CLYT (.bclyt) is the layout format used on the 3DS. It stands for (Binary) CTR Layout, and is similar to the RLYT format used on the Wii.

Offset	Size	Type	Description
0x00	0x4	String	Signature (CLYT)
0x04	0x2	UInt16	Byte Order Mark
0x06	0x2	UInt16	Header Length
0x08	0x4	UInt32	Revision
0x0C	0x4	UInt32	File Size
0x10	0x2	UInt16	Nr Sections
0x12	0x2	UInt16	Padding

lyt1 (Layout 1) #

0x00

0x4

String

Signature (lyt1)

0x04

0x4

UInt32

Section Size

0x08

0x4

UInt32

Origin type

Value	Meaning
0	Classic
1	Normal

0x0C

0x8

Vector2

Canvas Size

txl1 (Texture List 1) #

Offset	Size	Type	Description
0x00	0x4	String	Signature (txl1)
0x04	0x4	UInt32	Section Size
0x08	0x4	UInt32	Nr Textures = N
0x0C	N * 4	UInt32[]	Texture Name Offsets (relative to the start of this array)

After this, the null terminated names follow.

fnl1 (Font List 1) #

Offset	Size	Type	Description
0x00	0x4	String	Signature (fnl1)
0x04	0x4	UInt32	Section Size
0x08	0x4	UInt32	Nr Fonts = N
0x0C	N * 4	UInt32[]	Font Name Offsets (relative to the start of this array)

After this, the null terminated names follow.

mat1 (Materials 1) #

Offset	Size	Type	Description
0x00	0x4	String	Signature (mat1)
0x04	0x4	UInt32	Section Size
0x08	0x4	UInt32	Nr Materials = N
0x0C	N * 4	UInt32[]	Material Entry Offsets (relative to the start of this section)

After this, the material entries follow.

0x00

0x14

String

Material Name

0x14

0x4

RGBA8

Tev Color (Buffer Color?)

0x18

RGBA8[6]

Tev Constant Colors

0x30

0x4

UInt32

Flags / bitfield

Bit	Flag / data
0-1	Nr texMap
2-3	Nr texMatrix
4-5	Nr texCoordGen
6-8	Nr tevStage
9	Has alphaCompare
10	Has blendMode
11	Use Texture Only

Texture Map Entry #

0x00

0x2

UInt16

Texture Index

0x02

0x1

Byte

Bitfield

Bit	Data
0-1	Wrap S (Clamp = 0, Repeat = 1, Mirror = 2)
2-3	Min Filter (0 = Near, 1 = Linear)

0x03

0x1

Byte

Bitfield

Bit	Data
0-1	Wrap T (Clamp = 0, Repeat = 1, Mirror = 2)
2-3	Mag Filter (0 = Near, 1 = Linear)

Texture Matrix Entry #

Offset	Size	Type	Description
0x00	0x8	Vector2	Translation
0x08	0x4	Single	Rotation
0x0C	0x8	Vector2	Scale

Texture Coordinate Generation Entry #

0x00

0x1

UInt8

Type

Value	Meaning
0	2x4 matrix

0x01

0x1

UInt8

Source (N = Tex N, max 2)

0x02

0x2

UInt8[]

Padding

TODO: tevStage, alphaCompare, blendMode, etc…

pan1(Pane 1) #

Defines a Null pane, used mostly to keep panes grouped in hierarchies or to control the children of a given pan1 without having to do so individually.

0x00

0x4

String

Signature (pan1)

0x04

0x4

UInt32

Section Size

0x08

0x1

UInt8

Flags

Bit	Flag
0	Visible
1	InfluencedAlpha
2	LocationAdjust

0x09

0x1

UInt8

Origin (1 = centered, 2 = right, 3 = left, )

0x0A

0x1

UInt8

Alpha

0x0B

0x1

UInt8

Padding

0x0C

0x10

String

Pane name

0x1C

0x8

String

Data

0x24

0xC

Vector3

Translation

0x30

0xC

Vector3

Rotation

0x3C

0x8

Vector2

Scale

0x44

0x8

Vector2

Size

pic1(Picture 1) #

pic1 represents a picture that can be displayed in a layout. The first 0x4C bytes are defined the same as pan1 with minor differences.

Offset	Size	Type	Description
0x00	0x4	String	Signature (pic1)
0x04	0x4	UInt32	Section size (including the texture coordinates)
Same as pan1 from 0x8 to 0x4c
0x4C	0x4	RGBA8	Top left vertex color
0x50	0x4	RGBA8	Top right vertex color
0x54	0x4	RGBA8	Bottom left vertex color
0x58	0x4	RGBA8	Bottom right vertex color
0x5C	0x2	UInt16	Material ID
0x5E	0x2	UInt16	Nr texture coordinates = N
Texture coordinates entry
0x60 + (N-1) * 0x20	0x8	Vector2	Top left vertex texture coordinate
0x64 + (N-1) * 0x20	0x8	Vector2	Top right vertex texture coordinate
0x68 + (N-1) * 0x20	0x8	Vector2	Bottom left vertex texture coordinate
0x6C + (N-1) * 0x20	0x8	Vector2	Bottom right vertex texture coordinate

txt1 (Text 1) #

A textbox used in layouts. The first 0x4C bytes are defined the same as pan1 with minor differences.

