BCK - Revision history

Jasper: minor fixes

2020-07-05T14:50:11Z

minor fixes

LagoLunatic: Fix trackdatas being out of order

2020-03-11T03:01:52Z

Fix trackdatas being out of order

LagoLunatic: Fix one field having wrong data type

2020-03-07T14:08:02Z

Fix one field having wrong data type

Jasper at 01:04, 10 December 2019

2019-12-10T01:04:32Z

Jasper at 00:51, 10 December 2019

2019-12-10T00:51:05Z

Jasper: /* Animation Curve Data */

2019-12-09T23:34:25Z

‎Animation Curve Data

Jasper at 23:34, 9 December 2019

2019-12-09T23:34:04Z

Gamma: Created page with "'''BCK''' is the format that stores bone animation data for BMD and BDL models. It consists of the standard animation header, followed by BCK-specific data in the ANK1 chunk,..."

2016-10-30T02:59:29Z

Created page with "'''BCK''' is the format that stores bone animation data for BMD and BDL models. It consists of the standard animation header, followed by BCK-specific data in the ANK1 chunk,..."

New page

'''BCK''' is the format that stores bone animation data for BMD and BDL models. It consists of the standard animation header, followed by BCK-specific data in the ANK1 chunk, with data stored in banks at the end separated by component type - scale, rotation, and translation.

=Standard Header=

This header is found at the start of all the animation formats. Below is what it looks like for the BCK format.

//0x20/32 bytes long
/*0x00*/ char[4] Magic; // "J3D1"
/*0x04*/ char[4] StudioType; // "bck1"
/*0x08*/ int fileSize;
/*0x0C*/ int numChunks;
// From 0x10 to 0x20 is an array of padding bytes with the value 0xFF/255.

=ANK1=

This follows the standard header and contains data specific to the BCK format.

==Header==

The layout of the header is as follows:

//0x24/36 bytes long, padded out to 0x40/64 bytes
/*0x00*/ string "ANK1";
/*0x04*/ int ank1Size;
/*0x08*/ byte flag;
/*0x09*/ byte angleMultiplier;
/*0x0A*/ short animLength;
/*0x0C*/ short jointAnimationEntryCount; //One for each bone in the model
/*0x0E*/ short scaleFloatBankEntryCount;
/*0x10*/ short rotationShortBankEntryCount;
/*0x12*/ short translateFloatBankEntryCount;
/*0x14*/ int jointAnimationEntriesOffset;
/*0x18*/ int scaleFloatBankOffset;
/*0x1C*/ int rotationShortBankOffset;
/*0x20*/ int translateFloatBankOffset;
//From 0x24 to 0x40 is the standard padding string: "This is padding data to alig".

After this header is the keyframe data.

==Keyframe Data==

There are 9 keyframes for each bone - 1 each for the X, Y, and Z components of scaling, rotation, and translation. The layout of these keyframes is shown below.

//0x36/54 bytes long
// X components
/*0x00*/ Keyframe ScaleX;
/*0x06*/ Keyframe RotationX;
/*0x0C*/ Keyframe TranslationX;
// Y components
/*0x12*/ Keyframe ScaleY;
/*0x18*/ Keyframe RotationY;
/*0x1E*/ Keyframe TranslationY;
// Z components
/*0x24*/ Keyframe ScaleZ;
/*0x2A*/ Keyframe RotationZ;
/*0x30*/ Keyframe TranslationZ;

The keyframes are grouped according to their components, and are always in the order of scale/rotation/translation.

Each keyframe is 6 bytes long, with the following layout:

//0x6/6 bytes long
/*0x00*/ short keyCount; //Number of keys in this keyframe
/*0x02*/ short startingIndex; //Starting index of data in relevant bank
/*0x04*/ short unknownShort; //Either 0 or 1

Thus, a keyframe contains the number of keys that will be interpolated over the course of the animation, the index of the first key in the relevant data bank, and a short with an unknown purpose.

This section is padded to the nearest 32 bytes with the standard padding string.

=Data Banks=

There are 3 data banks after the keyframe data that store the keys for scaling, rotation, and translation. The scale and translation values are stored as floats, but the rotation values are stored as shorts.

Each bank begins with one "default" value that the keyframes can reference when they don't need to sample any keys. For scale, this is 1.0f; for rotation, this is 0; and for translation, this is 0.0f. This default is just the value, but every key after it follows this format:

var Timestamp;
var Value;
var Tangent;

The timestamp and the tangent are stored in the same datatype as the value - float for the scale and translation banks, and short for the rotation bank.

