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In case you haven't seen the Sheet or the Glitches and Bugs guide today, I have great news; I was finally able to break the Sketch bug down and control when it occurred yesterday!

Now it's time to make a better explanation for the bug. I still dunno how the writeup should be done on this for the guide, hence the long post here to make up for the lack of quality on the Sheet at the moment. A miniguide might come up later today.

Onto the bug! First we'll get the non-right-over-your-head explanation out of the way then get to the technical explanation for why this happens.

The reason this occurs is because a missed Sketch attempt will cause the game to load bad sprite data. You see, it doesn't matter if Sketch misses or not, the game will still load a sprite for any Sketch attempt. However, on missed attempts, the game will go completely off-track and load from offsets it really shouldn't be loading from.

The first mistake it makes is loading pointer data for the monster sprite. When Sketch misses in FF3us v1.0 and FF6j, it gets a 16-bit pointer value from 7E:20FF. What is this exactly?

The first character's in-battle Magic list, specifically, spell 28:

7E20FE: Spell index
7E20FF: Unknown (starts at 7F in battle, changes with status lost?), bit 7 = spell availability (1 = greyed out)
7E2100: Spell aiming
7E2101: MP cost

The bolded part is what we're looking at specifically. 7E:20FF can change with spells cast by the first character (no one else can change it thankfully), so it would be best the the first character do nothing besides maybe the missed Sketch if you're looking for a bug exploit. Once the game loads this and calculates a pointer value from it, anything could happen. Most of the time it does nothing, but there are specific cases where the game will go haywire.

Example: Take a character who knows all the Magic spells in the game (or most of them will probably work just as well, we only need spell 28) and put them in the first slot. Go to the Config menu and set Magic Order to 3 (second Config page, scroll down in Config to find it). This will put Mute in slot 28, both out of and in battle. Enter battle and do not move the first character (unless, as I said, they have Sketch). Now make Sketch miss (Vanish an enemy, have a low level, whatever). Depending on the monsters you're fighting, you may or may not be able to escape battle, it might even reset or crash on you. Try this on Dark Winds or Tumbleweeds, they seem friendly towards the bug. Once this is executed, you should have a few Economizers, Gem Boxes, and Scimitars, etc. IIRC, along with the fourth character having a Fenix Down in their right hand slot (don't use it as a weapon, it crashes the game and emulators). The graphic glitches shouldn't last beyond the battle.

As of right now, I could use more spells that can cause the Sketch bug. The only other one I have is the above with the first character as an Imp (that one will give you 28 Tempests, Wind God fans rejoice! ). The effects on the Item inventory are always the same, so you could use this, see which slots are affected, and move items out of the way so as to not overwrite anything valuable when you retry the bug.

In short, all you need to know to make this work is that you need the right spell in slot 28 of the first character's in-battle Magic menu and then proceed to miss with Sketch. That's it. Mute is just one example, but that's all I have for now.

Now to the technical explanation, i.e. the above reworded with assembly code and crap.

The function at C2/F5D2 ultimately is the function responsible for the bug. Here's the function as it appears in FF3us:

Code

C2:F5D2 A0 00 28        LDY #$2800
C2:F5D5 22 09 B1 C1     JSL $C1B109
C2:F5D9 AD 8D 89        LDA $898D
C2:F5DC 29 FE           AND #$FE
C2:F5DE 8D 8D 89        STA $898D
C2:F5E1 A0 03 00        LDY #$0003
C2:F5E4 B1 76           LDA ($76),Y
C2:F5E6 0A              ASL
C2:F5E7 AA              TAX
C2:F5E8 C2 20           REP $20
C2:F5EA BD 01 20        LDA $2001,X
C2:F5ED AA              TAX
C2:F5EE 7B              TDC
C2:F5EF E2 20           SEP $20
C2:F5F1 22 D1 24 C1     JSL $C124D1
C2:F5F5 4C 09 F8        JMP $F809

