Need help with a Pokemon Emerald Mod Idea

[FireLordZuko]

Hi everyone,

I'm interested in a mod of Pokemon Emerald where a certain battle mechanic is changed. Don't need to change any storyline plots, maps, pokemon, characters, move etc. Only thing that needs to change is this one mechanic.

I'm looking at having a random weather effect activated in every battle. Don't need the overworld to change, just this mechanic.

Can anyone point me in the right direction of the tool that's best used to change a battle mechanic?

 

[Anon822]

Hi everyone,

I'm interested in a mod of Pokemon Emerald where a certain battle mechanic is changed. Don't need to change any storyline plots, maps, pokemon, characters, move etc. Only thing that needs to change is this one mechanic.

I'm looking at having a random weather effect activated in every battle. Don't need the overworld to change, just this mechanic.

Can anyone point me in the right direction of the tool that's best used to change a battle mechanic?

Since you're posting this in the decomp section I'm guessing that you already know that the pokeemerald decomp is the best tool for changing or creating game mechanics, as it makes editing the game's code easy. With the decomp you can create a mod like that just by using any text editor program.

To be able to write code that makes a random weather effect activate at the start of battle, you would need to know how to start weather in battle, and where you should add your code to have it run at the start of the battle. Luckily the game already has logic for setting battle weather based on the overworld weather, so you can just modify that to start a random weather instead.

 

[Bivurnum]

Hi everyone,

I'm interested in a mod of Pokemon Emerald where a certain battle mechanic is changed. Don't need to change any storyline plots, maps, pokemon, characters, move etc. Only thing that needs to change is this one mechanic.

I'm looking at having a random weather effect activated in every battle. Don't need the overworld to change, just this mechanic.

Can anyone point me in the right direction of the tool that's best used to change a battle mechanic?

I thought this would be a fun idea to practice my coding on, so I took a stab at it and got it to work! Here's what I did:

Spoiler:

In src/battle_util.c here (at line 2473) add the following right before the if statement:

                    if (!FlagGet(FLAG_DO_NORMAL_WEATHER))
                    {
                        u16 random = Random();
                        int randweather = (random % 199); //sets a random number between 0 and 199

                        if(randweather < 50)
                        {
                            gWeatherPtr->currWeather = WEATHER_DOWNPOUR;
                        }
                        else if(randweather < 100)
                        {
                            gWeatherPtr->currWeather = WEATHER_DROUGHT;
                        }
                        else if(randweather < 150)
                        {
                            gWeatherPtr->currWeather = WEATHER_SANDSTORM;
                        }
                        else
                        {
                            gWeatherPtr->currWeather = WEATHER_SNOW;
                        }
                    }

Then, still in battle_util.c, add the following code here (the new line will be 2529) immediately after the break:

                    case WEATHER_SNOW: //adds the ability for battles to start with hail active
                        gBattleWeather = B_WEATHER_HAIL;
                        gBattleScripting.animArg1 = B_ANIM_HAIL_CONTINUES;
                        gBattleScripting.battler = battler;
                        effect++;
                        break;

In src/battle_message.c, add the following code here (at line 481) right after the sandstorm line:

static const u8 sText_ItIsHailing[] = _("Hail is falling down.");

You can change what is inside the quotes to whatever you want it to say when a battle starts with hail. You don't have to keep the wording I used. Up to you.

In that same file, add the following code here (the new line will be 782) after the line for sandstorm:

[STRINGID_ITISHAILING - BATTLESTRINGS_TABLE_START] = sText_ItIsHailing,

Still in battle_message.c, REPLACE the line here (the new line will be 1164) with this:

[WEATHER_SNOW]               = STRINGID_ITISHAILING,

In include/constants/battle_string_ids.h, add the following here (at line 381) after STRINGID_TRAINER2WINTEXT:

#define STRINGID_ITISHAILING                381

Make sure to change the value of BATTLESTRINGS_COUNT (right after the line you just added) to 382.

Lastly, in include/constants/flags.h, REPLACE the line here (line 1220) with the following (this can replace one of the other unused flags instead, if you prefer):

#define FLAG_DO_NORMAL_WEATHER                                      0x493 // Disables random weather in battle

Save all of the files and run a make command. You now have a ROM of Pokemon Emerald that has a random weather effect in every battle!