@@ Line 5: / Line 5: @@
 The file starts with a standard [[JSYSTEM#Header|JSYSTEM]] header, using a magic of J3D1bck1. BCK files have one chunk, the ANK1 chunk.
-==Header==
+=ANK1 Chunk=
 {| class="wikitable"
@@ Line 25: / Line 25: @@
 | <center>0x10</center> || short || Rotation Table Count || The number of entries in the rotation table
 |-
-| <center>0x12</center> || short || Translation Table Count || The number of entries in the rotation table
+| <center>0x12</center> || short || Translation Table Count || The number of entries in the translation table
 |-
 | <center>0x14</center> || int || Animation Data Table Offset || Offset to the start of the animation data table

@@ Line 66: / Line 66: @@
 | <center>0x00</center> || TrackData || Scale X || Scale of the X coordinate
 |-
-| <center>0x06</center> || TrackData || Scale Y || Scale of the Y coordinate
+| <center>0x06</center> || TrackData || Rotation X || Rotation of the X coordinate
 |-
-| <center>0x0C</center> || TrackData || Scale Z || Scale of the Z coordinate
+| <center>0x0C</center> || TrackData || Translation X || Translation of the X coordinate
 |-
-| <center>0x12</center> || TrackData || Rotation X || Rotation of the X coordinate
+| <center>0x12</center> || TrackData || Scale Y || Scale of the Y coordinate
 |-
 | <center>0x18</center> || TrackData || Rotation Y || Rotation of the Y coordinate
 |-
-| <center>0x1E</center> || TrackData || Rotation Z || Rotation of the Z coordinate
+| <center>0x1E</center> || TrackData || Translation Y || Translation of the Y coordinate
 |-
-| <center>0x24</center> || TrackData || Translation X || Translation of the X coordinate
+| <center>0x24</center> || TrackData || Scale Z || Scale of the Z coordinate
 |-
-| <center>0x2A</center> || TrackData || Translation Y || Translation of the Y coordinate
+| <center>0x2A</center> || TrackData || Rotation Z || Rotation of the Z coordinate
 |-
 | <center>0x30</center> || TrackData || Translation Z || Translation of the Z coordinate

@@ Line 15: / Line 15: @@
 | <center>0x08</center> || [[BCK#LoopMode|Loop Mode]] || Loop Mode ||
 |-
-| <center>0x09</center> || int || Rotation Frac || Multiplier for fixed-point decimal
+| <center>0x09</center> || byte || Rotation Frac || Multiplier for fixed-point decimal
 |-
 | <center>0x0A</center> || short || Duration || The number of frames in the animation

@@ Line 7: / Line 7: @@
 ==Header==
-The layout of the header is as follows:
+{| class="wikitable"
+|-
- //0x24/36 bytes long, padded out to 0x40/64 bytes
+! Offset                !! Type !! Name !! Description
- /*0x00*/ string "ANK1";
+|-
- /*0x04*/ int ank1Size;
+| <center>0x00</center> || [[JSYSTEM#Chunk_Data|Chunk Header]] || Standard JSYSTEM chunk header
- /*0x08*/ byte flag;
+|-
- /*0x09*/ byte angleMultiplier;
+| <center>0x08</center> || [[BCK#LoopMode|Loop Mode]] || Loop Mode ||
- /*0x0A*/ short animLength;
+|-
- /*0x0C*/ short jointAnimationEntryCount; //One for each bone in the model
+| <center>0x09</center> || int || Rotation Frac || Multiplier for fixed-point decimal
- /*0x0E*/ short scaleFloatBankEntryCount;
+|-
- /*0x10*/ short rotationShortBankEntryCount;
+| <center>0x0A</center> || short || Duration || The number of frames in the animation
- /*0x12*/ short translateFloatBankEntryCount;
+|-
- /*0x14*/ int jointAnimationEntriesOffset;
+| <center>0x0C</center> || short || Keyframe Count || The total number of keyframes, times 3
- /*0x18*/ int scaleFloatBankOffset;
+|-
- /*0x1C*/ int rotationShortBankOffset;
+| <center>0x0E</center> || short || Scale Table Count || The number of entries in the scale table
- /*0x20*/ int translateFloatBankOffset;
+|-
- //From 0x24 to 0x40 is the standard padding string: "This is padding data to alig".
+| <center>0x10</center> || short || Rotation Table Count || The number of entries in the rotation table
+|-
-After this header is the animation data.
+| <center>0x12</center> || short || Translation Table Count || The number of entries in the rotation table
 == LoopMode ==
@@ Line 72: / Line 82: @@
 | <center>0x30</center> || TrackData || Translation Z || Translation of the Z coordinate
 |}
 Each TrackData is 0x06 bytes long, with the following layout:
@@ Line 85: / Line 97: @@
 | <center>0x04</center> || TangentMode || Tangent Mode || The mode of storing animation curve tangents
 |}
 TangentMode is an enum as follows:
@@ Line 110: / Line 124: @@
 The Scale and Translation tables are stored as consecutive floats, and the Rotation table is stored as consecutive signed shorts. Rotation is stored in signed units that range from -0x7FFF to 0x7FFF, corresponding to -180 degrees and 180 degrees, respectively.
-== Calculating the value for an animation track ==
+=== Calculating the value for an animation track ===
-To calculate a single value for a single animation track, [https://en.wikipedia.org/wiki/Hermite_interpolation Hermite interpolation] should be used.
+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 [https://en.wikipedia.org/wiki/Cubic_Hermite_spline Cubic Hermite spline].