The problem lies at C2:F5E4. In the traces, the value loaded was from 7E:2D71. This is usually some low 8-bit value, if not zero. However, when Sketch misses, it returns a FFh value. That's where the Sketch bug begins. How was I able to tell? LDA $2001,X appears like this in the traces:

Code

$C2/F5EA: BD 01 20     LDA $2001,X [$7E:20FF]    A:00FE X:00FE Y:0003 D:0000 DB:7E S:15CE P:envmxdIzC

Note the $7E:20FF. Do you recognize it? No? It's the 28th spell in the first character's in-battle Magic list. Specifically, an unknown byte and the spell's aiming byte (the first post has the Magic list format). They now make up a bad 16-bit value to be used in sprite loading from the X register. Here's how, beginning with the value reloaded from scratchpad RAM and ending with a size/palette loadup (sprites and moulds are loaded soon after this):

Code

$C1/24F7: A5 10        LDA $10 [$00:0010]        A:0000 X:1000 Y:0003 D:0000 DB:7E S:15C7 P:envmxdIZC
$C1/24F9: 0A           ASL A                     A:417F X:1000 Y:0003 D:0000 DB:7E S:15C7 P:envmxdIzC
$C1/24FA: 0A           ASL A                     A:82FE X:1000 Y:0003 D:0000 DB:7E S:15C7 P:eNvmxdIzc
$C1/24FB: 18           CLC                       A:05FC X:1000 Y:0003 D:0000 DB:7E S:15C7 P:envmxdIzC
$C1/24FC: 65 10        ADC $10 [$00:0010]        A:05FC X:1000 Y:0003 D:0000 DB:7E S:15C7 P:envmxdIzc
$C1/24FE: AA           TAX                       A:477B X:1000 Y:0003 D:0000 DB:7E S:15C7 P:envmxdIzc
$C1/24FF: BF 02 70 D2  LDA $D27002,X [$D2:B77D]  A:477B X:477B Y:0003 D:0000 DB:7E S:15C7 P:envmxdIzc

$D2:B77D is where the real trouble can begin. That address is well beyond the monster sprite pointers and is in some hole in the ground elsewhere. Along with the rest of the monster sprite pointer data, Sketch's missed effect will now be determined by the bad data the game just loaded up. In the case shown here, it WILL be broken. 417Fh is a dangerous value to the FF3us system that once converted and used to pick up the sprite data, will cause the Sketch bug to occur. You should end up with several Gem Boxes and Scimitars from this glitch, if you're able to survive the fight. And do beware the fourth character's right hand slot, it will contain a Fenix Down after this bug has been executed.

But how do we control what spell appears in slot 28? Normally, the only spell that appears there is X-Zone, though while learning spells, the spell list may sometimes appear in a more compressed format so there aren't long gaps between spells. That's one way of doing it. Other ways include the Magic Order option in the Config menu. For the glitch above, try setting it to 3 (Attack, Effect, Healing) and putting a character who knows all spells in the first character slot. Mute will now appear in slot 28, and with that you can glitch the game.

I'm not too clear about the unknown byte though. It appears in the trace above as the 7F in 417Fh (the 41 is the aiming byte). What I do know is that bit 7 controls whether a spell will be available to you or not. You can manipulate this yourself by setting Imp status, and in this particular case (Mute at slot 28), you can get a variant of the bug listed that will yield 28 Tempests and make one of your characters look like Leo for the rest of the battle (I believe the second character). The exact value loaded for that from 7E:20FF is 41FFh. The rest of the bits seem to be manipulated by the spells the first character uses. I have yet to figure out how and why it works, plus what spells manipulate it, but I do know most status spells and Rasp will affect it. If the first character doesn't do anything though, that byte will never change from its default setting of 7Fh. The first character can use Sketch without manipulating that byte though (well, so long as its a missed attempt, dunno about hits).

And finally, what was the fix Square put in for v1.1? A check for the Negative flag, of course!

