte to d1
31.  
32.         move.w  d1,d3       ; move d1 to d3
33.         lsr.w   #8,d3       ; shift 8 bits right
34.         andi.w  #$F0,d3     ; leave only bits 7, 6, 5, and 4
35.         addi.w  #$10,d3     ; add $10 to d3
36.  
37.         andi.w  #$FFF,d1    ; filter out bits 15, 14, 13 and 12
38.         lsl.l   #5,d1       ; shift 5 bits left
39.         add.l   d6,d1       ; add the art address to d1
40.         move.w  d4,d2       ; move VRAM location to d2
41.         add.w   d3,d4       ; add d3 to VRAM address
42.         add.w   d3,d4       ; add d3 to VRAM address
43.  
44.         jsr QueueDMATransfer; Save it to the DMA queue
45.         dbf d5,DPLC_ReadEntry; repeat for number of requests
46.  
47. DPLC_End:
48.         rts         ; return

version 3:

Spoiler

Code (ASM):

1. LoadSonicDynPLC:
2.         moveq   #0,d0               ; quickly clear d0
3.         move.b  Current_Character.w,d0      ; get character ID
4.  
5.         movea.l Player_DPLCLoc(pc,d0.w),a2  ; put players DPLC location to a2
6.         move.l  Player_ArtLoc(pc,d0.w),d6   ; put players art location to a2
7.         move.w  #$F000,d4           ; offset in VRAM to store art
8.  
9.         moveq   #0,d0
10.         move.b  $1A(a0),d0  ; load frame number
11.         cmp.b   $FFFFF766.w,d0  ; check if equal with last queued frame
12.         beq.s   DPLC_End    ; if is, don't load new DPLC
13.         move.b  d0,$FFFFF766.w  ; remember queued frame
14. ; End of function LoadSonicDynPLC
15.  
16. ; ---------------------------------------------------------------------------
17. ; Subroutine to queue any pattern load cue
18. ; Input: a2 - DPLC file, d4 - VRAM address, d6 - Art file, d0 - frame number
19. ; ---------------------------------------------------------------------------
20.  
21. Load_DPLC:
22.         add.w   d0,d0       ; multiply by 2
23.         adda.w  (a2,d0.w),a2    ; get the right DPLC location
24.         moveq   #0,d5       ; quckly clear d5
25.         move.b  (a2)+,d5    ; then move the amount of requests to d5
26.         subq.w  #1,d5       ; subtract 1
27.         bmi.s   DPLC_End    ; if negative, branch away
28.  
29. DPLC_ReadEntry:
30.         moveq   #0,d1
31.         move.b  (a2)+,d1    ; get first byte to d1, and increment pointer
32.         lsl.w   #8,d1       ; shift 8 bits left
33.         move.b  (a2)+,d1    ; move second byte to d1
34.  
35.         move.w  d1,d3       ; move d1 to d3
36.         lsr.w   #8,d3       ; shift 8 bits right
37.         andi.w  #$F0,d3     ; leave only bits 7, 6, 5, and 4
38.         addi.w  #$10,d3     ; add $10 to d3
39.  
40.         andi.w  #$FFF,d1    ; filter out bits 15, 14, 13 and 12
41.         lsl.l   #5,d1       ; shift 5 bits left
42.         add.l   d6,d1       ; add the art address to d1
43.         move.w  d4,d2       ; move VRAM location to d2
44.         add.w   d3,d4       ; add d3 to VRAM address
45.         add.w   d3,d4       ; add d3 to VRAM address
46.  
47.         jsr QueueDMATransfer; Save it to the DMA queue
48.         dbf d5,DPLC_ReadEntry; repeat for number of requests
49.  
50. DPLC_End:
51.         rts         ; return

Next we need to create an array to store direct locations to art and DPLC data. It should be very simple, so I'll just show an example:

Code (ASM):

1. Player_DPLCLoc:     dc.l SonicDynPLC, TailsDynPLC
2. Player_ArtLoc:      dc.l Art_Sonic, Art_Tails

Put it right above LoadSonicDynPLC.

Great! Now your character loads its own art and DPLC.