@@ Line 1: / Line 1: @@
 '''BCK''' is the format that stores bone animation data for BMD and BDL models. It consists of the standard animation header, followed by BCK-specific data in the ANK1 chunk, with data stored in banks at the end separated by component type - scale, rotation, and translation.
-=Standard Header=
+=JSYSTEM Header=
-This header is found at the start of all the animation formats. Below is what it looks like for the BCK format.
+The file starts with a standard [[JSYSTEM#Header|JSYSTEM]] header, using a magic of J3D1bck1. BCK files have one chunk, the ANK1 chunk.
 ==Header==
@@ Line 37: / Line 26: @@
 After this header is the animation data.
 == Animation Data ==

@@ Line 95: / Line 95: @@
 Using the Index, Count, and Tangent Mode values for the curves, the decoding is as follows:
-. If the Count field is 1, then there is no curve, and instead, a single value is stored in the table at Index.
+# If the Count field is 1, then there is no curve, and instead, a single value is stored in the table at Index.
-. 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).
+# 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).
-. 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.
+# 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.
-. If this is a Rotation table, then left-shift the Values and Tangents by the Rotation Frac field in the header. Time is unaffected.
+# If this is a Rotation table, then left-shift the Values and Tangents by the Rotation Frac field in the header. Time is unaffected.
 The Scale and Translation tables are stored as consecutive floats, and the Rotation table is stored as consecutive signed shorts. Rotation is stored in signed units that range from -0x7FFF to 0x7FFF, corresponding to -180 degrees and 180 degrees, respectively.

@@ Line 36: / Line 36: @@
   //From 0x24 to 0x40 is the standard padding string: "This is padding data to alig".
-After this header is the keyframe data.
+After this header is the animation data.
-==Keyframe Data==
+== Animation Data ==
-There are 9 keyframes for each bone - 1 each for the X, Y, and Z components of scaling, rotation, and translation. The layout of these keyframes is shown below.
+There are 9 animation tracks stored in each animation table.
- //0x36/54 bytes long
+{| class="wikitable"
- // X components
+|-
- /*0x00*/ Keyframe ScaleX;
+! Offset                !! Type !! Name !! Description
- /*0x06*/ Keyframe RotationX;
+|-
- /*0x0C*/ Keyframe TranslationX;
+| <center>0x00</center> || TrackData || Scale X || Scale of the X coordinate
- // Y components
+|-
- /*0x12*/ Keyframe ScaleY;
+| <center>0x06</center> || TrackData || Scale Y || Scale of the Y coordinate
- /*0x18*/ Keyframe RotationY;
+|-
- /*0x1E*/ Keyframe TranslationY;
+| <center>0x0C</center> || TrackData || Scale Z || Scale of the Z coordinate
- // Z components
+|-
- /*0x24*/ Keyframe ScaleZ;
+| <center>0x12</center> || TrackData || Rotation X || Rotation of the X coordinate
- /*0x2A*/ Keyframe RotationZ;
+|-
- /*0x30*/ Keyframe TranslationZ;
+| <center>0x18</center> || TrackData || Rotation Y || Rotation of the Y coordinate
-The keyframes are grouped according to their components, and are always in the order of scale/rotation/translation.
+Each TrackData is 0x06 bytes long, with the following layout:
-Each keyframe is 6 bytes long, with the following layout:
+{| class="wikitable"
- //0x6/6 bytes long
+TangentMode is an enum as follows:
-Thus, a keyframe contains the number of keys that will be interpolated over the course of the animation, the index of the first key in the relevant data bank, and a short with an unknown purpose.
+{| class="wikitable"
-This section is padded to the nearest 32 bytes with the standard padding string.
+== Animation Curve Data ==
-=Data Banks=
+The tables for the individual component types store the component data. That is, the Scale Table stores the values for the Scale X, Scale Y, and Scale Z tracks, the Rotation Table stores the values for the Rotation X, Rotation Y, and Rotation Z tracks, and the Translation Table stores the values for the Translation X, Translation Y and Translation Z tracks.
-There are 3 data banks after the keyframe data that store the keys for scaling, rotation, and translation. The scale and translation values are stored as floats, but the rotation values are stored as shorts.
+Using the Index, Count, and Tangent Mode values for the curves, the decoding is as follows:
-Each bank begins with one "default" value that the keyframes can reference when they don't need to sample any keys. For scale, this is 1.0f; for rotation, this is 0; and for translation, this is 0.0f. This default is just the value, but every key after it follows this format:
+. If the Count field is 1, then there is no curve, and instead, a single value is stored in the table at Index.
- var Timestamp;
+The Scale and Translation tables are stored as consecutive floats, and the Rotation table is stored as consecutive signed shorts. Rotation is stored in signed units that range from -0x7FFF to 0x7FFF, corresponding to -180 degrees and 180 degrees, respectively.
-The timestamp and the tangent are stored in the same datatype as the value - float for the scale and translation banks, and short for the rotation bank.
+== Calculating the value for an animation track ==