I tied this mechanic to the flag FLAG_DO_NORMAL_WEATHER. Therefore, if you wanted to turn it off and back on again with scripts, it is as easy as using setflag or clearflag as needed. But I set it up so the random weather happens by default, in case you don't want to do anything with scripting.

I get the feeling that you've never dealt with decomps before, so if you want to get to the point where you can follow my above instructions, click this link and follow the steps to install pokeemerald. Once it is installed, it is really easy to change whatever code you want. You'll just need a text editor. Personally, I use Visual Studio Code, but you can use whatever you want in order to edit the code files. If you're interested, a great map editor for pokeemerald is Porymap. If you're looking for basic tutorials, I'd recommend checking out the tutorial videos on the Team Aqua's Hideout YouTube channel.

I know this can seem like a lot to a beginner, so if you have any questions along the way, feel free to ask!

(Edited for ease of use and fixed an error)

 

[Anon822]

I thought this would be a fun idea to practice my coding on, so I took a stab at it and got it to work! Here's what I did:

Spoiler:

In src/battle_util.c at line 2473 (in AbilityBattleEffects) add the following:

                    if (!FlagGet(FLAG_DO_NORMAL_WEATHER))
                    {
                        u16 random = Random();
                        int randweather = (random % 199); //sets a random number between 0 and 199

                        if(randweather < 50)
                        {
                            gWeatherPtr->currWeather = WEATHER_DOWNPOUR;
                        }
                        else if(randweather < 100)
                        {
                            gWeatherPtr->currWeather = WEATHER_DROUGHT;
                        }
                        else if(randweather < 150)
                        {
                            gWeatherPtr->currWeather = WEATHER_SANDSTORM;
                        }
                        else
                        {
                            gWeatherPtr->currWeather = WEATHER_SNOW;
                        }
                    }

Then, still in battle_util.c, add the following code at line 2529:

                    case WEATHER_SNOW: //adds the ability for battles to start with hail active
                        gBattleWeather = B_WEATHER_HAIL;
                        gBattleScripting.animArg1 = B_ANIM_HAIL_CONTINUES;
                        gBattleScripting.battler = battler;
                        effect++;
                        break;

In src/battle_message.c, add the following code at line 481:

static const u8 sText_ItIsHailing[] = _("Hail is falling down.");

You can change what is inside the quotes to whatever you want it to say when a battle starts with hail. You don't have to keep the wording I used. Up to you.

In that same file, add the following code at line 782:

[STRINGID_ITISHAILING - BATTLESTRINGS_TABLE_START] = sText_ItIsHailing,

Still in battle_message.c, REPLACE line 1164 with this:

[WEATHER_SNOW]               = STRINGID_ITISHAILING,

In include/constants/battle_string_ids.h, add the following at line 381:

#define STRINGID_ITISHAILING                381

Make sure to change the value of BATTLESTRINGS_COUNT (right after the line you just added) to 382.

Lastly, in include/constants/flags.h, REPLACE line 1221 with the following (this can replace one of the other unused flags instead, if you prefer):

#define FLAG_DO_NORMAL_WEATHER                                      0x493 // Disables random weather in battle

Save all of the files and run a make command. You now have a ROM of Pokemon Emerald that has a random weather effect in every battle!

I tied this mechanic to the flag FLAG_DO_NORMAL_WEATHER. Therefore, if you wanted to turn it off and back on again with scripts, it is as easy as using setflag or clearflag as needed. But I set it up so the random weather happens by default, in case you don't want to do anything with scripting.

I get the feeling that you've never dealt with decomps before, so if you want to get to the point where you can follow my above instructions, click this link and follow the steps to install pokeemerald. Once it is installed, it is really easy to change whatever code you want. You'll just need a text editor. Personally, I use Visual Studio Code, but you can use whatever you want in order to edit the code files. If you're interested, a great map editor for pokeemerald is Porymap. If you're looking for basic tutorials, I'd recommend checking out the tutorial videos on the Team Aqua's Hideout YouTube channel.

I know this can seem like a lot to a beginner, so if you have any questions along the way, feel free to ask!

Nice work! But using just line numbers to express locations is bad. As the decomp gets updated those numbers can change, so you should at least specify what commit those line numbers are for.

