ArmA 1 Generic File Format Data Types

ArmA 1 aka Armed Assault (ArmA)

Generic File Format Data Types

Intro

This is a generic list of data types encountered in all file formats. Not all of which will be used in a specific file format.

They are listed here, rather than repetitive typing in each of file format's documentation.

Little endian byte order, lsb first for numeric values, text is stored in Big endian byte order.

Type	Description
byte	unsigned 8 bit (1 byte)
char	signed 8 bit Ascii(utf8) character
char[]	fixed length string
tbool	byte (0 = false).
short	16 bit signed short (2 bytes)
ushort	16 bit unsigned short (2 bytes)
long	32 bit signed integer (4 bytes)
ulong	32 bit unsigned integer (4 bytes)
float	32 bit IEEE-single precision floating point value (4 bytes)
double	64 bit IEEE-double precision floating point value (8 bytes)
asciiz	Null terminated (0x00) variable length ascii string
asciiz…	zero or more concatenated asciiz strings
ascii	fixed length ascii string(UTF-8)

XYPair
{
	ulong x,y; // normally associated with cell sizes
}

XYZTriplet
{
	float    x,y,z;
}

Normally, this structure is associated with positional information.

RGBAColor
{
	byte r,g,b,a; // // 0xFF:FF:FF:FF means 'default'
}

RGBA colors correspond to Microsoft's D3DCOLORVALUE
They normally come in pairs inside the pew structures to reflect object and outline colors

LenString
{
	ulong  Length;
	Asciiz Characters[[Length]];// null terminated regardless.
};

Length always =strlen(Characters)+1;

This is a pre-calculated convenience to reduce load times (and skip over the variable length block).

This is the transform matrix as used by Microsoft DirectX. Known as row-vector format

In fact, the 'correct' matrix is actually 4 x 4, but the last column always represents 0,0,0,1 thus

M11, M12, M13 (0.0)
M21, M22, M23 (0.0)
M31, M32, M33 (0.0)
M41, M42, M43 (1.0)

And so is never stored. This identical matrix is used for WRP files (both formats) and RTM files.

In this documentation the above matrix is represented as XYZTriplets

struct TransformMatrix
{
	XYZTriplet XYZ[[4]];
};

The last row:

M41..., or XYZ[[3]]...

corresponds to the position of the object.

Pew files hold this data in Column, rather than row, vectors, as per OpenGL. Thus;

Wrp

ABC
DEF
GHI
JKL

Pew

ADGJ
BEHK
CFIL

And is repesent structurally as

struct PewTransform
{
	float[[3]][[4]];
};

Note that 'int' is not used in this documentation for the following reasons:

an 'int' is machine and compiler and language dependent. It is an arbitrary size SIGNED value.
with exceptions, bis use floats when requiring negative values.
almost all references to 'integers' in bis file formats are either positive-only offsets into memory, zero based indexes, and counts.
the incidence of true shorts and true integers in bis is quite rare. Exception -1 is a favourite, to indicate default