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This starts a human-readable documentation of the various subsystems used in the game's map system. The following files are included in this commit: - `maps.md`: a general overview of maps - `bdhc.md`: an overview of the BDHC subsystem, which is used to provide height information on maps - `loading_maps.md`: an overview of how maps are loaded by the game - `file_format_specifications.md`: specs for the maps data structures The `file_format_specifications.md` is meant to be a purely technical document that contains a precise description of the data structures used by the game's map system. The other files are meant to be semi-technical documentation, where some of the nitty-gritty details have been either simplified or left out entirely. Some of the maps subsystems were purposefully left out of this commit, such as map objects and map scripts. They will need to be addressed in future updates to those documents. Signed-off-by: Kuruyia <github@kuruyia.net>
160 lines
8.2 KiB
Markdown
160 lines
8.2 KiB
Markdown
# Maps
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This document aims to provide an overview of how the playground is constructed,
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excluding BDHC, which is covered in [its own document](bdhc.md).
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## Introduction
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Maps are the main building block of the playground. They are defined by various
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properties, which are explored throughout this document.
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Maps in Pokémon Platinum are a bit of a hybrid between 2D and 3D: they retain a
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2D grid system that was used in previous games, on which the terrain attributes
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dictate the collision and behavior of each tile, and on which map objects (such
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as the player) are constrained.
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They also have 3D elements, such as the map model which is used to render the
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map, and the BDHC subsystem which is used to add height and height variations
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to the terrain.
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Basically, from the 2D perspective, we can consider that a map is a grid of 32x32
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tiles. From the 3D perspective, we can consider that a map is a grid of 512x512 units,
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where each unit is 1/16th of a tile, and where the height at any point is given
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by one or more BDHC plates.
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## Map
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### Map header
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The map header is a structure that contains metadata about a map. It is the
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starting point of loading maps, and is what is stored in the save data to keep
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track of the player's position, alongside their X and Z coordinates.
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The map header contains various identifiers to other data structures:
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- the area data to load
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- the map matrix in which the map is located
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- the scripts and initialization scripts of the map
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- the text bank that contains the messages of the map
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- the music to play during day and night
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- the wild encounters data
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- the events data
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- the map name
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- the background used when displaying the map name
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It also directly contains various properties:
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- the weather
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- the camera type
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- the type of map
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- the background used during battles
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- whether cycling is allowed
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- whether running is allowed
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- whether the escape rope can be used
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- whether fly can be used
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### Map data
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Stored in another archive inside the ROM, the map data contains the bulk of
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what's needed to render a map and have a player interact with it.
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The map data contains the following:
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- attributes for each tile of the map, which dictates whether a tile can be
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walked on (collision data), and how the tile behaves when interacted with:
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is it tall grass, water, a trash can, etc.
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- the base 3D model of the map, which is stored inside an NSBMD container
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- the BDHC data
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| Everything rendered | Map model only |
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| ---------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
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Above is an image of Jubilife City with only the map model (which means, without
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the map objects and map props) to get a good grasp at what the base map contains.
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Stored inside the map data is also the instances of the map props placed on the map,
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having the following properties:
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- the identifier to the 3D model of the map prop
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- its position on the map
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- its rotation on the map
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- the scale at which it should be rendered
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| Everything rendered | Map props only |
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| ---------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- |
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## Map matrix
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Map matrices are the game's way of organizing maps in a grid. They are used to
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create a coherent world, where maps are connected to each other, and where the
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player can seamlessly move from one map to another.
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There exist multiple map matrices in the game, the two biggest ones being the
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overworld map matrix (being 30x30 maps) and the underground map matrix (being
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15x15 maps). However, the vast majority of map matrices do not exceed 2x2 maps,
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and are used for small, interior areas such as buildings or caves.
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Map matrices contain the following properties:
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- a height and a width (in maps)
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- the IDs of the map headers of each map in the matrix
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- the IDs of the map data of each map in the matrix
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- altitudes for each map, which affects the height at which the map and its
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props are rendered
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## Area
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Areas are basically a middle ground between maps and map matrices. They are used
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to group maps together, and a map matrix can have multiple areas. On the contrary,
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a map can only belong to one area.
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Here are the areas of the overworld map matrix:
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If you checked what's present in the border between two areas, you'd see that there is
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a gate, a cave, or any other kind of warp. This illustrates how gates are used to force
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a warp, which allows the game to load a different set of resources (but a warp doesn't
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necessarily mean a change of area).
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Areas regroup rendering resources common to multiple maps, and that are loaded
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when entering a map in the area. This includes:
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- the 3D models of the map props
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- the textures of the map props
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- the animation data of the map props
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- the textures of the map models
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- the lighting configuration, described below
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### Lighting
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Lighting data is actually dictated by area rather than map. This data is intimately
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linked to the Nintendo DS 3D hardware, and directly maps to its capabilities.
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The Nintendo DS supports 4 different lights, each with their own direction vector
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and color, and those lights can be toggled on and off to only affect certain polygons.
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In game, this translates to the following usage:
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| Light # | Screenshot | Used on (non-exhaustive) |
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| ------- | ---------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------- |
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| Light 0 |  | 2D sprites, base 3D model of the map, most of the polygons of map props |
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| Light 1 | N/A | Seemingly unused |
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| Light 2 |  | Building windows |
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| Light 3 |  | Lamp post lights, building lights and doors (only glass doors: PokéCenter, PokéMart, Gyms...) |
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In the above screenshots, the corresponding lights are in red.
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The game supports 4 different "lighting configurations":
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- the first one is used by outside areas
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- the second one is used by inside areas
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- the third one is used by some specific areas (Lost Tower, Mount Coronet and
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Iron Island)
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- the fourth one is seemingly unused
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Those lighting configurations are also affected by the current wall time, which
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allows the game to change lighting depending on the time of the day.
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