Mappings

version 1:

Spoiler

Above Obj01, put this code:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Subroutine to set Player-specific variables
3. ; ---------------------------------------------------------------------------
4. SetPlayerDisplay:
5.         moveq   #0,d0           ; quickly clear d0
6.         move.b  Current_Character,d0    ; get character ID
7.         move.w  d0,d1           ; store to d1 as well
8.  
9.         lsl.w   #3,d0           ; shift left 4 bits
10.         add.w   d1,d0           ; add d1 to d0
11.         lea PlayerDataList(pc,d0.w),a1; get the table to a1
12.        
13.         move.l  (a1)+,Player_ArtLoc ; player art location
14.         move.l  (a1)+,4(a0)     ; get mappings
15.         move.l  (a1)+,Player_DPLCLoc    ; FPLC location
16.         move.l  (a1)+,Player_AniDat ; Animation data location
17.         move.l  (a1)+,PAni_Walk     ; walk animation
18.         move.l  (a1)+,PAni_Run      ; run  animation
19.         move.l  (a1)+,PAni_Roll     ; roll animation
20.         move.l  (a1)+,PAni_Roll2    ; roll animation
21.         move.l  (a1)+,PAni_Push     ; push animation
22.         rts             ; return

Next, we are going to create an array containing all this data. It's format is described in the comment.

Code (ASM):

1.         ;    Art file,  Map file,  DPLC file,   Ani file,     Walk ani ptr,  Run ani ptr,  Roll ani ptr,  Roll2 ani ptr,  Push ani ptr
2. PlayerDataList: dc.l Art_Sonic, Map_Sonic, SonicDynPLC, SonicAniData, SonAni_Walk,   SonAni_Run,   SonAni_Roll,   SonAni_Roll2,   SonAni_Push   ; Sonic
3.         dc.l Art_Tails, Map_Tails, TailsDynPLC, TailsAniData, TailsAni_Walk, TailsAni_Run, TailsAni_Roll, TailsAni_Roll2, TailsAni_Push ; Tails

Put it below SetPlayerDisplay. Next, at Obj01_Main and Obj09_Main replace:

Code (ASM):

1.         move.l  #Map_Sonic,4(a0)

with:

Code (ASM):

1.         bsr.w   SetPlayerDisplay

version 2:

Spoiler

Above Obj01, put this code:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Subroutine to set Player-specific variables
3. ; ---------------------------------------------------------------------------
4. SetPlayerDisplay:
5.         moveq   #0,d0           ; quickly clear d0
6.         move.b  Current_Character,d0    ; get character ID
7.         lsl.w   #2,d0           ; shift left 2 bits
8.         lea PlayerDataList(pc,d0.w),a1; get the table to a1
9.        
10.         move.l  (a1)+,Player_ArtLoc ; player art location
11.         move.l  (a1)+,4(a0)     ; get mappings
12.         move.l  (a1)+,Player_DPLCLoc    ; FPLC location
13.         move.l  (a1),Player_AniDat  ; Animation data location
14.         rts             ; return

Next, we are going to create an array containing all this data. It's format is described in the comment.

Code (ASM):

1.         ;    Art file,  Map file,  DPLC file,   Ani file
2. PlayerDataList: dc.l Art_Sonic, Map_Sonic, SonicDynPLC, SonicAniData    ; Sonic
3.         dc.l Art_Tails, Map_Tails, TailsDynPLC, TailsAniData    ; Tails

Put it below SetPlayerDisplay. Next, at Obj01_Main and Obj09_Main replace:

Code (ASM):

1.         move.l  #Map_Sonic,4(a0)

with:

Code (ASM):

1.         bsr.w   SetPlayerDisplay

version 3:

Spoiler

At Obj01_Main and Obj09_Main replace:

Code (ASM):

1.         move.l  #Map_Sonic,4(a0)

with:

Code (ASM):

1.         moveq   #0,d0           ; quickly clear d0
2.         move.b  Current_Character.w,d0  ; get character ID
3.  
4.         move.l  #Player_MapLoc,a1   ; get players mapping location array
5.         add.l   d0,a1           ; get correct mapping for player
6.         move.l  (a1),4(a0)      ; put it to Sonic's mappings

Now we need table for mappings. This, again, isnt all that complicated, so have an example:

Code (ASM):

1. Player_MapLoc:      dc.l Map_Sonic, Map_Tails

Place it above Obj01.

