Mini-tutorials Thread

Went ahead and pinned the thread, as I can see this gaining some traction & being popular with newcomers.

 

(This is technically a repost, but since the old thread has been moved to the archives, it felt fitting to have that one-liner in here as well.)

Basically, when you roll really, really fast into a Caterkiller from Marble Zone and Scrap Brain Zone, you will still get damaged despite having destroyed it. In the original game this wasn't really much of a noticable issue, since the locations where you can even gain enough speed to roll this fast are scarce, if they exist at all. But nowadays, the spin dash is everywhere and it's very easy to bash head-on right into a Caterkiller at mach speed at any time.

The issue is that the spiked body segments don't get deleted immediately when destroying the head, but rather 1 frame later. So if you happen to roll fast enough to travel the distance to the body in that single frame, you still get damaged.

Fixing it literally takes a single line. Go to loc_16C7C and add this below the label:

Code:

       clr.b    $20(a1)

Now, when the head gets destroyed, all touch response values (which are responsible for objects being solid, breakable, damaging, etc.) from the body spikes are getting set to 0, which essentially means harmless and without collision. This is more straight forward than deleting all the body segments immediately, though that would obviously work as well.

 

If you have added the Spindash, heed this warning if you intend for any of your levels to be longer than 64 256x256 chunks, or 128 128x128 chunks.

(I'll be using GitHub here, as it's where I had to face this issue).

If you just added horizontal scroll delay, MoveScreenHoriz, at the top, should look like this:

Code:

MoveScreenHoriz:
        move.w    (Horiz_scroll_delay).w,d1
        beq.s    @cont1
        subi.w    #$100,d1
        move.w    d1,(Horiz_scroll_delay).w
        moveq    #0,d1
        move.b    (Horiz_scroll_delay).w,d1
        lsl.b    #2,d1
        addq.b    #4,d1
        move.w    (v_trackpos).w,d0
        sub.b    d1,d0
        lea    (v_tracksonic).w,a1
        move.w    (a1,d0.w),d0
        and.w    #$3FFF,d0
        bra.s    @cont2

See that and? S3K increased it to 7FFF. Why? Because otherwise, the scroll delay completely breaks past 64 256x256 chunks, or 128 128x128 chunks. So, if your levels are going to be bigger than 64 256x256 chunks, or 128 128x128 chunks, then change that and.

(Note that this would only be possible if you modified the level layout format.)

 

S3K-Esque Act Clear Timing
If for some reason you want the Act Clear music to play when the results tallies are fully positioned on screen, like with Sonic 3 and Knuckles, here's how this can be done. It can go alongside DeltaWooloo's switched around results layout thingy. This is meant for the 2005 Hivebrain disassembly, but I'm sure a similar concoction can be made in the GitHub disassembly.

Head to loc_ECD0 in sonic1.asm and you'll notice a command for 8E to be played when the signpost stops spinning. Change the 8E to E0, which is the fade out command.
Next, go to Obj3A_ChkPos and underneath the neg.w d1 line, insert this:

That way when the act result screen tallies are all in place (has passed text, time/ring bonus tally, etc.), the act clear song will play. For the special stage results, the same applies. Delete the lines of code calling for #$8E to be played in loc_47D4. And when you get to Obj7E_ChkPos, you'd add those two lines that call for the song to play when all the tallies are displayed, right underneath the same neg.w d1 line.

Not sure if this has been conducted before or properly well constructed, but if anyone's got feedback for how this can be better, lemme know. Thanks in advance!

 

This is a nice short and easy thing actually but I guess it's more of a personal preference (as you mentioned in it as well).

 

Unsure if it's mini enough, but oh well.

Separate Boss Music Tracks

One thing to bring up is that you'll need to follow this guide to get started:
http://info.sonicretro.org/SCHG_How-to:Expand_the_music_index_from_$94_to_$9F
This can expand the music index to allow more tracks, either all the way to 9F or to a limit of your choice.