Offset	Size	Type	Description
0x00	0x4	String	Signature (txt1)
0x04	0x4	UInt32	Section size (including the textbox string)
Same as pan1 from 0x8 to 0x4c
0x4C	0x2	Unknown	Flags (H Direction?)
0x4E	0x2	Unknown	Flags (V Direction?)
0x50	0x4	UInt32	Material ID
0x54	0x2	Unknown	Flags (Line alignment?)
0x56	0x2	Unknown	Padding
0x58	0x4	UInt32	Offset from signature to beginning of the string
0x5C	0x4	RGBA8	Font top color
0x60	0x4	RGBA8	Font bottom color
0x64	0x8	Vector2	Font scale
0x6C	0x4	Float	Horizontal font spacing
0x70	0x4	Float	Vertical font spacing
0x74	User defined	String	Textbox text (must be multiple of 4), can be usd1

wnd1 (Window 1) #

A more complex type of image pane, where the user can define the content, the corners and the sides of it, depending on what mode it’s set to.

0x00

0x4

String

Signature (wnd1)

0x04

0x4

UInt32

Section size (including the texture coordinates)

Same as pan1 from 0x8 to 0x4c

0x4C

0x4

float

Coordinate 1

0x50

0x4

float

Coordinate 2

0x54

0x4

float

Coordinate 3

0x58

0x4

float

Coordinate 4

0x5C

0x1

Byte

Number of frames (n)

0x5D

0x1

Byte

Flag

0x5E

0x2

UInt16

Padding

0x60

0x4

UInt32

Window content offset (Points to 0x68)

0x64

0x4

UInt32

Window frame offsets, offset to offsets of the materials for the frames. (W)

0x68

0x4

RGBA8

Content box top left vertex color

0x6C

0x4

RGBA8

Content box top right vertex color

0x70

0x4

RGBA8

Content box bottom left vertex color

0x74

0x4

RGBA8

Content box bottom right vertex color

0x78

0x2

UInt16

Content box Material ID

0x7A

0x2

UInt16

Number of Texture coordinates (N)

Texture coordinates entry

0x7C + (N-1) * 0x20

0x8

Vector2

Top left vertex texture coordinate

0x84 + (N-1) * 0x20

0x8

Vector2

Top right vertex texture coordinate

0x8C + (N-1) * 0x20

0x8

Vector2

Bottom left vertex texture coordinate

0x94 + (N-1) * 0x20

0x8

Vector2

Bottom right vertex texture coordinate

Window frames

0x(W)

0x4 * n

UInt32

Offsets to frame materials

0x(W)

0x4 * n

Window frame

Offset	Size	Type	Description
0x0	UInt16	0x2	Frame Material ID
0x2	Byte	0x1	Flip Type
0x3	Byte	0x1	Padding

Below is a table of possible material flip types. ^{(From
Mario Kart Wii Wiki)}

Type	Description
0	None
1	Flip (Horizontal)
2	Flip (Vertical)
3	Rotate 90 Degrees
4	Rotate 180 Degrees
5	Rotate 270 Degrees

bnd1 (Bounding 1) #

Same data structure as Panes, but used to limit interaction with buttons.

Offset	Size	Type	Description
0x00	0x4	String	Signature (bnd1)
0x04	0x4	UInt32	Section size (including the texture coordinates)
Same as pan1 from 0x8 to 0x4c

pas1 (Pane Start 1) #

Marks the start of a pane hierarchy, with the parent being the previous pane.

Offset	Size	Type	Description
0x00	0x4	String	Signature (pas1)
0x04	0x4	UInt32	Section Size

pae1 (Pane End 1) #

Marks the end of a pane hierarchy.

Offset	Size	Type	Description
0x00	0x4	String	Signature (pae1)
0x04	0x4	UInt32	Section Size

grp1 (Group 1) #

Starts a pane group, which can be inside other pane groups.

Offset	Size	Type	Description
0x00	0x4	String	Signature (grp1)
0x04	0x4	UInt32	Section Size
0x08	0x10	String	Group Name
0x18	0x4	UInt32	Nr Pane References (=N)
0x1C	0x10 * N	String[N]	Pane References

grs1 (Group Start 1) #

Starts a group hierarchy.

Offset	Size	Type	Description
0x00	0x4	String	Signature (grs1)
0x04	0x4	UInt32	Section Size

gre1 (Group End 1) #

Ends a group hierarchy.

Offset	Size	Type	Description
0x00	0x4	String	Signature (gre1)
0x04	0x4	UInt32	Section Size

usd1 (User Data 1) #

Contains a dictionary with strings as keys and variable values

Offset	Size	Type	Description
0x00	0x4	String	Signature (usd1)
0x04	0x4	UInt32	Section Size
0x08	0x4	UInt32	Number of entries (= N)
0xC	0xC * N // Variable	Entries[]	Entries

User Entries #

Where an entry is as follows:

0x0

0x4

UInt32

Key offset (from start of this entry) to null-terminated ascii string that serves as key.

0x4

UInt32

Value offset (from start of this entry).

0x8

0x2

UInt16

Number of entries or string length.

0xA

0x2

UInt16

Value type

Value	Type
0x0	String
0x1	Int
0x2	Float

Tools #

🔗 Every File Explorer and 🔗 Switch Toolbox both have limited support for viewing these.
🔗 Clypo allows exporting these files to yml and importing back to bclyt but it only supports scale, size, translation and rotation of panes.

CLYT Format

Header #

lyt1 (Layout 1) #

txl1 (Texture List 1) #

fnl1 (Font List 1) #

mat1 (Materials 1) #

Texture Map Entry #

Texture Matrix Entry #

Texture Coordinate Generation Entry #

pan1(Pane 1) #

pic1(Picture 1) #

txt1 (Text 1) #

wnd1 (Window 1) #

bnd1 (Bounding 1) #

pas1 (Pane Start 1) #

pae1 (Pane End 1) #

grp1 (Group 1) #

grs1 (Group Start 1) #

gre1 (Group End 1) #

usd1 (User Data 1) #

User Entries #

Tools #

See also #