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The Kirby's Epic Yarn level format is separated into two parts: mapbin (for level contents, excluding enemies) and enbin (for exclusively enemies).

Common structures

Vec2f:

struct Vec2f {
	float x;
	float y;
};

Vec3f:

struct Vec3f {
	float x;
	float y;
	float z;
};

String32,String64:

using String32 = char[32];
using String64 = char[64];

CountOffsetPair:

struct CountOffsetPair {
	u32 count;
	u32 offset; // relative to the start of the file
};

MapdataParams:

struct MapdataParams {
	int intParams[3];
	float floatParams[3];
	String64 stringParams[3];
}; // size = 0xD8

CommonGimmickParams:

struct CommonGimmickParams {
	int commonIntParams[2];
	float commonFloatParams[2];
	char commonStringParam[8];
	int intParams[5];
	float floatParams[5];
	String64 stringParams[5];
}; // size = 0x178

Mapbin

General Information

Byte order: big-endian
Sections: 11
- header
- walls
- labeled walls
- gimmicks
- common gimmicks
- paths
- zones
- (race) course info
- common gimmick name bank
- collision type name bank
- wall label name bank

This format does not have padding in-between sections. The file is padded with a value of 0 to a size that is a multiple of 0x20.

Format Documentation

Size = 0x58

field	offset	size	data type	description
unknown	`0x0`	`0x4`	`float`	This value is often seen to be ~`3.3f`. Values lower than this seem to crash the game.
minimum camera position	`0x4`	`0x8`	`Vec2f`	The camera position will not go lower than this.
maximum camera position	`0xC`	`0x8`	`Vec2f`	The camera position will not go higher than this.
walls	`0x14`	`0x8`	`CountOffsetPair`	Terrain collision.
labeled walls	`0x1C`	`0x8`	`CountOffsetPair`	Terrain collision with labels for additional processing.
common gimmicks	`0x24`	`0x8`	`CountOffsetPair`	Level entities that are frequently used.
gimmicks	`0x2C`	`0x8`	`CountOffsetPair`	Level entities that are less frequently used.
paths	`0x34`	`0x8`	`CountOffsetPair`	Dictates paths for entities to follow or act upon.
zones	`0x3C`	`0x8`	`CountOffsetPair`	Describes an area in the level in which something may occur consistently or conditionally.
course info	`0x44`	`0x8`	`CountOffsetPair`	Indicates completion for Mara's race.
common gimmick name offset	`0x4C`	`0x4`	`u32`	The string bank for common gimmick names starts here, relative to the start of the file.
collision type name offset	`0x50`	`0x4`	`u32`	The string bank for collision type names starts here, relative to the start of the file.
wall label name offset	`0x54`	`0x4`	`u32`	The string bank for the labels of labeled walls starts here, relative to the start of the file.

Walls

Internally called ColDataSeg. Size = 0x20

field	offset	size	data type	description
start position	`0x0`	`0x8`	`Vec2f`
end position	`0x8`	`0x8`	`Vec2f`
normalized vector	`0x10`	`0x8`	`Vec2f`	This is what handles proper collision. See calculation below.¹
index	`0x18`	`0x4`	`u32`	The index of the wall.
collision type index	`0x1C`	`0x4`	`u32`	Referencing the collision type name bank, the index of the collision type.

1 - The normalized vector is calculated as such:

Vec2f GetNormalizedVector(Vec2f start, Vec2f end) {
	Vec2f direction = Vec2f(end.x - start.x, end.y - start.y);
	float magnitude = sqrt(pow(direction.x, 2.0f) + pow(direction.y, 2.0f));
	Vec2f normalized = Vec2f(direction.x / magnitude, direction.y / magnitude);

	Vec2f result = Vec2f(-normalized.y, normalized.x);
	return result;
}

Labeled Walls

Internally called ColDataSegLabel. This builds off of the existing wall structure, with an additional field. Size = 0x24

field	offset	size	data type	description
label index	`0x20`	`0x4`	`u32`	Referencing the wall label name bank, the index of the label.

Common Gimmicks

Size = 0x188

field	offset	size	data type	description
name index	`0x0`	`0x4`	`u32`	Referencing the common gimmick name bank, the index of the common gimmick name. This name is in ShiftJIS and not ASCII.
position	`0x4`	`0xC`	`Vec3f`
parameters	`0x10`	`0x178`	`CommonGimmickParams`

Gimmicks

Size = 0x124

field	offset	size	data type	description
name	`0x0`	`0x30`	`char[0x30]`	ASCII.
unknown	`0x30`	`0x10`	`char[0x10]`	This is often set to all 0s. It's not clear what this is used for.
position	`0x40`	`0xC`	`Vec3f`
parameters	`0x4C`	`0xD8`	`MapdataParams`

Paths

Size > 0x11C as the structure is variable size

field	offset	size	data type	description
name	`0x0`	`0x20`	`char[0x20]`
type	`0x20`	`0x20`	`char[0x20]`	(author's note: I remember that this is a type field, but I don't remember any examples)
params	`0x40`	`0xD8`	`MapdataParams`
number of points	`0x118`	`0x4`	`u32`
points	`0x11C`	`0x8` * number of points	`Vec2f[number of points]`

Zone

Size = 0x128

field	offset	size	data type
name	`0x0`	`0x20`	`char[0x20]`
unknown	`0x20`	`0x20`	`char[0x20]`
params	`0x40`	`0xD8`	`MapdataParams`
zone start	`0x118`	`0x8`	`Vec2f`
zone end	`0x120`	`0x8`	`Vec2f`

Course Info