First, get some boss music ported to Sonic 1's SMPS driver (modded 68K DAC Type 1B) with SMPSConv. At least four tracks will do considering the GHZ and FZ bosses. If you port five tracks, check out the last optional step for a cute bonus. Include the tracks in the MusicIndex and the incbin Music lines near the end of sonic1.asm.
The former looks like this:

Code:

MusicIndex:    dc.l Music81, Music82
        dc.l Music83, Music84

(the rest of the tracks are there, trust me)

The latter would look like this, with 8C as an example:

Code:

Music8C:    incbin    sound\music8C.bin
        even

Now let's get to the meat of this guide. The header Resize_GHZ3boss has a command to play the boss music which is at the start of loc_6ED0, and similar loc's are present with the Resize_boss headers for other zones. These all would use 8C due to it being the primary boss track. The section of the code would be this:

Code:

        move.w    #$8C,d0
        bsr.w    PlaySound    ; play boss music

With the four additions to the music index, use the added songs' digits in place of 8C, mainly with the MZ, SYZ, SLZ, and LZ Resize_boss sections of code. Final Zone uses a different track anyway, so it would be pointless to redirect it.

BONUS: If you added a fifth song as part of the SBZ 2 to 3 cutscene, the same can be done under Obj3A_SBZ2.

Much like my last mini-guide, a similar concoction can be done in the GitHub disassembly as I've used Hivebrain '05. No credit is required for this one, unless it's for whoever made the songs you're porting. Thanks!

 

I think I have a sort-of tutorial. (For github disasm)

HOW TO CHANGE YOUR ROM'S HEADER

Very simple. Look for these lines in Sonic.asm:
Title_Local: dc.b "SONIC THE HEDGEHOG " ; Domestic name
Title_Int: dc.b "SONIC THE HEDGEHOG " ; International name
Change the text in the parenthesis to whatever you like.
Pointless, but felt like pointing it out.

 

Implement the Shrinking animation for losing Special Stages in S1

A quirk of S1 beta remakes that I did find interesting was utilizing an unused animation for Sonic in some areas. For example, one remake uses the shrink animation for when you lose a special stage (touching the Goal block anyway). This lil guide will show you how to include that animation. Look for Obj09_GOAL inside the sonic1.asm file, and under the move.w command for "change item" plop this line of code underneath:

Code:

        move.b    #$19,$1C(a0)    ; use "shrinking" animation

This will ensure for when you touch the Goal block, the shrink animation plays. Like before, this is with the Hivebrain 05 disassembly, but a workaround could be crafted with the GitHub version. Cheers!

 

Actually, you can't just put whatever there. If I remember correctly, the amount of characters in the header is 48. I don't know why, I just know that's how it is. In most emulators, it'll show this, instead of Sonic The Hedgehog.

"SONIC THE HEDGEHOG "

A fix for this, however is just adding spaces until you reach 48 characters, or cutting down on some (if you have more than 48).

 

Sorry for double posting but I feel like this is better off here than it's own thread.
Working With Special Stages in Sonic 1
This allows you to change the speed of the stages.

Hivebrain

Code:

        move.w    #$40,($FFFFF782).w ; set stage rotation    speed

Github

Code:

        move.w    #$40,(v_ssrotate).w ; set stage rotation speed

See these lines? They set the rotation speed in the special stage, which is set to 40 by default.

For example, If I wanted to make the special stages rotate a bit faster, I could change the speed from 40 to 50, or if I didn't want them to rotate at all, I could either set the value to zero, or remove the line entirely (though I don't recommend it).

