Change Boss Drops?

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Change Boss Drops?

Post by LeviKornelsen on Sun 26 Aug 2018 - 23:13

So, just getting into hacking at LttP, my concept for a "This should be an easy entry into hacking the game" concept was "Heartbreak", which would do the following:

1. Give the player some added starting gear - nothing huge, boomerang, boots, whatever.  No problem; figured out how that works with Hyrule Magic.

2. Add pieces of heart to the places where the new starting gear used to be.  This also looks doable with Hyrule Magic.

3. Change heart container drops and placements into pieces of heart instead.  All bosses, chest at sanctuary, all of 'em.

4. Maybe scatter some more pieces around the map.

...Number three is where I'm sitting, going, uhhh...   Hex hacking?  Yikes!

Is that what'd be required to change boss drops?

...

EDIT: Crap, probably wrong sub-forum.

LeviKornelsen
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Re: Change Boss Drops?

Post by Conn on Mon 27 Aug 2018 - 5:05

Without wanting to trace it, check:
https://www.zeldix.net/t1635-wizzrobemaster-s-burning-questions

If I get Puzz's notes correctly, you need to change
0x4ee50: ea -> eb
0x2A079: ea -> eb (armos special?)
(open the rom in a hex editor, press Ctrl+g and search the address, and then change that byte)

But you may want to wait for puzz to confirm.
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Conn



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Re: Change Boss Drops?

Post by LeviKornelsen on Mon 27 Aug 2018 - 5:43

Reading over that thread, it looks like something of that nature is what's called for, yeah; time to dig into hex editing.

If Puzzledude is in the mood to clarify / has cracked this since / etc, I'd be quite happy to hear about it, but I think that thread has enough pointers to start digging into the thing myself either way. Thanks.

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Re: Change Boss Drops?

Post by Puzzledude on Mon 27 Aug 2018 - 12:32

1. Give the player some added starting gear - nothing huge, boomerang, boots, whatever. No problem; figured out how that works with Hyrule Magic.
This is easy doable either by giving this in chests or even easier, by hacking in the starting gear, which is in the Rom itself (and all usually set to 0), and then gets writen into RAM and then SRAM. I decoded this a while back for all items, so...

2. Add pieces of heart to the places where the new starting gear used to be. This also looks doable with Hyrule Magic.
4. Maybe scatter some more pieces around the map.
Easy doable by changing the chest content to pieces of heart.

3. Change heart container drops and placements into pieces of heart instead. All bosses, chest at sanctuary, all of 'em.
...Number three is where I'm sitting, going, uhhh... Hex hacking? Yikes! Is that what'd be required to change boss drops?
This is not so easy. Boss drops are a pain to change and would require ASM and HEX, and even then the game is confused. You can easily change the drop of a boss itself, but then! the game will not drop the pendant or crystal - you'd be permanently stuck and could not finish the game at all. The game only knows to drop the pendant or crystal, if you pick up a heart container.

However for a boss to drop heart pieces instead was indeed decoded by Reshaper:

02A079: from EA to EB
=Armos drops heart piece instead of container

02A538: from EA to EB
=Lanmolas drop heart piece instead of container

04EE50: from EA to EB
=all other bosses remaining drop heart piece instead of container

You can change the EB sprite to any other sprite, like DA, then the boss will drop 5 rupees, but like said, no pendant/crystal drop will occur then.

But for heart piece Reshaper found the byte to then still drop treasure (only works for heartpieces no other custom sprite drop):
02F006: from 40 20 to C0 A0
= this will set the high bit in RAM $0403, which is necessary to still drop pendant/crystal if heart piece from boss.

044A99: from AD to EA,
this is only necessary as debug, since the former edit at 02F006 might conflict with this code, so the command AD is NOPed out.


Also do note that if you do this, then:
-the heartpiece will jump much higher in the air than it should when it spawns (and there is nothing you can do to fix this)

-the delay between obtaining the heartpiece from boss and the pendatn/crystal drop will now be longer

-the heartpiece will not have the shallow water effect when Arghus is defeated (and there is nothing you can do to fix this)

-if you collect the fourth heartpiece and thus go into the hold the entire heartpiece in the air mode, the GFX of the pendant/crystal will be glitched-looking (and there is nothing you can do to fix this)

You can clearly see, that the game was made to drop heart containers and this is somehow fixed. Any hacking of this sequence will produce problems and chain events.
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Re: Change Boss Drops?

Post by LeviKornelsen on Mon 27 Aug 2018 - 13:19

Those are some... interesting side effects, for sure.

Will certainly test it out to see the length of delay and badness of the glitch, but I suspect I'll need to find a "starter project" that doesn't weird the look of things and come back to this concept with a touch more experience in the "can I make it worth it?" department.

Thanks, folks.

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