BRK

BRK is a format that stores texture register animations, which allows animating color changes. It consists of the standard animation header, followed by BRK-specific data in the TRK1 chunk, with color data stored in banks at the end.

JSYSTEM Header

The file starts with a standard JSYSTEM header, using a magic of J3D1brk1. BRK files have one chunk, the TRK1 chunk.

Header

Offset	Type	Name	Description
0x00	Chunk Header	Standard JSYSTEM chunk header
0x08	Loop Mode	Loop Mode
0x09	byte	Unknown	(Likely unused)
0x0A	short	Duration	The number of frames in the animation
0x0C	short	Register Color Table Count	The number of animation entries in the register colors table
0x0E	short	Konstant Color Table Count	The number of animation entries in the konstant colors table
0x10	short	Register Red Count	The number of entries in the register red values table
0x12	short	Register Blue Count	The number of entries in the register blue values table
0x14	short	Register Green Count	The number of entries in the register green values table
0x16	short	Register Alpha Count	The number of entries in the register alpha values table
0x18	short	Konstant Red Count	The number of entries in the konstant red values table
0x1A	short	Konstant Blue Count	The number of entries in the konstant blue values table
0x1C	short	Konstant Green Count	The number of entries in the konstant green values table
0x1E	short	Konstant Alpha Count	The number of entries in the konstant alpha values table
0x20	int	Register Animation Data Table Offset	Offset to the start of the register animation data table
0x24	int	Konstant Animation Data Table Offset	Offset to the start of the konstant animation data table
0x28	int	Register Remap Table Offset
0x2C	int	Konstant Remap Table Offset
0x30	int	Register Name Table Offset
0x34	int	Register Name Table Offset
0x38	int	Register Red Table Offset
0x3C	int	Register Green Table Offset
0x40	int	Register Blue Table Offset
0x44	int	Register Alpha Table Offset
0x48	int	Konstant Red Table Offset
0x4C	int	Konstant Green Table Offset
0x50	int	Konstant Blue Table Offset
0x54	int	Konstant Alpha Table Offset

LoopMode

LoopMode is an enum as follows:

Value	Name	Meaning
0x00	Once	The animation plays once and stops on the final frame.
0x01	Once and Reset	The animation plays once and stops on the first frame.
0x02	Loop	The animation loops indefinitely.
0x03	Mirrored Once	The animation plays once, then plays in reverse, then stops on the first frame.
0x04	Mirrored Loop	The animation plays once, then plays in reverse, then the process repeats.

Animation Data

There are 4 animation tracks stored in each animation table, one for each color channel.

Offset	Type	Channel
0x00	TrackData	Red
0x06	TrackData	Green
0x0C	TrackData	Blue
0x12	TrackData	Alpha

TrackData

Each TrackData is 0x06 bytes long, with the following layout:

Offset	Type	Name	Description
0x00	short	Count	Number of keyframes in the track
0x02	short	Index	The index of the first piece of keyframe data
0x04	TangentMode	Tangent Mode	The mode of storing animation curve tangents

TangentMode

TangentMode is an enum as follows:

Value	Name	Meaning
0x00	Symmetric	One tangent value is stored, used for both the incoming and outgoing tangents
0x01	Piece-wise	Two tangent values are stored, the incoming and outgoing tangents, respectively

Animation Curve Data

The tables for individual channels store the component data for that channel. The values are stored as consecutive signed shorts.

Using the Index, Count, and Tangent Mode values for the curves, the decoding is as follows:

1. If the Count field is 1, then there is no curve, and instead, a single value is stored in the table at Index.
2. Otherwise, then if Tangent Mode is Symmetric: Read 3 values per keyframe, with Count keyframes, starting from the table at Index. The three values, are, in order: Time (the frame index), Value, and Tangent (both incoming and outgoing).
3. Otherwise, then Tangent Mode should be Piece-wise. Read 4 values per keyframe, with Count keyframes, starting from the table at Index. The four values, are, in order: Time (the frame index), Value, Incoming Tangent, and Outgoing Tangent.

Calculating the value for an animation track

To calculate a single value for a single animation track, a Hermite spline interpolation should be used. Specifically, choose the two keyframes on either side of the current time, and interpolate using the left's outgoing tangent and value, and the right's incoming tangent and value to build the four control points on a 1D Cubic Hermite spline.