ANIM (File Format)

This file format is almost completely documented Having trouble with bone rotations +/- 180 degrees in format 2

The ANIM format is used in conjunction with the CINF and CSKR to animate rigged CMDL meshes.

There are two versions of the ANIM format in Metroid Prime (indicated by the file's first long value):

Version	Description
0x0	Quaternion Array Format
0x2	Rotation Vector Bitstream Format

Quaternion Array Format

The Quaternion Array Format (0x0) is a less common animation format in Metroid Prime. It's only used in a Ridley intro animation and the rotating pirate data artifact hologram above the Impact Crater.

The format maps animation channels to bones and supplies rotations as an array of quaternion (WXYZ) keys. Optionally, translations may be specified for a subset of bones as an array of float3 keys.

Data Type	Element Count	Identifier	Notes
Header0	1	header
char	header‑>bone_entry_count	bone_entry_map	The index-positions of this table correspond to the bone ids in the associated CINF. The value is 0xff if the bone is not animated by this ANIM or an index relating the bone_translation_map and quaternion_key_array below
long	1	bone_channel_count	Count of bone channels present in the bone_translation_map and quaternion_key_array below
char	bone_channel_count	bone_translation_map	Each bone channel may be optionally augmented with translation vectors at the bottom of the file. The index-positions of this table correspond to the values in the bone_entry_map above. The value is 0xff if the bone is not translated by this ANIM or an index relating the quaternion_key_array below
long	1	quaternion_key_count	Count of elements in quaternion_key_array below
float4	quaternion_key_count	quaternion_key_array	The quaternion keys are interleaved like such (bone-major): |------------|------------|-----|------------| | bone0/key0 | bone0/key1 | ... | bone0/keyN | | bone1/key0 | bone1/key1 | ... | bone1/keyN | | .......... | .......... | ... | .......... | | boneN/key0 | boneN/key1 | ... | boneN/keyN | |------------|------------|-----|------------|
long	1	translation_key_count	Count of elements in translation_key_array below
float3	translation_key_count	translation_key_array	The translation keys are interleaved like such (bone-major): |------------|------------|-----|------------| | bone0/key0 | bone0/key1 | ... | bone0/keyN | | bone1/key0 | bone1/key1 | ... | bone1/keyN | | .......... | .......... | ... | .......... | | boneN/key0 | boneN/key1 | ... | boneN/keyN | |------------|------------|-----|------------| Any bone channels that were marked 0xff in the bone_translation_map are skipped by this array
long	1	evnt_ref	ID for this ANIM's EVNT resource, or 0xffffffff if no events triggered

Header0

Offset	Length	Data Type	Identifier	Notes
0x0	4	float	duration	Time in seconds that the animation plays for
0x4	4	float	key_interval	Time in seconds between keys of each bone channel (reciprocal of frame-rate)
0x8	4	long	bone_entry_count	Count of bone-channels in animation
0xC	4	long	key_count	Count of keys for each bone channel (keys are set for every frame of the animation)

Rotation Vector Bitstream Format

The Rotation Vector Bitstream Format is the most widely used animation format in Metroid Prime. The format uses a compressed bitstream to store keys that have been delta encoded and quantized to make for a very compact, compressed animation. The data is processed sequentially to reconstruct the decompressed bone channel data.

In addition to the bitstream quantization, the format includes a bitmap specifying which frames of the animation have keys added. Consequently, the runtime constructs missing keys via interpolation (reducing animation size further).

Header2

Offset	Length	Data Type	Identifier	Notes
0x0	4	long	scratch_size	Amount of memory that the animation system needs to allocate to process animation
0x4	4	long	evnt_ref	ID for this ANIM's EVNT resource, or 0xffffffff if no events triggered
0x8	4	long	unknown0	Always 0x1
0xC	4	float	duration	Time in seconds that the animation plays for
0x10	4	float	interval	Time in seconds between keys of each bone channel (reciprocal of frame-rate)
0x14	4	long	unknown1	Always 0x3
0x18	4	long	unknown2	Always 0x0
0x1C	4	long	rotation_divisor	Rotation vectors are divided by this value before being applied
0x20	4	float	translation_multiplier	Translation vectors are multiplied by this value before being applied
0x24	4	long	bone_channel_count	Count of bone channels present in ANIM
0x28	4	long	unknown3	Always 0x1
0x2C	4	long	key_bitmap_length	Number of bits in key bitmap