Animations

version 1:

Spoiler

First, go to Sonic_Animate, and replace:

Code (ASM):

1.         lea (SonicAniData).l,a1

With this:

Code (ASM):

1.         move.l  Player_AniDat.w,a1

Now, at loc_13A9C, replace:

Code (ASM):

1.         lea (SonAni_Run).l,a1 ; use running animation
2.         cmpi.w  #$600,d2    ; is Sonic at running speed?
3.         bcc.s   loc_13AB4   ; if yes, branch
4.         lea (SonAni_Walk).l,a1 ; use walking animation

With:

Code (ASM):

1.         move.l  PAni_Run.w,a1       ; use running animation
2.         cmpi.w  #$600,d2        ; is Sonic at running speed?
3.         bcc.s   loc_13AB4       ; if yes, branch
4.         move.l  PAni_Walk.w,a1      ; use walking animation

Go to loc_13ADE, and replace:

Code (ASM):

1.         lea (SonAni_Roll2).l,a1 ; use fast animation
2.         cmpi.w  #$600,d2    ; is Sonic moving fast?
3.         bcc.s   loc_13AF0   ; if yes, branch
4.         lea (SonAni_Roll).l,a1 ; use slower animation

With:

Code (ASM):

1.         move.l  PAni_Roll2.w,a1 ; use fast animation
2.         cmpi.w  #$600,d2    ; is Sonic moving fast?
3.         bcc.s   loc_13AF0   ; if yes, branch
4.         move.l  PAni_Roll.w,a1  ; use slower animation

Go to loc_13B26, and replace:

Code (ASM):

1.         lea (SonAni_Push).l,a1

With:

Code (ASM):

1.         move.l  PAni_Push.w,a1  ; use pushing animation

version 2:

Spoiler

First, go to Sonic_Animate, and replace:

Code (ASM):

1.         lea (SonicAniData).l,a1

With this:

Code (ASM):

1.         move.l  Player_AniDat.w,a1

Now, at loc_13A9C, replace:

Code (ASM):

1.         lea (SonAni_Run).l,a1 ; use running animation
2.         cmpi.w  #$600,d2    ; is Sonic at running speed?
3.         bcc.s   loc_13AB4   ; if yes, branch
4.         lea (SonAni_Walk).l,a1 ; use walking animation

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Run(pc,d4.w),a1    ; put players running animation to a1
4.  
5.         cmpi.w  #$600,d2        ; is Sonic at running speed?
6.         bcc.s   loc_13AB4       ; if yes, branch
7.         movea.l PAni_Walk(pc,d4.w),a1   ; put players walking animation to a1

Go to loc_13ADE, and replace:

Code (ASM):

1.         lea (SonAni_Roll2).l,a1 ; use fast animation
2.         cmpi.w  #$600,d2    ; is Sonic moving fast?
3.         bcc.s   loc_13AF0   ; if yes, branch
4.         lea (SonAni_Roll).l,a1 ; use slower animation

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Roll2(pc,d4.w),a1  ; put players fast rolling animation to a1
4.  
5.         cmpi.w  #$600,d2        ; is Sonic moving fast?
6.         bcc.s   loc_13AF0       ; if yes, branch
7.         movea.l PAni_Roll(pc,d4.w),a1   ; put players slow rolling animation to a1

Go to loc_13B26, and replace:

Code (ASM):

1.         lea (SonAni_Push).l,a1

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Push(pc,d4.w),a1   ; put players fast rolling animation to a1

Just above SAnim_RollJump, we make few arrays. They are pretty simple so I'll show an example:

Code (ASM):