Code

C2:F5E4 B1 76        LDA ($76),Y
C2:F5E6 10 05        BPL $F5ED
C2:F5E8 A2 FF FF     LDX #$FFFF
C2:F5EB 80 0B        BRA $F5F8

What this does specifically is make the game accept FFFFh as the value it will calculate the pointer value for the monster sprite from whenever Sketch misses. With this in place, v1.1 will never see the Sketch bug.

Unless, of course, you use this PAR code to make the game skip the fix entirely:

C2F5E680

And now v1.1 will see the Sketch bug in all its glory. I dunno what this code will do to v1.0 so don't try it until you're dead certain what version you have.

How do you do that? Use the method for triggering the bug I just presented! Since the Sketch bug is guaranteed if you execute the method correctly (which isn't difficult at all once you understand how), you can now use it to determine what version you have without hacking. For clarification, I'll relist it, with all precautions in place (of course, if your game is erased, don't come crying to me, the Sketch bug is a risky move that has reportedly erased saves before so try at your own risk):

1. Get a character that knows all spells and put him in the first character slot.
2. Set Magic Order to 3: Attack, Effect, Healing. Mute should now be in slot 28 in battle.
3. Don't move the first character and set yourself up for a missed Sketch attempt (Vanish, low levels, whatever you need to do).
4. Sketch and miss. Doesn't matter if the first character Sketches, so long as it misses. Voila. Bug. As stated before, Dark Winds and Tumbleweeds seem to work well with this.

As for FF6j, the bug SEEMS to exist in that version, but the bad sprite data didn't cause it to glitch (the data FF6j loads is different from FF3us). If it exists at all, then the values that will cause this damning error are simply undiscovered.

Thoughts? Spell submissions? Utterly confused? Then reply. Especially if you have spell submissions.

--------------------

The Unoriginal White Sheet

-Master ZED

Excellent work, ZED. You truly are our FF6 god.

The only problem I had was with "affect" being used instead of "effect"...

--------------------

~Status Report~

* Completed... Dragon's Head
* Completed... Soldiers of the Empire: Disciples (release pending)
* In Progress/Undecided... Of Love and Betrayal
* Planning/Assembly... Where it all Began

I...don't know what to say. Part of me is glad that the Sketch bug is finally something I can add to my ever-growing knowledge. But the other part tells me that today is the day that everything that is worth mentioning has been broken down.

This is like eating the last cookie. Tasty, sure. But also the last, a fact that leans more on your soul then the joy of your taste buds.

But all in all, I indeed heard that the bug was put in accidentaly in the transfer from Japan to the States. I can't help you with the spells, since today is one of those fine days that I have no access to the game.


This post has been edited by Djibriel on 22nd June 2004 14:52

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The Collapse of Heaven and Earth

OK, it may not always be what spell you have so much as who you use it against. Tumbleweed and Dark Wind gave similar results, but a test against a Clear Zone Eater yielded Illuminas, along with the desrtuction of my Relic inventory because that's where it just so happened to place alot of the crap it gave me. ^_^'

So I guess my focus will switch from "what spells?" to "who to glitch?". I'll still accept spell submissions, though admittedly I was getting nowhere with those once I left Mute and its Imp status variation.

So get something interesting against a certain monster? Post it here!

And remember, test on an emulator. I don't want any horror stories about people frying their carts doing this.

--------------------

The Unoriginal White Sheet

-Master ZED

Does this mean anything to use who don't have the ability to hack? Can we use this to our advantage on our SNES? I would really like to know thanks!

--------------------

"Look at me! I'm a receptionist! G'fa ha ha!" Quote Ultros

Yes. What he just explained is how to perform the bug yourself, without fail, no matter which way you're playing the game. I won't bother restating the procedure, so just scroll back up to the four steps listed at the end of his first post.

This post has been edited by Zephir on 23rd June 2004 02:42

--------------------

~Status Report~

* Completed... Dragon's Head
* Completed... Soldiers of the Empire: Disciples (release pending)
* In Progress/Undecided... Of Love and Betrayal
* Planning/Assembly... Where it all Began

Quote (Djibriel @ 22nd June 2004 09:51)

But all in all, I indeed heard that the bug was put in accidentaly in the transfer from Japan to the States.

