FSHU (File Format)

Under Construction

This article is not finished. Help improve it by adding accurate information or correcting grammar and spelling.

The FSHU (caFe SHader parameter animation Uber) subfile stores shader parameter animations. It appears as a subfile of a BFRES file in the 3rd index group for general parameter animations, in the 4th index group for color animations, and in the 5th index group for SRT texture animations.

Format

An FSHU file begins with an FSHU header. This is then followed by a number of sections pointed to by the header, many of which can occur multiple times. The purpose of these sections is described in the table below.

FSHU shares many similarities with the FSKA, FTXP, FVIS, FSHA and FSCN subfiles, which mostly only differ in the structure describing what is changed by animations over time, but reusing the same animation curve and key structures, and even headers being very similar to one another.

Header (FSHU)

Every FSHU begins with an 0x34 byte FSHU header.

Offset	Size	Type	Description
0x00	4	Char[4]	"FSHU" file identifier, ASCII string.
0x04	4	Int32	File name offset (without file extension).
0x08	4	Int32	File path offset, the path of the file this data was originally created from. Stripped in Mario Kart 8 files, always pointing to an empty string at the end of the BFRES string table.
0x0C	4	UInt32	Flags. Set of bits controlling how data is stored. The following flags are possible: Bit (0-based) Description 0 Curve is baked. 2 Animation is looping.
0x10	4	Int32	Frame count.
0x14	2	UInt16	Material Animation count. Number of elements in the Material Animation array.
0x16	2	UInt16	User Data entry count.
0x18	4	Int32	Parameter Animation Info count, the total number of Parameter Animation Info structures in all Material Animations.
0x1C	4	UInt32	Curve count, the total number of Curve structures in all Material Animations.
0x20	4	UInt32	Baked length.
0x24	4	Int32	Model offset. Points to the affected FMDL model.
0x28	4	Int32	Bind index array offset.
0x2C	4	Int32	Material Animation array offset.
0x30	4	Int32	User Data index group offset.
0x34	End of FSHU header

Bind Indexes

The header points to an array of UInt16 elements with as many elements as specified in Material Animation count. It holds indices to materials, but an index can be 0xFFFF to reference no material. The exact purpose of this array is unknown. The end of the array is aligned to 4 bytes.

Material Animation

The header points to an array of Material Animation structures with as many elements as specified in Material Animation count, each of 0x20 bytes size.

Offset	Size	Type	Description
0x00	2	UInt16	Parameter Animation Info count.
0x02	2	UInt16	Curve count.
0x04	2	UInt16	Animation Constant count.
0x06	2	—	Padding.
0x08	4	Int32	Start Curve index, relative to the whole FSHU subfile (an array where all Material Animation Curves would be stored together, in the order of which they appear in the subfile).
0x0C	4	Int32	Start Parameter Animation Info index, relative to the whole FSHU subfile (an array where all Parameter Animation Infos would be stored together, in the order of which they appear in the subfile).
0x10	4	Int32	Animation Name offset.
0x14	4	Int32	Parameter Animation Info array offset.
0x18	4	Int32	Curve array offset.
0x1C	4	Int32	Animation Constant array offset.
0x20	End of Material Animation

Parameter Animation Info

Each Material Animation points to an array of Parameter Animation Info structures, with as many elements as specified in Parameter Animation Info count, each of 0x10 bytes size.

Offset	Size	Type	Description
0x00	2	UInt16	Start Curve index in the Curve array of the Material Animation.
0x02	2	UInt16	Float Curve count.
0x04	2	UInt16	Int Curve count.
0x06	2	UInt16	Start Animation Constant index in the Constant array of the Material Animation.
0x08	2	UInt16	Animation Constant count.
0x0A	2	UInt16	Sub bind index.
0x0C	4	Int32	Name offset.
0x10	End of Parameter Animation Info

Animation Constant

Each Material Animation points to an array of Animation Constants, with as many elements as specified in Constant count, each of 0x08 bytes size.

Offset	Size	Type	Description
0x00	4	UInt32	Target offset.
0x04	4	Int32 / Single	Value of this constant.
0x08	End of Animation Constant

Curve

Curves store how animations are performed over time and store the required keys and values for this. They appear in multiple animation subfiles, and their header is of 0x24 bytes size (for BFRES versions earlier than 3.4.0.0, they are of 0x20 bytes size).