 

[Bivurnum]

Nice work! But using just line numbers to express locations is bad. As the decomp gets updated those numbers can change, so you should at least specify what commit those line numbers are for.

I agree the way I did it was kind of bad. I'd like my code changes to be displayed with a little bit of the surrounding code to give more of a reference for location and context. However, text color doesn't work properly inside the code box, and without a way to differentiate what is changed code and what isn't, I felt it would be too confusing for people to follow easily.

Just so I understand, when you say to specify the commit do you mean using a link like this? Therefore, an example of my code instruction would look something like this, correct?:

Spoiler:

In src/battle_util.c at line 2473 (in AbilityBattleEffects) add the following:

                    if (!FlagGet(FLAG_DO_NORMAL_WEATHER))
                    {
                        u16 random = Random();
                        int randweather = (random % 199); //sets a random number between 0 and 199

                        if(randweather < 50)
                        {
                            gWeatherPtr->currWeather = WEATHER_DOWNPOUR;
                        }
                        else if(randweather < 100)
                        {
                            gWeatherPtr->currWeather = WEATHER_DROUGHT;
                        }
                        else if(randweather < 150)
                        {
                            gWeatherPtr->currWeather = WEATHER_SANDSTORM;
                        }
                        else
                        {
                            gWeatherPtr->currWeather = WEATHER_SNOW;
                        }
                    }

 

[Anon822]

Just so I understand, when you say to specify the commit do you mean using a link like this? Therefore, an example of my code instruction would look something like this, correct?:

Yes, that's one way to do it. The part after "blob" in the link is the commit id, so the link always leads to that specific version of the decomp.

If you want to show surrounding code and what was changed you can display your changes as diffs, but the + symbols make copy-pasting larger code blocks less convenient.

Spoiler:

--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -2471,6 +2471,28 @@ u8 AbilityBattleEffects(u8 caseID, u8 battler, u8 ability, u8 special, u16 moveA
             switch (gLastUsedAbility)
             {
             case ABILITYEFFECT_SWITCH_IN_WEATHER:
+           if (!FlagGet(FLAG_DO_NORMAL_WEATHER))
+           {
+               u16 random = Random();
+               int randweather = (random % 199); //sets a random number between 0 and 199
+
+               if(randweather < 50)
+               {
+                   gWeatherPtr->currWeather = WEATHER_DOWNPOUR;
+               }
+               else if(randweather < 100)
+               {
+                   gWeatherPtr->currWeather = WEATHER_DROUGHT;
+               }
+               else if(randweather < 150)
+               {
+                   gWeatherPtr->currWeather = WEATHER_SANDSTORM;
+               }
+               else
+               {
+                   gWeatherPtr->currWeather = WEATHER_SNOW;
+               }
+           }
                 if (!(gBattleTypeFlags & BATTLE_TYPE_RECORDED))
                 {
                     switch (GetCurrentWeather())

 

[Bivurnum]

Yes, that's one way to do it. The part after "blob" in the link is the commit id, so the link always leads to that specific version of the decomp.

If you want to show surrounding code and what was changed you can display your changes as diffs, but the + symbols make copy-pasting larger code blocks less convenient.

Spoiler:

--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -2471,6 +2471,28 @@ u8 AbilityBattleEffects(u8 caseID, u8 battler, u8 ability, u8 special, u16 moveA
             switch (gLastUsedAbility)
             {
             case ABILITYEFFECT_SWITCH_IN_WEATHER:
+           if (!FlagGet(FLAG_DO_NORMAL_WEATHER))
+           {
+               u16 random = Random();
+               int randweather = (random % 199); //sets a random number between 0 and 199
+
+               if(randweather < 50)
+               {
+                   gWeatherPtr->currWeather = WEATHER_DOWNPOUR;
+               }
+               else if(randweather < 100)
+               {
+                   gWeatherPtr->currWeather = WEATHER_DROUGHT;
+               }
+               else if(randweather < 150)
+               {
+                   gWeatherPtr->currWeather = WEATHER_SANDSTORM;
+               }
+               else
+               {
+                   gWeatherPtr->currWeather = WEATHER_SNOW;
+               }
+           }
                 if (!(gBattleTypeFlags & BATTLE_TYPE_RECORDED))
                 {
                     switch (GetCurrentWeather())

Thank you! You've been very helpful. I'll edit the original reply to be more future proof.