Well, Assassin has just confirmed that this explanation is both true and *potentially* false. When looking at FF6j, the only thing stopping the Sketch bug from showing up that I could tell was that the same bad values that cause the Sketch bug in FF3us load something different in FF6j that doesn't cause the bug (which was confirmed in the traces). However, a little hacking has proven that the bug does exist in FF6j, even if the aiming values discovered to cause it so far don't exist in the actual game.

And because of that last reason, I can't add the Sketch bug as a two version (FF6j/FF3us v1.0) bug yet.

EDIT:

Another note on Zone Eater:

While you can safely execute the bug against him and get yourself a stack of Illuminas, do not let him Engulf your entire party if you use the bug. You'll be transported to Gogo's cave as usual, but the Sketch bug will cause a strange error that will effectively freeze the game.

Another general note:

You can execute the bug more than once per battle. Even better, the same effects on the Item inventory will occur, so if you get an item you like from the bug, move it to an unaffected slot, and execute the bug again the same battle, you can continue to replicate that item as many times as you want. I don't know how safe this will be for all enemies, though Zone Eater didn't seem to mind a repeat attempt.

EDIT 2: The Engulf bug should read as follows; Zone Eater is NOT safe because as soon as you step into a town, dungeon, etc., the game glitches and effectively freezes. Should have tested this more before I said anything....

This post has been edited by Master ZED on 23rd June 2004 16:58

--------------------

The Unoriginal White Sheet

-Master ZED

Thank you for the clarification, I scrolled through all those charts of code and was confused.

Now for my next question, your steps are easy enough to follow, except: What did you mean about clearing the spot of the item you like? Move the item in your equipment menu? You called it "the uneffected slot."

Does mute being in the 28th magic spot have anything special to do with the glitch, or just a trigger?

And finally, when you get the items after, do they appear in the things you won, or you just have them? I and everyone else thanks you again!!

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"Look at me! I'm a receptionist! G'fa ha ha!" Quote Ultros

Quote (SuperManBoy @ 23rd June 2004 22:15)

What did you mean about clearing the spot of the item you like?  Move the item in your equipment menu? You called it "the uneffected slot."

Well, an uneffected slot. Just find an item slot that wasn't tampered with by the bug (usually the first few and a lot of others from my experience) and move whatever you got to it. Sketch affects a lot of item slots, but not the majority, so you shouldn't have very many problems finding one. The best way to find one is to look up slots that already have items; if it looks familiar to you, the bug probably didn't tamper with it.

Quote (SuperManBoy @ 23rd June 2004 22:15)

Does mute being in the 28th magic spot have anything special to do with the glitch, or just a trigger?

It's aiming byte is special, but not the spell itself. 41h being at 7E:2100 can cause the Sketch bug. It doesn't have to be Mute if the game compresses your Magic list during battle and places something else there that has the same kind of aiming, but Mute is a great example because you can use it with a large or full Magic list to simplify things.

Quote (SuperManBoy @ 23rd June 2004 22:15)

And finally, when you get the items after, do they appear in the things you won, or you just have them?  I and everyone else thanks you again!!

If you couldn't tell from this post and the rest of the thread, you get the items once you execute the bug.


--------------------

The Unoriginal White Sheet

-Master ZED

Yeah, they're dropped immediately into your items list. So it's like "WHOA that's a lotta Illuminas there!"

--------------------

~Status Report~

* Completed... Dragon's Head
* Completed... Soldiers of the Empire: Disciples (release pending)
* In Progress/Undecided... Of Love and Betrayal
* Planning/Assembly... Where it all Began

Yeah! We can finally all have the Illumina (times infinity) and the Ragnorok esper!!!

This post has been edited by SuperManBoy on 24th June 2004 11:18

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"Look at me! I'm a receptionist! G'fa ha ha!" Quote Ultros

WOW... Zed you are truly impressive.