Offset	Size	Type	Description
0x00	2	UInt16	Flags. Sets of bits packed as xxxxxxxx xCCCKKFF. FF determines the data type of frames in the Frame array. Value Size Type 0 4 Single 1 2 16-bit fixed point value (1 bit sign, 10 bits integral and 5 bits fractional). To convert to Single, use Float(x) / (1 << 5). To retrieve from Single, use Round(x * (1 << 5)) 2 1 Byte KK determines the data type of keys in the Key array. Value Size Type 0 4 Single 1 2 Int16 2 1 SByte CCC determines what kind of curve data is stored, resulting in a different number of elements stored per Key. They are used to set the key values and control the interpolation from one key to the next. Value Description Elements per Key 0 Cubic Single 4 (hermite interpolation) 1 Linear Single 2 (linear interpolation) 2 Baked Single 1 (no interpolation) 4 Step Integer 1 (no interpolation) 5 Baked Integer 1 (no interpolation) 6 Step Boolean 1 (no interpolation) 7 Baked Boolean 1 (no interpolation)
0x02	2	UInt16	Key count.
0x04	4	UInt32	Target Offset, an offset in bytes into the corresponding Animation Data structure to animate the field at that relative address.
0x08	4	Single	Start frame, the first frame at which a key is placed.
0x0C	4	Single	End frame, the last frame at which a key is placed.
0x10	4	Int32 / Single	Data scale, multiplier to the raw key values to get the final result. Together with Data offset, it is chosen carefully to consider an optimal granularity between the stored values.
0x14	4	Single	Data offset, added to the raw values (after multiplying them with Data scale) to get the final key value.
if BFRES version >= 3.4.0.0
0x18	4	Single	Data delta, stores the difference between the first and last key value.
0x1C	4	Int32	Frame array offset.
0x20	4	Int32	Key array offset.
0x24	End of Curve
else
0x18	4	Int32	Frame array offset.
0x1C	4	Int32	Key array offset.
0x20	End of Curve

Frames

The Curve header points to a Frame array which stores values controlling at which frame a Key from the Key array is placed. Thus, the array has as many elements as specified in Key count. The data type of the frames is given in the Curve's Flags.

The end of the array is aligned to 4 bytes.

Keys

The Curve header points to a Key array which stores the key values and additional values to interpolate the curve from one point to the next. Thus, the array has as many elements as specified in Key count, multiplied by the number of elements stored per key (depending upon the CCC Curve Type bits in the Curve Flags as described above). The data type of each element is given by the KK Key Type bits in the Curve Flags.

The end of the array is aligned to 4 bytes.

Step Curves

The elements apparently represent the key values directly.

Linear Curves

For linearly interpolated curves, 2 elements are stored per key:

1. Value at which the key is set. To get the final value, scale and then offset it.
2. Delta to value at next frame to which the curve linearly runs. To get the final value, scale it. If there is no next frame, this is always 0.

A key can be discarded by the next key if that one is stored at the same frame. In that case, only the value of the next key is stored, and the delta of the previous key is adjusted to run to the value of the now discarded key.

This example curve's keys are stored as SByte elements. The curve scale was computed as 2, the offset as 200 and the curve delta (if available in the BFRES version) as 300. Due to the lower key in frame 20 being discarded in favor of the higher key, only 3 keys are stored in 6 elements as follows.

Point	Array Index	Raw Value	*2 (Scale)	+200 (Offset)	Notes
0,0	0	-100	-200	0	Initial key with value 0.
(20,254)	1	127	254	-	Delta to end value of initial key at next frame.
20,254	-	-	-	-	This key is discarded in favor of the next.
20,400	2	100	200	400	Overrides previous key.
(30,300)	3	-50	-100	-	End value of overriding key at next frame.
30,300	4	50	100	300	Value of fourth (but third stored) key.
(end)	5	0	0	-	Since no frame follows, always 0.

Hermite Curves

For hermite curves, 4 elements are stored for each key. It is unclear how to exactly interprete them to form the curve out of it.