1. PAni_Run:   dc.l SonAni_Run,    TailsAni_Run
2. PAni_Walk:  dc.l SonAni_Walk,   TailsAni_Walk
3. PAni_Roll2: dc.l SonAni_Roll2,  TailsAni_Roll2
4. PAni_Roll:  dc.l SonAni_Roll,   TailsAni_Roll
5. PAni_Push:  dc.l SonAni_Push,   TailsAni_Push

version 3:

Spoiler

First, go to Sonic_Animate, and replace:

Code (ASM):

1.         lea (SonicAniData).l,a1

With this:

Code (ASM):

1.         moveq   #0,d0           ; quickly clear d0
2.         move.b  Current_Character.w,d0  ; get character ID
3.         movea.l Player_AniDat(pc,d0.w),a1   ; put players animation data to a1

Above Sonic_Animate, put array. This is pretty simple so here is example:

Code (ASM):

1. AniDat:     dc.l SonicAniData, TailsAniData

Now, at loc_13A9C, replace:

Code (ASM):

1.         lea (SonAni_Run).l,a1 ; use running animation
2.         cmpi.w  #$600,d2    ; is Sonic at running speed?
3.         bcc.s   loc_13AB4   ; if yes, branch
4.         lea (SonAni_Walk).l,a1 ; use walking animation

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Run(pc,d4.w),a1    ; put players running animation to a1
4.  
5.         cmpi.w  #$600,d2        ; is Sonic at running speed?
6.         bcc.s   loc_13AB4       ; if yes, branch
7.         movea.l PAni_Walk(pc,d4.w),a1   ; put players walking animation to a1

Go to loc_13ADE, and replace:

Code (ASM):

1.         lea (SonAni_Roll2).l,a1 ; use fast animation
2.         cmpi.w  #$600,d2    ; is Sonic moving fast?
3.         bcc.s   loc_13AF0   ; if yes, branch
4.         lea (SonAni_Roll).l,a1 ; use slower animation

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Roll2(pc,d4.w),a1  ; put players fast rolling animation to a1
4.  
5.         cmpi.w  #$600,d2        ; is Sonic moving fast?
6.         bcc.s   loc_13AF0       ; if yes, branch
7.         movea.l PAni_Roll(pc,d4.w),a1   ; put players slow rolling animation to a1

Go to loc_13B26, and replace:

Code (ASM):

1.         lea (SonAni_Push).l,a1

With:

Code (ASM):

1.         moveq   #0,d4           ; quickly clear d0
2.         move.b  Current_Character.w,d4  ; get character ID
3.         movea.l PAni_Push(pc,d4.w),a1   ; put players fast rolling animation to a1

Just above SAnim_RollJump, we make few arrays. They are pretty simple so I'll show an example:

Code (ASM):

1. PAni_Run:   dc.l SonAni_Run,    TailsAni_Run
2. PAni_Walk:  dc.l SonAni_Walk,   TailsAni_Walk
3. PAni_Roll2: dc.l SonAni_Roll2,  TailsAni_Roll2
4. PAni_Roll:  dc.l SonAni_Roll,   TailsAni_Roll
5. PAni_Push:  dc.l SonAni_Push,   TailsAni_Push

Congratulations! Now you should have extra character in your hack! If you have any trouble, please look into troubleshooting section prior to asking any questions.

Troubleshooting

Spoiler

Garbled graphics/parts of graphics

Spoiler

This is due to your characters art being inbetween 2 128KB ROM "banks". VDP can only DMA from one bank per transfer, and because of this the art can only lie on one bank. You can put align $20000 just before the art file causing issue. Note: This will put 00's until next address dividable by 131072 (0x20000). Here is an example:

Code (ASM):

1. ; ---------------------------------------------------------------------------
2. ; Uncompressed graphics - Sonic
3. ; ---------------------------------------------------------------------------
4. Art_Sonic:  incbin  artunc\sonic.bin    ; Sonic
5.         even
6. ; ---------------------------------------------------------------------------
7. ; Uncompressed graphics - Tails
8. ; ---------------------------------------------------------------------------
9.     align   $20000  ; align to next bank
10. Art_Tails:  incbin  artunc\tails.bin    ; Tails' art
11.         even

Sometimes graphics don't update

Spoiler

I suggest following this guide, and trying again.