 

Okay, so this has always annoyed me when altering Sonic 3 and Knuckles (or just playing Sonic Classic Heroes, which reused the same code). When the screen flashes it makes sure to keep the black on the transparency colour for PAL/Overscan users, which most other Genesis games did during this time. However, it does limit background colours, optimisation and potential layering (Look at Aquatic Ruins leaves for example). That, and the game uses this colour by mistake anyway! So let's fix this issue. Just note that with water, only Hydrocity separates the transparency colour properly

For Hyper Sonic the flash data is at VInt_8. It should look like this

Code:

        stopZ80
        bsr.w    Poll_Controllers
        tst.b    (Hyper_Sonic_flash_timer).w
        beq.s    VInt_8_NoFlash

        ; flash screen white when Hyper Sonic's double jump move is used
        subq.b    #1,(Hyper_Sonic_flash_timer).w
        lea    (VDP_data_port).l,a6
        move.l    #vdpComm($0000,CRAM,WRITE),(VDP_control_port).l
        move.w    #$EEE,d0
        move.w    #$1F,d1
-
        move.w    d0,(a6)
        dbf    d1,-    ; fill entire first and second palette lines with white
        move.w    #0,(a6)    ; keep backdrop black
        move.w    #$1E,d1
-
        move.w    d0,(a6)
        dbf    d1,-    ; fill remaining colours with white
        bra.s    VInt_8_Cont

Even to a guy who can't read Assembly like myself, the issue is pretty obvious. It fills the object art completely, then stops at the start of the third palette (which the Sonic Engine uses as it's transparent colour) and continues

1: Remove these lines, they're unnecessary after the fix

Code:

        move.w    #0,(a6)    ; keep backdrop black
        move.w    #$1E,d1
-
        move.w    d0,(a6)
        dbf    d1,-    ; fill remaining colours with white

2: change $1F to $3F, this fills the entire palette with white

Code:

        move.l    #vdpComm($0000,CRAM,WRITE),(VDP_control_port).l
        move.w    #$EEE,d0
        move.w    #$1F,d1

And... yeah, that's it for Hyper Sonic

Now, when the Lightning shield goes into water it uses different code. We're just going to do the same for Obj_Lightning_Shield_FlashWater, which should look like this

Code:

Obj_Lightning_Shield_FlashWater:
        move.l    #Obj_Lightning_Shield_DestroyUnderwater2,(a0)
        andi.b    #$8E,status_secondary(a2)    ; Sets Status_Shield, Status_FireShield, Status_LtngShield, and Status_BublShield to 0

        ; Flashes the underwater palette white
        lea    (Water_palette).w,a1
        lea    (Target_water_palette).w,a2
        move.w    #($80/4)-1,d0            ; Size of Water_palette/4-1

loc_197F2:
        move.l    (a1),(a2)+            ; Backup palette entries
        move.l    #$0EEE0EEE,(a1)+        ; Overwrite palette entries with white
        dbf    d0,loc_197F2            ; Loop until entire thing is overwritten

        move.w    #0,-$40(a1)            ; Set the first colour in the third palette line to black
        move.b    #3,anim_frame_timer(a0)
        rts

...nevermind, it's even easier, just remove this

Code:

move.w    #0,-$40(a1)            ; Set the first colour in the third palette line to black

There are probably more examples of this, but these are the easiest to do on command

 

Disabling the Sparkles from the Signpost

Want to give the signposts in your Sonic hacks a little CD esque flavor? For those who prefer when there's no sparkles surrounding the signpost when you twirl it, here's how you do it. It does not require erasing the sprites for the ring sparkles or any complicated shit like that, it's an insanely easy ASM tweak.
Head down to Obj0D_Sparkle in sonic1.asm and you'll see these two lines of code:

Code:

        move.b    #$25,0(a1)    ; load rings object
        move.b    #6,$24(a1)    ; jump to ring sparkle subroutine

For GitHub disassembly users, take out these two lines of code in "0D Signpost.asm" which is in the _incObj folder:

Code:

        move.b    #id_Rings,0(a1)    ; load rings object
        move.b    #id_Ring_Sparkle,obRoutine(a1) ; jump to ring sparkle subroutine

All you have to do is remove these lines. Just that simple. No credit is required at all due to how easy this is.

 

Adding Sonic 2's level select in Sonic 1 on
MACRO ASSEMBLER AS DISASSEMBLIES!

