Add a new fishing rod - pret/pokecrystal GitHub Wiki

This tutorial is for how to add a new fishing rod. As an example, we'll add a Master Rod, even better than a Super Rod.

Contents

  1. Create the new Rod item
  2. Define the item effect
  3. Define wild data for the new Rod
  4. Update the code that loads the wild data

1. Create the new Rod item

Follow the tutorial to add a new item to create the Master Rod. Replace ITEM_88 with MASTER_ROD, and give it a name, description, and attributes (0, HELD_NONE, 0, CANT_TOSS, KEY_ITEM, ITEMMENU_CLOSE, ITEMMENU_NOUSE). (ITEM_88 is not in TimeCapsule_CatchRateItems.)

2. Define the item effect

Edit engine/items/item_effects.asm:

 ItemEffects:
 ; entries correspond to item ids
 	dw PokeBallEffect      ; MASTER_BALL
 	...
 	dw NoEffect            ; ITEM_87
-	dw NoEffect            ; ITEM_88
+	dw MasterRodEffect     ; MASTER_ROD
 	dw NoEffect            ; ITEM_89
 	...
 	dw NoEffect            ; ITEM_B3

 ...

 OldRodEffect:
 	ld e, $0
 	jr UseRod

 GoodRodEffect:
 	ld e, $1
 	jr UseRod

 SuperRodEffect:
 	ld e, $2
 	jr UseRod
+
+MasterRodEffect:
+	ld e, $3
+	; fallthrough

 UseRod:
 	farcall FishFunction
 	ret

Pretty simple; we just observe how the other three Rods work, and follow their pattern. Since UseRod is right there underneath where we're editing, we can just fall through to it instead of jumping with jr; in fact, Game Freak could have done this themselves with SuperRodEffect.

3. Define wild data for the new Rod

Edit data/wild/fish.asm:

 time_group EQUS "0," ; use the nth TimeFishGroups entry

 fishgroup: MACRO
-; chance, old rod, good rod, super rod
-	dbwww \1, \2, \3, \4
+; chance, old rod, good rod, super rod, master rod
+	db \1
+	dw \2, \3, \4, \5
 ENDM

 FishGroups:
 ; entries correspond to FISHGROUP_* constants
-	fishgroup 50 percent + 1, .Shore_Old,            .Shore_Good,            .Shore_Super
-	...
-	fishgroup 50 percent + 1, .Qwilfish_NoSwarm_Old, .Qwilfish_NoSwarm_Good, .Qwilfish_NoSwarm_Super
+	fishgroup 50 percent + 1, .Shore_Old,            .Shore_Good,            .Shore_Super,            .Shore_Master
+	...
+	fishgroup 50 percent + 1, .Qwilfish_NoSwarm_Old, .Qwilfish_NoSwarm_Good, .Qwilfish_NoSwarm_Super, .Qwilfish_NoSwarm_Master

 ...

 .Remoraid_Old:
 	db  70 percent + 1, MAGIKARP,   10
 	db  85 percent + 1, MAGIKARP,   10
 	db 100 percent,     POLIWAG,    10
 .Remoraid_Good:
 	db  35 percent,     MAGIKARP,   20
 	db  70 percent,     POLIWAG,    20
 	db  90 percent + 1, POLIWAG,    20
 	db 100 percent,     time_group 6
 .Remoraid_Super:
 	db  40 percent,     POLIWAG,    40
 	db  70 percent,     time_group 7
 	db  90 percent + 1, MAGIKARP,   40
 	db 100 percent,     REMORAID,   40
+
+.Shore_Master:
+.Ocean_Master:
+.Lake_Master:
+.Pond_Master:
+.WhirlIslands_Master:
+	db  20 percent,     OMASTAR,    60
+	db  40 percent,     KABUTOPS,   60
+	db  70 percent,     OCTILLERY,  60
+	db  90 percent + 1, LAPRAS,     60
+	db 100 percent,     KINGDRA,    60
+
+.Gyarados_Master:
+	db  40 percent,     MAGIKARP,   60
+	db  70 percent,     GYARADOS,   60
+	db  90 percent + 1, GYARADOS,   60
+	db 100 percent,     GYARADOS,   60
+
+.Dratini_Master:
+.Dratini_2_Master:
+	db  40 percent,     GYARADOS,   60
+	db  70 percent,     KINGDRA,    60
+	db  90 percent + 1, DRAGONAIR,  60
+	db 100 percent,     DRAGONITE,  60
+
+.Qwilfish_Master:
+.Qwilfish_Swarm_Master:
+.Qwilfish_NoSwarm_Master:
+	db  40 percent,     TENTACRUEL, 60
+	db  70 percent,     QWILFISH,   60
+	db  90 percent + 1, QWILFISH,   60
+	db 100 percent,     QWILFISH,   60
+
+.Remoraid_Master:
+.Remoraid_Swarm_Master:
+	db  40 percent,     TENTACRUEL, 60
+	db  70 percent,     REMORAID,   60
+	db  90 percent + 1, REMORAID,   60
+	db 100 percent,     OCTILLERY,  60

Here we've modified the fishgroup macro to take four pointers instead of three; added new pointers to the end of each fishgroup line for the Master Rod; and declared the actual data for the new Master Rod pointers.

Notice the format of the wild data. Each line has the format "db chance, species, level" or "db chance, time_group index", with the chances increasing up to 100%. A random byte from 0% to 100% is generated, and compared with the chances to determine your encounter.

4. Update the code that loads the wild data

Edit constants/pokemon_data_constants.asm:

-FISHGROUP_DATA_LENGTH EQU 1 + 2 * 3
+FISHGROUP_DATA_LENGTH EQU 1 + 2 * 4

If you're using an older copy of pokecrystal and FISHGROUP_DATA_LENGTH does not exist, then edit engine/events/fish.asm instead:

 Fish:
 ; Using a fishing rod.
 ; Fish for monsters with rod e in encounter group d.
 ; Return monster e at level d.
 
 	push af
 	push bc
 	push hl
 
 	ld b, e
 	call GetFishGroupIndex
 
 	ld hl, FishGroups
-rept 7
+rept 9
 	add hl, de
 endr
 	call .Fish
 
 	pop hl
 	pop bc
 	pop af
 	ret

Either way, this allows the FishGroups table to be indexed by Rods from 0 to 3, instead of 0 to 2. (Remember how we defined MasterRodEffect.)

We're done!

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