But would you consider using this to your advantage cheating?
I mean ahhh, multiple Illumina's?


--------------------

~*~*~*~*~*~*~*~
Midsummer dreamer,
Fantasy weaver,
Wild thing,
Noble king,
Spell caster,
Muggle Master
~*~*~*~*~*~*~*~

Quote (Muggle_Master @ 24th June 2004 08:22)

But would you consider using this to your advantage cheating?
I mean ahhh, multiple Illumina's?

Yeah, now that we're learning about how to safely use the bug, it could be considered a cheat. Not the worst in the game, mind you, but a cheat nonetheless.

--------------------

The Unoriginal White Sheet

-Master ZED

Well, it's dirty. But a cheat? It's using one of the game its flaws against it, that's all. I never considered the Vanish/Doom tactic a cheat either. I don't think there is such a thing as a 'cheat' in the game, there's just GameShark/etc. and save state hacking. It's not like you can press a specific button combo to instantly win a battle. It's like knowing how Slot works and pumping out Joker Doom spells every single battle just because you know how to do that.

This post has been edited by Djibriel on 24th June 2004 16:03

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The Collapse of Heaven and Earth

Good job discovering this flaw though!

--------------------

"Look at me! I'm a receptionist! G'fa ha ha!" Quote Ultros

Is anyone here besides Zed, going to test this one out?

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"When the clouds darken and things look their darkest, you just have to throw up your arms and say: OK, because it's probably going to get a helluva lot worse."

Thanks ZED for working that stuff out. I glitched my game (once on accident in the caves with the statues) and a few times on purpose (vanishing intangirs) and yeah it seems to work. Unfortunately i didn't have much of a method or my wits about me and saved right after i glitched it and i'm stuck with a relm in magitec armo who can't fight or sketch (no more glitching for me) as well as a terra who is unable to morph...also some of the sprites in and out of battle are changed (most look like they have a status effect but i've seen shadow a blueish green color and the top character in my battle sequences has a strange brownish color scheme to him...had i thought about it at the time i would have gotten a picture but i guess those aren't always acceptable verifications. Does anybody know of a hacking tool or patch that i can use to restore defaults in the game so that after you glitch it you can stabalize the characters again in their original form? cause i'd really like to get to use control in a bit and i forget if gogo can use it or not. On the bright side...i have enough exaliburs and aura lances to have shadow throw the rest of the game and not run out, a few hundred economizers, a large collection of fire shields, snow mufflers, sprint shoes, tinctures, a force shield, graedus, sky renders, etc., etc.
If i messed up the glitch and did it a different way then this might not be a relevant post, but at least then i'll know that i need to learn how to do it more safely.

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The more people i meet...the more i want to be a penguin

oh yeah...i also went ahead and finsihed the WOB im hoping that as i find characters in the WOR the glitched characters will return to normal (terra has to be able to morph when you get her in WOR if i remember correctly) and as for relm...im just keeping my fingerss crossed...on top of that i also lost both of my genji gloves (didn't steal any back from dragons) and the thief glove (changes steal to capture) so i guess thats just an extra warning for folks who want to glitch intentionally

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The more people i meet...the more i want to be a penguin

I had heard about Intangir's ill effects back in I think 1998 (think it was a secrets doc by Rabiteman), good to know it wasn't a pack of vicious lies, though that sucks that you're having to attempt to survive with the effects of that bug in place. The best I can do is link you to a save editor (FF3h) as that will probably be faster than PAR codes. As for the graphic glitches, I dunno what to tell ya. If you can't fix them in FF3h, maybe they'll repair themselves later, who can really say....

Gogo can use Control, and I might as well repeat this since you pointed it out; Sketch will overwrite items if the slots it affects have an item already there. However, the same variation of the bug will pretty much always affect the same slots, so you can prepare to use the bug by rearranging the list to make room for the new items. It may be a little painful to move all items out of the way, but at least you can save the valuable items.