If you're wanting to port Esrael's Sonic 2 level select in the AS versions of Sonic 1, you realize that it's not compatible for Macro Assembler AS,
as it was originally designed for Sonic 1's ASM68K disassemblies. Well, this simple and easy tutorial shows you how to do it.
These steps will also apply to Sonic Retro's tutorial. Credit goes to Esrael L.G. Neto.

STEP 1: Download the S2 level select file.

s2menu_AS.zip

STEP 2: Extract the files and then insert them into your disassembly.

STEP 3: Open "sonic.asm" and go to the very bottom, and right under "; end of 'ROM'" add this line:

Code:

; end of 'ROM'
        even
EndOfRom:    include "s2_menu.asm"  <-- add this line!

        END

STEP 4: Go to "Tit_ChkLevSel" and add a line between "beq.w PlayLevel" and "moveq #palid_LevelSel,d0".

Code:

Tit_ChkLevSel:
        tst.b    (f_levselcheat).w ; check if level select code is on
        beq.w    PlayLevel    ; if not, play level
        btst    #bitA,(v_jpadhold1).w ; check if A is pressed
        beq.w    PlayLevel    ; if not, play level
        jmp    (Level_Select_Menu).l    ; if yes, go to Sonic 2 level select
        moveq    #palid_LevelSel,d0
        bsr.w    PalLoad2    ; load level select palette
        lea    (v_hscrolltablebuffer).w,a1
        moveq    #0,d0
        move.w    #$DF,d1

STEP 5 (FINAL): And lastly, go to the "_inc" folder and open "Palette Pointers,"
which contains all of the color palette IDs and addresses.

Go to the lines "ptr_Pal_Ending:" and "even" and right between both of them, add this line:

Code:

ptr_Pal_Menu:        palp    Pal_Menu,v_pal_dry,$40        ; $14 (20) - Sonic 2 level select
            even

And you're done! Enter the level select code and this is the result you should get:


The source code with all of these steps applied is available here:

 

CD Esque Explosion Animations

This is another one of those insanely easy tweaks for animations when you know what you're doing. In this case, we're gonna make a slight adjustment to the explosion animations (monitors, badniks, bosses) in Sonic 1. Specifically, we're adjusting the speed to resemble how they animated in Sonic CD.

HIVEBRAIN:

Head over to Obj27_Animate in sonic1.asm. This is due to how there aren't anim asm files for the explosions. The first line of code is this:

Code:

        subq.b    #1,$1E(a0)    ; subtract 1 from frame    duration

Just replace 1 with 2 and you're set.

GITHUB:

Head over to the "24, 27 & 3F Explosions.asm" file in the _incObj folder. Scroll down until you reach ExItem_Animate. You will see this as the first line of code in this section.

Code:

        subq.b    #1,obTimeFrame(a0) ; subtract 1 from frame duration

Just replace 1 with 2 and you're good to go.

No credit required.

 

MAKE THE TITLE SCREEN USE ITS OWN BG DEFORMATION ROUTINES (Sonic 1 Github)
So you want to make the title screen for your hack be something other than the scrolling BG of Green Hill, eh? I'll assume you've already made the title screen load its own artwork and mappings. If you haven't, then trundle over to the Sonic Retro wiki and follow this tutorial first!
Okay, so open up "_inc/DeformLayers (JP1).asm" and go to the label "Deform_GHZ". Immediately after the label, add this:

Code:

        cmpi.b    #id_Title,(v_gamemode).w
        beq.w    Deform_Title

Deform_GHZ_Stage:

Next, Before the label "Deform_LZ", add your new background deform routine here with the label "Deform_Title". Don't have one in mind and just want some simple scrolling? You can just take the "Deform_LZ" routine from the REV00 code and use that instead (just make sure to change the branch that goes to "ScrollBlock1" to instead go to "BGScroll_XY")

If you're using REV00 (why??), then instead open up "_inc/DeformLayers.asm" and do the same edits; if you're going to be using simple BG scrolling here you can omit adding a new label and deform routine and just go to LZ's. I used LZ's REV00 code in REV01 because it's simpler.