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diff --git a/Maps-that-require-Flash.md b/Maps-that-require-Flash.md new file mode 100644 index 0000000..08ce937 --- /dev/null +++ b/Maps-that-require-Flash.md @@ -0,0 +1,216 @@ +This tutorial is for how to edit which maps require FLASH to see in. +## Contents +- [Location of original code](#location-of-original-code) +- [0. Understanding the code setup for what needs FLASH](#0-understanding-the-code-setup-for-what-needs-flash) +- [1. Prepping the code for additions](#1-prepping-the-code-for-additions) +- [2. Implementing a map](#2-implementing-a-map) +- [3. Code cleanup](#3-code-cleanup) + +## Location of original code + +The location of where this is found is in home/overworld.asm. +Credit goes to wrulfy on the pret Discord server for finding it. + +Specifically it is under the WarpFound2:: section + +Original code: +```diff +WarpFound2:: + ld a, [wNumberOfWarps] + sub c + ld [wWarpedFromWhichWarp], a ; save ID of used warp + ld a, [wCurMap] + ld [wWarpedFromWhichMap], a + call CheckIfInOutsideMap + jr nz, .indoorMaps +; this is for handling "outside" maps that can't have the 0xFF destination map + ld a, [wCurMap] + ld [wLastMap], a + ld a, [wCurMapWidth] + ld [wUnusedD366], a ; not read + ldh a, [hWarpDestinationMap] + ld [wCurMap], a + cp ROCK_TUNNEL_1F + jr nz, .notRockTunnel + ld a, $06 + ld [wMapPalOffset], a + call GBFadeOutToBlack +.notRockTunnel + call PlayMapChangeSound + jr .done +``` + + +## 0. Understanding the code setup for what needs FLASH + +What matters to us are the few lines at and after "cp ROCK_TUNNEL_1F" which are shown here below for simplification. +```diff + cp ROCK_TUNNEL_1F + jr nz, .notRockTunnel + ld a, $06 + ld [wMapPalOffset], a + call GBFadeOutToBlack +.notRockTunnel + call PlayMapChangeSound + jr .done +``` + +Now to understand, I'm going to separate it up even more. + +When entering a new map, this line checks if the new map is ROCK_TUNNEL_1F or more simply maps\RockTunnel1F.blk +```diff + cp ROCK_TUNNEL_1F +``` + +The next line gives a divergent destination based on if yes/no. +"jr" means "Jump to close location". +"nz" means "If equals zero", or in other words, "If not RockTunnel", since that is what we checked for. +It translates to "If not ROCK_TUNNEL_1F, then go to the sub-section ".notRockTunnel" +```diff + jr nz, .notRockTunnel +``` + +If it is sent to the sub-section ".notRockTunnel", then it jumps (jr) here. +```diff +.notRockTunnel +``` + +Based on if .notRockTunnel or ROCK_TUNNEL_1F, will load 2 separate states. +Below is if it is a normal (no FLASH needed) map. +Nothing fancy, just loads the new map normally. +```diff + call PlayMapChangeSound +``` + +This is if it is meant to load a FLASH-required map. It is what sets up "needs FLASH to see". +```diff + ld a, $06 + ld [wMapPalOffset], a + call GBFadeOutToBlack +``` +This is the termination of the entire action. +```diff + jr .done +``` + + + +## 1. Prepping the code for additions + +The problem with the original code is how it treats the default and the exception. +Due to the exception being .notRockTunnel, that means the default is Rock Tunnel. Which is fine for only have a single FLASH-required location. But we want more than just that. + +So first we are going to change the code to treat the default state as normal, and the exception to the rule as "needing FLASH". + +The base step is to change the "if, then jump" line. +What this will do is instead of a "not, then jump" we'll have a "yes, then jump" action. +```diff +- jr nz, .notRockTunnel ++ jr n, .yesRockTunnel +``` + +Then we need to rename the jumped to location. +```diff +-.notRockTunnel ++.yesRockTunnel +``` + +Next we need to swap what is loaded via the default and the exception. + +Default state: +```diff +- ld a, $06 +- ld [wMapPalOffset], a +- call GBFadeOutToBlack ++ call PlayMapChangeSound +``` + +Exception state: +```diff +- call PlayMapChangeSound ++ ld a, $06 ++ ld [wMapPalOffset], a ++ call GBFadeOutToBlack +``` + +So what the entire section we changed should look like is the following: +```diff + cp ROCK_TUNNEL_1F +- jr nz, .notRockTunnel ; Old ; If no, then jump to exception ++ jr n, .yesRockTunnel ; New ; If yes, then jump to exception. +- ld a, $06 ; Old Normal ; needs FLASH +- ld [wMapPalOffset], a ; Old Normal ; needs FLASH +- call GBFadeOutToBlack ; Old Normal ; needs FLASH ++ call PlayMapChangeSound ; New Normal ; no FLASH needed +-.notRockTunnel ++.yesRockTunnel +- call PlayMapChangeSound ; Old Exception ; no FLASH needed ++ ld a, $06 ; New Exception ; needs FLASH ++ ld [wMapPalOffset], a ; New Exception ; needs FLASH ++ call GBFadeOutToBlack ; New Exception ; needs FLASH + jr .done +``` + +Having made this change will have no discernible effect in game thus far. +But we'll have prepped the code for easy addition of other maps to require FLASH. + + +## 2. Implementing a map + +This is the easiest part. +All we have to do is add in a new "check & jump" to the section. + +For example, if I wanted to make the Power Plant require FLASH then I would need to create and insert the following. +```diff + cp POWER_PLANT ; Checks if POWER_PLANT + jr n, .yesPowerPlant ; If yes, then jump to .yesPowerPlant +.yesPowerPlant + ld a, $06 ; New Exception ; needs FLASH + ld [wMapPalOffset], a ; New Exception ; needs FLASH + call GBFadeOutToBlack ; New Exception ; needs FLASH +``` + +We just have to insert the check after the Rock Tunnel check and the jump location after the .yesRockTunnel location. + +So the end result would be as follows: +```diff + cp ROCK_TUNNEL_1F + jr n, .yesRockTunnel ; New ; If yes, then jump to exception. ++ cp POWER_PLANT ; Checks if POWER_PLANT ++ jr n, .yesPowerPlant ; If yes, then jump to .yesPowerPlant + call PlayMapChangeSound ; New Normal ; no FLASH needed +.yesRockTunnel + ld a, $06 ; New Exception ; needs FLASH + ld [wMapPalOffset], a ; New Exception ; needs FLASH + call GBFadeOutToBlack ; New Exception ; needs FLASH ++.yesPowerPlant ++ ld a, $06 ; New Exception ; needs FLASH ++ ld [wMapPalOffset], a ; New Exception ; needs FLASH ++ call GBFadeOutToBlack ; New Exception ; needs FLASH + jr .done +``` + + +## 3. Code cleanup + +If you plan on adding a significant number of locations, changing a bit might be best to have a cleaner code. Renaming the exception for ease. +```diff + cp ROCK_TUNNEL_1F ; Checks if ROCK_TUNNEL_1F +- jr nz, .notRockTunnel ++ jr n, .yesFlashNeeded ; New exception name & condition ++ cp POWER_PLANT ; Checks if POWER_PLANT ++ jr n, .yesFlashNeeded ; New exception name & condition +- ld a, $06 +- ld [wMapPalOffset], a +- call GBFadeOutToBlack ++ call PlayMapChangeSound ; New Normal ; no FLASH needed +-.notRockTunnel ++.yesFlashNeeded +- call PlayMapChangeSound ++ ld a, $06 ; New Exception ; needs FLASH ++ ld [wMapPalOffset], a ; New Exception ; needs FLASH ++ call GBFadeOutToBlack ; New Exception ; needs FLASH + jr .done + + +Add as many location as you want, with the requirement being, it must be entered from the Overworld.
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