FTXP (File Format)
FTXP files (caFe TeXture Pattern animation) are texture pattern animation files found in BFRES files in the 6th index group. It contains animation data about which texture that should be rendered at what time. Unless otherwise noted, all offsets in the file are relative to themselves.
An FTXP file begins with an FTXP 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.
FTXP shares many similarities with the FSKA, FSHU, 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.
Every FTXP begins with an 0x38 byte FTXP header.
|0x00||4||Char||"FTXP" 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||2||UInt16||Flags. Set of bits packed as xxxxxxxx xxxxxLxB, controlling how to play the animation and what data is stored. The following flags are possible:
|0x0E||2||UInt16||User Data entry count.|
|0x14||2||UInt16||Texture Reference count. Number of Texture Reference structures referenced by the Texture Reference index group.|
|0x16||2||UInt16||Material Pattern Animation count. Number of elements in the Material Pattern Animation array.|
|0x18||4||UInt32||Pattern Animation Info count, the total number of Pattern Animation Info structures in all Material Pattern Animations.|
|0x1C||4||UInt32||Curve count, the total number of Curve structures in all Material Pattern Animations.|
|0x24||4||Int32||Model offset. Points to the affected FMDL model.|
|0x28||4||Int32||Bind index array offset.|
|0x2C||4||Int32||Material Pattern Animation array offset.|
|0x30||4||Int32||Texture Reference index group offset. The reference structures point to FTEX file names and FTEX headers.|
|0x34||4||Int32||User Data index group offset.|
|0x38||End of FTXP header|
The header points to an array of UInt16 elements with as many elements as specified in Material Pattern 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 Pattern Animation
The header points to an array of Material Pattern Animation structures with as many elements as specified in Material Pattern Animation count, each of 0x1C bytes size. They describe info about the material that is animated.
|0x00||2||UInt16||Pattern Animation Info count.|
|0x04||4||Int32||Start Curve index, relative to the whole FTXP subfile (an array where all Material Pattern Animation Curves would be stored together, in the order of which they appear in the subfile).|
|0x08||4||Int32||Start Pattern Animation Info index, relative to the whole FTXP subfile (an array where all Pattern Animation Infos would be stored together, in the order of which they appear in the subfile).|
|0x0C||4||Int32||Animation name offset.|
|0x10||4||Int32||Pattern Animation Info array offset.|
|0x14||4||Int32||Curve array offset.|
|0x18||4||Int32||Base Value array offset. Each element is an UInt16 with unknown purpose, apparently storing initial state.|
|0x1C||End of Material Pattern Animation|
Pattern Animation Info
Each Material Pattern Animation points to an array of Pattern Animation Info structures, with as many elements as specified in Pattern Animation Info count, each of 0x08 bytes size.
|0x00||1||SByte||Curve index in the Material Pattern Animation Curve array.|
|0x01||1||SByte||Sub bind index, index of the Texture Reference in the FTXP subfile. Can be -1 for no binding.|
|0x08||End of Pattern Animation Info|
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 188.8.131.52, they are of 0x20 bytes size).
|0x00||2||UInt16||Flags. Sets of bits packed as xxxxxxxx xCCCKKFF.
|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 >= 184.108.40.206|
|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|
|0x18||4||Int32||Frame array offset.|
|0x1C||4||Int32||Key array offset.|
|0x20||End of Curve|
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.
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.
The elements apparently represent the key values directly.
For linearly interpolated curves, 2 elements are stored per key:
- Value at which the key is set. To get the final value, scale and then offset it.
- 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.|
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.
The Curve targets which control what exactly is animated over time are not yet known.