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Generation II Glitch Discussion

Brn/Psn/Par dont affect catch rate in GSC - Page 1

Brn/Psn/Par dont affect catch rate in GSC

Posted by: Bent`
Date: 2012-05-18 00:48:28
In RBY, Sleep and Freeze provide a higher catch rate than Burn/Poison/Paralysis, which in turn provide a higher catch rate than no status effect at all.

They tried to do the same in GSC, but introduced a bug that makes Burn/Poison/Paralysis provide the same catch rate as no status effect.

The GSC catch rate formula is explained here.

D = wild Pokémon's status: if asleep or frozen, D=10; if burned, paralyzed, or poisoned, D=5; else D=0

That is what the code attempts to do. The code looks like this:

        ld b, a
        ld a, [WildPokemonStatus]
        and SLP|FRZ
        ld c, 10
        jr nz, .done
        and a
        ld c, 5
        jr nz, .done
        ld c, 0
.done

and a is a quick zero check, but here it will always evaluate to 0, because nonzero values are caught by the jr immediately preceding it. As a result, the second jr never gets followed, and the modifier is always set to zero.

Here is a modified version of the routine that works properly:

        ld b, a
        ld a, [WildPokemonStatus]
        and a
        ld c, 0
        jr z, .done
        and SLP|FRZ
        ld c, 10
        jr nz, .done
        ld c, 5
.done

Re: Brn/Psn/Par dont affect catch rate in GSC

Posted by: Kyoukipichi
Date: 2012-05-18 17:39:02
Quite frankly, this was an unnoticeable bug, so I'm not really that surprised that it stayed in all this time.

Shame, though.

Re: Brn/Psn/Par dont affect catch rate in GSC

Posted by: GARYM9
Date: 2012-05-20 00:07:51
Placebo effect.

Re: Brn/Psn/Par dont affect catch rate in GSC

Posted by: Halfshadow
Date: 2016-04-11 08:51:35
Sorry if I up but i Think is important.

Are you sure IImarkus that the code is correct? If I change the asm instructions with your, decrease the catch rate of the pokémon in full health. Rattata and other pokémons of the Route 1 become almost impossible to catch with a MEGA BALL in full heal, a PIDGEY have lost all it's PP 'cause the balls haven't catched it.

You have wrote that the right code will be this:


        ld b, a
        ld a, [WildPokemonStatus]
        and a
        ld c, 0
        jr z, .done
        and SLP|FRZ
        ld c, 10
        jr nz, .done
        ld c, 5
.done

But the catch rate of a full health pokémon back normal if I tipe this instead:


        ld b, a
        ld a, [WildPokemonStatus]
        and a
        ld c, 0
        jr nz, .done
        and SLP|FRZ
        ld c, 10
        jr nz, .done
        ld c, 5
.done

Have you mistaked something when you tiped the code?

Re: Brn/Psn/Par dont affect catch rate in GSC

Posted by: Bent`
Date: 2016-04-20 21:48:59

Sorry if I up but i Think is important.

Are you sure IImarkus that the code is correct? If I change the asm instructions with your, decrease the catch rate of the pokémon in full health. Rattata and other pokémons of the Route 1 become almost impossible to catch with a MEGA BALL in full heal, a PIDGEY have lost all it's PP 'cause the balls haven't catched it.


It works fine when I try it (Ultra Ball catches level 23 Pokémon easily in 13 tries, whether paralyzed or not). Im guessing you made some sort of mistake when modifying the code.

Re: Brn/Psn/Par dont affect catch rate in GSC

Posted by: Halfshadow
Date: 2016-04-22 11:26:56
Have you tried also with the MEGA (GREAT) BALL? I've tried with it before and after the fix and was different.