ASB

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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