CMB (File Format)

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CMB (Citra Model Binary) is a file format used in Nintendo 3DS games such as The Legend of Zelda: Ocarina of Time 3D and The Legend of Zelda: Majora's Mask 3D, and they contain 3D model and texture information.

File Format

The file byte order is always little endian.

Header

The file starts with a header that is 0x20 bytes long.

Offset	Type	Description
0x00	Char[4]	File magic. Always cmb ‌ in ASCII.
0x04	UInt32	File size in bytes.
0x08	Int32	Probably a version number. 0x6 for OoT3D and 0xA for MM3D.
0x0C	Int32	Unknown. Always 0.
0x10	String	Null-terminated string of the model name and padding.

Section Data

Offset	Type	Description
0x00	Int32	Number of indices.
0x04	UInt32	skl ‌ offset.
If version = 0xA
0x08	UInt32	qtrs offset.
P = current position
P	UInt32	mats offset.
P + 0x04	UInt32	tex ‌ offset.
P + 0x08	UInt32	sklm offset.
P + 0x0C	UInt32	luts offset.
P + 0x10	UInt32	vatr offset.
P + 0x14	UInt32	Index Buffer offset.
P + 0x18	UInt32	Texture Data offset.
If version = 0xA
P + 0x1C	UInt32	Unknown. Always 0. Maybe padding?

skl ‌

The skl ‌ section contains skeleton information.

Header

Offset	Type	Description
0x00	Char[4]	Section magic. Always skl ‌ in ASCII.
0x04	UInt32	Section size in bytes.
0x08	Int32	Number of bones.
0x0C	Int32	Unknown.

Bone

Offset	Type	Description
0x00	Int16	Bone index.
0x02	Int16	Parent bone index. -1 if none.
0x04	Float[3]	Bone scale.
0x10	Float[3]	Bone rotation.
0x1C	Float[3]	Bone translation.
If version = 0xA
0x28	UInt32	Unknown.

qtrs

The qtrs section contains quadtree information. It's only used on version 0xA.

Header

Offset	Type	Description
0x00	Char[4]	Section magic. Always qtrs in ASCII.
0x04	UInt32	Section size in bytes.
0x08	Int32	Number of Bounding Boxes.
0x0C	Int32	Unknown. Always 0?
0x10	Int32	Unknown. Always 0?

Bounding Box

Offset	Type	Description
0x00	Float[3]	Minimum box position.
0x0C	Float[3]	Maximum box position.
0x18	Int32	Unknown. Usually -1.
0x1C	Int32	Unknown. Usually -1.
0x20	UInt32	Unknown. Always 0. Maybe padding?

mats

The mats section contains material information.

Header

Offset	Type	Description
0x00	Char[4]	Section magic. Always mats in ASCII.
0x04	UInt32	Unknown. Seems to be a size value, but it does not match with the section's size.
0x08	Int32	Number of Materials.

Material

Each material has a header, 3 Texture Sampler sections, .

Header

Offset	Type	Description
0x00	Byte[8]	Unknown flags.
0x08	Int32	Unknown.
0x0C	Int32	Unknown.

Texture Sampler

Offset	Type	Description
0x10	Int16	Texture ID. -1 if none.
0x12	Int16	Unknown.
0x14	UInt16	Texture MinFilter: 0x2600 = GL_NEAREST 0x2601 = GL_LINEAR 0x2700 = GL_NEAREST_MIPMAP_NEAREST 0x2701 = GL_LINEAR_MIPMAP_NEAREST 0x2702 = GL_NEAREST_MIPMAP_LINEAR 0x2703 = GL_LINEAR_MIPMAP_LINEAR 0x8146 = GL_FILTER4_SGIS 0x8170 = GL_LINEAR_CLIPMAP_LINEAR_SGIX 0x8184 = GL_PIXEL_TEX_GEN_Q_CEILING_SGIX 0x8185 = GL_PIXEL_TEX_GEN_Q_ROUND_SGIX 0x8186 = GL_PIXEL_TEX_GEN_Q_FLOOR_SGIX 0x848D = GL_NEAREST_CLIPMAP_NEAREST_SGIX 0x844E = GL_NEAREST_CLIPMAP_LINEAR_SGIX 0x844F = GL_LINEAR_CLIPMAP_NEAREST_SGIX
0x16	UInt16	Texture MagFilter: 0x2600 = GL_NEAREST 0x2601 = GL_LINEAR 0x8097 = GL_LINEAR_DETAIL_SGIS 0x8098 = GL_LINEAR_DETAIL_ALPHA_SGIS 0x8099 = GL_LINEAR_DETAIL_COLOR_SGIS 0x80AD = GL_LINEAR_SHARPEN_SGIS 0x80AE = GL_LINEAR_SHARPEN_ALPHA_SGIS 0x80AF = GL_LINEAR_SHARPEN_COLOR_SGIS 0x8146 = GL_FILTER4_SGIS 0x8184 = GL_PIXEL_TEX_GEN_Q_CEILING_SGIX 0x8185 = GL_PIXEL_TEX_GEN_Q_ROUND_SGIX 0x8186 = GL_PIXEL_TEX_GEN_Q_FLOOR_SGIX
0x18	UInt16[2]	Texture Wrap Mode: 0x2900 = GL_CLAMP 0x2901 = GL_REPEAT 0x812D = GL_CLAMP_TO_BORDER 0x812F = GL_CLAMP_TO_EDGE 0x8370 = GL_MIRRORED_REPEAT
0x1C	Byte[12]	Unknown.

Tools

The following tools can handle CMB files:

• N3DSCmbViewer, by xdanieldzd.