ASB

ASB (Animation Sequence Binary) is a file format used to store animation sequences for actors in recent Nintendo EPD games such as The Legend of Zelda: Tears of the Kingdom and Nintendo Switch Sports. This article is primarily aimed at the version that appears in Tears of the Kingdom (v0x0417). Other ASB versions include 0x304 (Ring Fit Adventure), 0x3FB (Labo Toy-Con 04 and Game Builder Garage), 0x407 (Animal Crossing: New Horizons), 0x40F (Nintendo Switch Sports), 0x410 (Splatoon 3), and 0x418 (Super Mario Bros. Wonder). ASB files can be found in the AS folder of the romfs as well as the AS folder of certain pack files.

File Structure

ASB is a little endian format which consists of node pathways triggered by AS commands. When an AS command is called, it runs the sequence of nodes connected to it which trigger and control animations and animation logic. Nodes are arranged in an array and referenced and accessed by their array index. Despite the presence of animation events in ASB files, these events do not appear to be used by the game.

All string offsets in the file are relative to the start of the string pool and name hashes are 32-bit murmur3 hashes. There are six possible parameter types: string, int (32-bit signed integer), float (32-bit floating point number), bool, vector3f, and pointer (object pointer).

Section Order

1. File Header (0x6C bytes in version 0x417, 0x68 bytes in version 0x40F)
2. AS Commands
3. Nodes
4. Event Entry Offsets
5. Node Bodies
6. Sync Data Entry Indices
7. Sync Data
8. State Transitions
9. Events
10. Transitions
11. Command Groups
12. AS Blackboard Parameters
13. Partials
14. Bone Groups
15. Calculation Presets
16. Valid Tag List
17. Tag Groups
18. Expression Binary
19. AS Markings
20. Material Blend Settings
21. Enum Resolve Table
22. String Pool

Sections

File Header

File Header

Offset	Size	Type	Description
0x00	0x04	char[4]	Magic - "ASB "
0x04	0x04	u32	Version (0x0417 in Tears of the Kingdom, 0x040F in Nintendo Switch Sports and Splatoon 3)
0x08	0x04	u32	Filename Offset
0x0C	0x04	u32	AS Command Count
0x10	0x04	u32	Node Count
0x14	0x04	u32	Event Count
0x18	0x04	u32	Partial Count
0x1C	0x04	u32	Sync Data Entry Count
0x20	0x04	u32	AS Blackboard Parameters Offset
0x24	0x04	u32	String Pool Offset
0x28	0x04	u32	Enum Resolve Table Offset
0x2C	0x04	u32	State Transitions Offset
0x30	0x04	u32	Event Entries Offset Array Offset
0x34	0x04	u32	Partials Offset
0x38	0x04	u32	Sync Data Offset
0x3C	0x04	u32	Sync Data Indices Array Offset
0x40	0x04	u32	Calculation Presets Offset
0x44	0x04	u32	Calculation Preset Count
0x48	0x04	u32	Bone Groups Offset
0x4C	0x04	u32	Bone Group Count
0x50	0x04	u32	String Pool Size
0x54	0x04	u32	Transitions Offset
0x58	0x04	u32	Tag List Offset
0x5C	0x04	u32	String Triplets Offset
0x60	0x04	u32	EXB Offset (empty if section does not exist)
0x64	0x04	u32	Command Groups Offset (empty if section does not exist)
0x68	0x04	u32	Material Blend Settings Offset (version 0x417 only)

ASB Parameter

Parameter<T>

Offset	Size	Type	Description
0x00	0x04	u32	Flags and Index
0x04	0x04 or 0x0C	T	Value

If the top bit of the flags is set, then the bottom two bytes of the flags become an index value. If it is not set, then the provided value is value of the parameter. If flags & 1 << 0x18 != 0, then the index is an expression index (EXB) and the normal value field becomes the input value for the expression. If flags & 1 << 0x1e != 0, then the index is a calculation preset index. Note, this is only applicable if the parameter is a float. Otherwise, if flags & 1 << 0x19 != 0, then the index specifies the command data type. 0 is the current frame normalized (i.e. (current_frame - start_frame)/total_duration), 1 and 2 are random float values between 0.0 and 1.0, 3 is an unknown string value, 4 is the command's fade in frame, and 6 is an unknown float value. Note, this only applies if the parameter is a float or a string. In all other cases, the index is a blackboard index and value of the parameter is the value of the corresponding blackboard parameter. For float parameters specifically, flags >> 0x1a & 3 specifies the exact parameter source. 0 is a float blackboard parameter while 1, 2, or 3 are a vector3f blackboard parameter with 1, 2, and 3 being the x, y, and z components respectively.

AS Commands

AS Command

Offset	Size	Type	Description
0x00	0x04	u32	Name Offset
0x04	0x04	u32	Tag Entry Offset (version 0x417+)
0x08	0x08	Parameter<float>
0x10	0x08	Parameter<bool>	Is Ignore Same Command
0x18	0x04	u32	Interpolation Type (uncertain, but 0 = unspecified, 1 = no model morph, 3 = enable local bone morph, 4 = enable inertial blend)
0x1C	0x10	u32	GUID
		u16
		u16
		u8[2]
		u8[6]
0x2C	0x02	u16	Child Node Index
0x2E	0x02	u16

Nodes

Node

Offset	Size	Type	Description
0x00	0x02	AsbNodeType	Node Type
0x02	0x01	u8	Sync Data Count
0x03	0x01	u8	Does Not Have State Transition
0x04	0x04	u32	Tag Entry Offset
0x08	0x04	u32	Node Body Offset
0x0C	0x02	u16	Calculation Preset Index
0x0E	0x02	u16	Calculation Preset Count
0x10	0x02	u16	Sync Data Index Array Index
0x12	0x02	u16	AS Markings Index (-1 for index)
0x14	0x10	u32	GUID
		u16
		u16
		u8[2]
		u8[6]

AsbNodeType

Value (Hex)	Value (Dec)	Node Type
0x01	1	FloatSelector
0x02	2	StringSelector
0x03	3	SkeletalAnimation
0x04	4	State
0x05	5
0x06	6	OneDimensionalBlender
0x07	7	Sequential
0x08	8	IntSelector
0x09	9	Simultaneous
0x0A	10	Event
0x0B	11	MaterialAnimation
0x0C	12	FrameController
0x0D	13	DummyAnimation
0x0E	14	RandomSelector
0x0F	15
0x10	16	PreviousTagSelector
0x11	17	BonePositionSelector
0x12	18	BoneVisibilityAnimation
0x13	19	InitialFrame
0x14	20	BoneBlender
0x15	21	BoolSelector
0x16	22	Alert
0x17	23	SubtractAnimation
0x18	24	ShapeAnimation
0x19	25