ANM format (.anm)

Overview

Format .anm is used to store animations of skeletal models in engines of the GEM family. GEM RTS supports all previous versions of the animation format. Each file may contain:

• frame range parameters;

• bone map;

• animation keys;

• visibility data;

• mesh animation;

• optional comments.

File structure

EANM
version
FRMS
    frame_max + 1
CMNT
    size
    comment[size]
BMAP
    bone_count
    bones [bone_count]
        bone_name
frame cycle
    FRMN | FRM2 | FRM3

Chunks

File Header

Content verifier. Confirms that the file contains animation.

Name	Type	Size	Description
FourCC	uint8[4]	4	EANM
version	int16[2]	4	Format version. The first 2 bytes contain major, the second 2 bytes contain minor: 0x00040000 version 4.0 (GEM1, Soldiers Heroes of World War II) 0x00060000 version 6.0 (GEM2, Men of War) 0x00060001 version 6.1 (GEM2.5, Majesty2; GEM RTS, Men of War II) GEM RTS supports all versions

Chunk FRMS

Specifies the maximum frame number in the animation.

Data structure

FRMS
    frame_max + 1

Name	Type	Size	Description
FourCC	uint8[4]	4	FRMS
frame_max + 1	int32	4	The value is 1 greater than the maximum frame number.

Chunk CMNT

An optional comment chunk. Also used as a GEM3 format flag.

Data structure

CMNT
    size
    comment[size]

Name	Type	Size	Description
FourCC	uint8[4]	4	CMNT
size	uint16	2	Comment size in bytes
comment	char[size]	1+	Comment text

Chunk BMAP

Animation bones map. Supports LOD via suffix ._lod<lod_number> in the name of a bone.

Data structure

BMAP
    bone_count
    bones[bone_count]
         bone_name

Name	Type	Size	Description
FourCC	uint8[4]	4	BMAP
bone_count	int32	4	The number of bones in the map. Regardless of type int32, version 6.1 supports no more than 255 bones
bones	struct[bone_count]		Bone data array

Description of the bone array

Name	Type	Size	Description
bone_name	string8/24 or string32	1+	Name of the bone. If the GEM3 format is used, the following applies string8/24. For older formats, use string32

Frame cycles

After the bone map, a sequence of animation frames begins.

Data structure

frame cycle
    FRMN | FRM2 | FRM3

The chunk type depends on the animation format version.

Frame format identifier	Version	Comment
FRMN	V1	Supported since GEM1
FRM2	V2	Supported since GEM2
FRM3	V3	Supported since GEM2.5 / GEM RTS

*) GEM RTS supports all format versions.

Frame format V1 (FRMN)

Used in GEM1.

Data structure

FRMN
frame_no
cycle
     BONE
     index
     cycle
          MATR
               matrix
          VISI
               visibility
          MESH
               size
               mesh_data[size]

Frame Verifier V1

Name	Type	Size	Description
FourCC	uint8[4]	4	FRMN
frame_no	int32	4	Frame number

Chunk BONE

Contains animation of a single bone.

Name	Type	Size	Description
FourCC	uint8[4]	4	BONE
index	int32	4	Bone index from the BMAP table

Chunk MATR

Bone transformation matrix.

Name	Type	Size	Description
FourCC	uint8[4]	4	MATR
matrix	float[3][4]	48	3x4 matrix. Contains: position, orientation, scale

Chunk VISI

Visibility of a bone.

Name	Type	Size	Description
FourCC	uint8[4]	4	VISI
visibility	int32	4	Visibility flag. Values: 0 - invisible 1 - visible

Chunk MESH

Mesh animation.

Name	Type	Size	Description
FourCC	uint8[4]	4	MESH
size	int32	4	Mesh animation data size
mesh_data	uint8[size]		Mesh animation data

Frame Format V2 (FRM2)

Used in GEM2.

Data structure

FRM2
frame_no
key_count

keys[key_count]
bone_map_index
key_flags

[if key_flags & 0x0001]
            position

[if key_flags & 0x0002]
            orientation

[if key_flags & 0x0040]
            scale

[if key_flags & 0x0020]
            mesh
                size
                data[size]

Frame Verifier V2

Name	Type	Size	Description
FourCC	uint8[4]	4	FRM2
frame_no	uint16	2	Frame number
key_count	uint8	1	Number of animated keys per frame
keys	struct[key_count]		Key description structure

Key structure (struct[key_count])

Name	Type	Size	Description
bone_map_index	uint8	1	Bone index from the BMAP table
key_flags	uint16	2	Bitmask of animated parameters

Bit mask for key_flags

Bit	Description
0x0001	Position
0x0002	Orientation
0x0004	Sign of a mirrored matrix
0x0008	Turning on visibility
0x0010	Turning off visibility
0x0020	Mesh animation
0x0040	Scale

Key data

Fields are present only if the corresponding bit is set in key_flags.

Name	Type	Size	Description
position	float[3]	12	Position
orientation	float[3]	12	Normalized form of a quaternion
scale	float[3]	12	XYZ scale
mesh	struct		Mesh animation
mesh.size	int32	4	Data size
mesh.data	uint8[size]		Binary data of mesh animation

Frame format V3 (FRM3)

Used in GEM2.5 and GEM RTS.

Data structure

FRM3
    frame_no

    keys[key_count]
        bone_map_index
        key_flags

[if key_flags & 0x0001]
            position

[if key_flags & 0x0002]
            orientation

[if key_flags & 0x0040]
            scale

[if key_flags & 0x0020]
            mesh
                size
                mesh_data[size]

Frame Verifier V3

Name	Type	Size	Description
FourCC	uint8[4]	4	FRM3
frame_no	uint8 uint16 uint32	1 2 4	The field size depends on frame_max. Used by: uint8, if frame_max <= 255 uint16, if frame_max <= 65535 uint32, if frame_max >= 65536
key_count	uint8	1	Number of animated keys per frame
keys	struct[key_count]		Key description structure

Key structure (struct[key_count])

Name	Type	Size	Description
bone_map_index	uint8	1	Bone index from the map BMAP table
key_flags	uint16	2	Bitmask of animated parameters

Bit mask (key_flags)

Meaning	Description
0x0001	Position
0x0002	Orientation
0x0004	Sign of a mirrored matrix
0x0008	Turning on visibility
0x0010	Turning off visibility
0x0020	Mesh animation
0x0040	Scale

Key data

Fields are present only if the corresponding bit is set in key_flags.

Name	Type	Size	Description
position	float[3]	12	Position
orientation	float[3]	12	Normalized form of a quaternion
scale	float[3]	12	XYZ scale
mesh	struct		Mesh animation
mesh.size	int32	4	Data size
mesh.data	uint8[size]		Binary data of mesh animation