As for Terra, you had better edit her to have Morph anyway. She'll be forced to have Morph in one battle, yes, but that's the status, not the command. You'll have to hack the command back in if you want to use it on your own.

--------------------

The Unoriginal White Sheet

-Master ZED

i never bothered much with the morph command...never lasted long enough for it to be effective for me so i'll probably keep relm out of my party and just plow on through...as far as intangirs being detrimental im glad that it was pointed out...do you think i would have a similiar problem with any other enemies? or could i vanish/sketch just about anyone else and not see these things?


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The more people i meet...the more i want to be a penguin

Must do that first one... must go all out Wind God... *drools*

--------------------

Uwao. aooh! I'm Gau!
I'm your friend!
Let's travel together!

I have a question. most of the time I go to the cave north of stragos villiage in the WOR (dont remember the name) and attempt to sketch the game crashes is there any way to avoid this besides not doing the sketch move?

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what is life without pain?

Quote (knave @ 30th June 2004 21:06)

I have a question.  most of the time I go to the cave north of stragos villiage in the WOR (dont remember the name)  and attempt to sketch the game crashes is there any way to avoid this besides not doing the sketch move?

Try using a different Magic Order. You have a spell there that has the 41h aiming scheme (think how Drain's cursor acts), take it out and you'll be safe from the bug.

And yes, a blank slot could still have the same aiming scheme (I'm not totally sure why, one idea is that the aiming byte is loaded with the MP cost regardless). However, if the character in the first slot has no Magic spells, you shouldn't encounter the Sketch bug. Since it sounds like you're on the Esper hunt, Strago would make a good lead to stop the bug due to his just now joining.

If that doesn't work, have whoever's in the first slot use Magic first, preferably an ailment or status spell (Vanish, etc.). That might effect the unknown byte, and if it does, you *should* be safe from the bug. The first character's unknown byte could be affected whenever it uses Magic though, so be careful if you continue to cast spells with that character.

--------------------

The Unoriginal White Sheet

-Master ZED

I could be wrong but his post says WOR so he would have had strago for a decent amout of time so using him might not work...
i'd says he's speaking of the cave where you fight hidon and get grand train

once again might be wrong...I'm sure Zed knows a bit more than i do about ff3

This post has been edited by notsolildrumrboy on 1st July 2004 12:26

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The more people i meet...the more i want to be a penguin

Well, I'm pretty sure that it's WoR Strago he's talking about, since WoB Tamasha doesn't even have a cave north of it. In which case I can recommend Umaro and Gogo as lead characters since they don't (necessarily) have the Magic Command.


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The Collapse of Heaven and Earth

i remember its called ebat rock (or something similar)


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what is life without pain?

alright...if you use djibriel's advice in conjunction with ZED's advice then it should clear up the problems


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The more people i meet...the more i want to be a penguin

I just had a thought: if the Sketch Bug can use targetting methods from spells that aren't even there, then maybe it can tap into Gogo's Magic even when he doesn't have it? That would make Umaro the only safe lead character for most people Luckily I hardly teach any spells to my characters.

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The Collapse of Heaven and Earth

Quote (Djibriel @ 1st July 2004 11:43)

I just had a thought: if the Sketch Bug can use targetting methods from spells that aren't even there, then maybe it can tap into Gogo's Magic even when he doesn't have it? That would make Umaro the only safe lead character for most people 

Actually, yes it does, but the Sketch bug appears to be a rare oddity, otherwise Sketch would have been a bigger problem and would have definitely appeared in FF6j (meaning we probably would never have seen it in the US). If you have a character that knows all spells and are on Magic Order 1, Gogo being on the same team as that person would make it just as safe to use though, as in the WOR (yeah, I wasn't paying attention yesterday), it's much less of a problem once you learn most, if not all, spells.

--------------------

The Unoriginal White Sheet

-Master ZED

*bows to Zed*

I am not worthy.

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Mercy?! I am the sixth phase of your world's destruction! would you like some evil pie?

My name is Fox, I am infinitely great, and I am the author of this comic strip..