ITM file format

PST

This file format describes an "item". Items include weapons, armor, books, scrolls, rings and more. Items can have attached abilties, occuring either when a target creature it hit, or when the item is equipped. ITM files have a similar structure to SPL files.

ITM files consist of a main header, zero or more extended headers (each containing zero or more feature blocks) and zero or more casting feature blocks. All the feature blocks are stored as a continuous data segment, with each extended header containing an offset into this data, and the main header containing an offset into this data for the casting feature blocks.

Overall structure:

Header
Extended Headers
Equipping Feature Blocks

Offset	Size (datatype)	Description
0x0000	4 (char array)	Signature ('ITM ')
0x0004	4 (char array)	Version ('V1.1')
0x0008	4 (strref)	Unidentified Name (strref)
0x000c	4 (strref)	Identified Name (strref)
0x0010	8 (resref)	Drop sound - played when the item is dropped in the inventory (WAV)
0x0018	4 (dword)	Flags
0x001c	2 (word)	Item type
0x001e	1*4 (byte)	Usability bitmask
0x0022	2 (char array)	Weapon animation (Nameless character only) AX = Axe CL = Club DD = Dagger WH = Warhammer Blank (0x2020) = Fist
0x0024	2 (word)	Min Level
0x0026	2 (word)	Unused
0x0028	2 (word)	Unused
0x002a	2 (word)	Unused
0x002c	2 (word)	Unused
0x002e	2 (word)	Unused
0x0030	2 (word)	Unused
0x0032	2 (word)	Unused
0x0034	4 (dword)	Price
0x0038	2 (word)	Stack amount
0x003a	8 (resref)	Inventory icon (BAM)
0x0042	2 (word)	Lore to ID
0x0044	8 (resref)	Ground icon (BAM)
0x004c	4 (dword)	Weight
0x0050	4 (strref)	Unidentified Description (strref)
0x0054	4 (strref)	Identified Description (strref)
0x0058	8 (resref)	Pickup sound - played when the item is picked up in the inventory (WAV)
0x0060	4 (dword)	Enchantment
0x0064	4 (dword)	Offset to extended headers
0x0068	2 (word)	Count of extended headers
0x006a	4 (dword)	Offset to feature blocks
0x006e	2 (word)	Index into equipping feature blocks
0x0070	2 (word)	Count of equipping feature blocks
0x0072	8 (resref)	Dialog (DLG)
0x007a	4 (strref)	Conversable label (strref)
0x007e	2 (word)	Paperdoll animation colour
0x0080	2 (word)	Unknown
0x0082	4 (dword)	Unknown
0x0086	4 (dword)	Unknown
0x008a	4 (dword)	Unknown
0x008e	4 (dword)	Unknown
0x0092	4 (dword)	Unknown
0x0096	4 (dword)	Unknown

Items can have several "abilities" that correspond to an action the item can do (e.g. melee attacks, projectile attacks, spell-casting etc.). Each of these abilities is specified through an extended header. Only the first three extended headers can have charges (extended headers further than this use the charges of the first extended header). Tooltips for item abilities are set through tooltips.2da.

NB. For items to be stackable, they must contain at least one extension header, even if it is empty.
NB. For an attack type of projectile, if the projectile type is set to 1,2 or 3, the weapon will use the attack speed of the ammunition.

Offset	Size (datatype)	Description
0x0000	1 (char)	Attack type 0 = None 1 = Melee 2 = Projectile 3 = Magic 4 = Launcher
0x0001	1 (char)	ID Req. bit 0: ID Required bit 1: Non-ID Required bit 2: 'Friendly' ability
0x0002	1 (char)	Location 0 = None 1 = Weapon 2 = Spell 3 = Equipment 4 = Innate
0x0003	1 (char)	Alternative dice sides
0x0004	8 (resref)	Use icon
0x000c	1 (char)	Target type 0 = Invalid (cannot be selected) 1 = Creature 2 = Crash 3 = Character potrait 4 = Area 5 = Self 6 = Crash 7 = None (Self, ignores game pause)
0x000d	1 (char)	Target count
0x000e	2 (word)	Range
0x0010	1 (byte)	Projectile type 0 = None 1 = Arrow 2 = Bolt 3 = Bullet
0x0011	1 (byte)	Alternative dice thrown
0x0012	1 (byte)	Speed
0x0013	1 (byte)	Alternative damage bonus
0x0014	2 (word)	THAC0 bonus
0x0016	1 (byte)	Dice sides
0x0017	1 (byte)	Primary type
0x0018	1 (byte)	Dice thrown
0x0019	1 (byte)	Secondary type
0x001a	2 (word)	Damage bonus
0x001c	2 (word)	Damage type 0 = None 1 = Piercing/Magic 2 = Blunt 3 = Slashing 4 = Ranged 5 = Fists
0x001e	2 (word)	Count of feature blocks
0x0020	2 (word)	Index into feature blocks
0x0022	2 (word)	Charges
0x0024	2 (word)	Charge depletion behaviour 0 = Don't vanish 1 = Expended 2 = Expended (w/o sound) 3 = Recharge each day
0x0026	4 (dword)	Flags
0x002a	2 (word)	Projectile animation (projectl.ids/missile.ids)
0x002c	2*3 (word)	Melee animation
0x0032	2 (word)	Unused
0x0034	2 (word)	Unused
0x0036	2 (word)	Unused

Any action carried out by an item is done by feature blocks, each of which holds an effect number as well as targetting and timing information. The engine appears to roll a probability for each valid target type, rather than one probability per attack.

Offset	Size (datatype)	Description
0x0000	2 (word)	Opcode number
0x0002	1 (char)	Target type 0 = None 1 = Self (pre-projectile) 2 = Pre-target 3 = Party 4 = Everyone (inc. party) 5 = Everyone (excl. party)
0x0003	1 (char)	Power
0x0004	4 (dword)	Parameter 1
0x0008	4 (dword)	Parameter 2
0x000c	1 (char)	Timing mode 0 = Duration 1 = Permanent 2 = While equipped 3 = Delayed Duration 4 = Delayed 5 = Delayed (transforms to 8) 6 = Duration? 7 = Permanent? 8 = Permanent (unsaved) 9 = Permanent (after Death) 10 = Trigger 4096 = Absolute duration
0x000d	1 (char)	Resistance The default behaviour is that effects cannot be dispelled and ignore resistance. bit 0: Can be dispelled, affected by resistance bit 1: Ignores resistance (when used in combination with bit 0) This can also be presented in the more traditional way: 0 = Nonmagical 1 = Can be dispelled/Affected by resistance 2 = Cannot be dispelled/Ignores resistance 3 = Can be dispelled/Ignores resistance
0x000e	4 (dword)	Duration
0x0012	1 (char)	Probability 1
0x0013	1 (char)	Probability 2 Note: The BG1 engine treats probability as a single word, effects are applied in the range 0-probability. Note: Other engines treat probability as two values, effects are applied in the range probability <= x <= probability. Probability range is 0-99
0x0014	8 (resref)	Resource
0x001c	4 (dword)	Dice Thrown
0x0020	4 (dword)	Dice Sides
0x0024	4 (dword)	Saving throw type bit 0: Spells bit 1: Breathe bit 2: Death bit 3: Wands bit 4: Polymorph NB. If more than 1 saving throw type is specified, the target rolls against their best save.
0x0028	4 (dword)	Saving throw bonus
0x002c	4 (dword)	Special

Bit	Byte 1	Byte 2	Byte 3	Byte 4
0	Unsellable (critical item)	Silver	Unused	Unused
1	Two-handed	Cold-Iron	Unused	Unused
2	Movable	Steel	Unused	Unused
3	Displayable	Conversable	Unused	Unused
4	Cursed	Pulsating	Unused	Unused
5	Cannot scribe to spellbook (scrolls)	Unused	Unused	Unused
6	Magical	Unused	Unused	Unused
7	Unused	Unused	Unused	Unused

The item type of an item affects the pick-up/put-down sound when moving the item in the inventory, whether stores will buy the item and the ability buttons shown on the item description screen.

Code	Item type
0x0000	Books/misc
0x0001	Amulets and necklaces
0x0002	Armor
0x0003	Belts and girdles
0x0004	Boots
0x0005	Arrows
0x0006	Bracers and gauntlets
0x0007	Helms, hats, and other head-wear
0x0008	Keys (not in Icewind Dale?)
0x0009	Potions
0x000a	Rings
0x000b	Scrolls
0x000c	Shields (not in IWD)
0x000d	Food
0x000e	Bullets (for a sling)
0x000f	Bows
0x0010	Daggers
0x0011	Maces (in BG, this includes clubs)
0x0012	Slings
0x0013	Small swords
0x0014	Large swords (in BG, this includes 2-handed and bastard swords)
0x0015	Hammers
0x0016	Morning stars
0x0017	Flails
0x0018	Darts
0x0019	Axes (specifically, 1-handed axes -- halberds and 2-handed polearms not included)
0x001a	Quarterstaff
0x001b	Crossbow
0x001c	Hand-to-hand weapons (fist, fist irons, punch daggers, etc)
0x001d	Spears
0x001e	Halberds (2-handed polearms)
0x001f	Crossbow bolts
0x0020	Cloaks and robes
0x0021	Gold pieces (not an inventory item, but can appear as "monster dropped" treasure)
0x0022	Gems
0x0023	Wands
0x0024	Containers/eye/broken armor
0x0025	Broken shields/bracelets
0x0026	Broken swords/earrings
0x0027	Tattoos (PST)
0x0028	Lenses (PST)
0x0029	Bucklers/teeth
0x002a	Candles
0x002b	Unknown
0x002c	Clubs (IWD)
0x002d	Unknown
0x002e	Unknown
0x002f	Large Shields (IWD)
0x0030	Unknown
0x0031	Medium Shields (IWD)
0x0032	Notes
0x0033	Unknown
0x0034	Unknown
0x0035	Small Shields (IWD)
0x0036	Unknown
0x0037	Telescopes (IWD)
0x0038	Drinks (IWD)
0x0039	Great Swords (IWD)
0x003a	Container
0x003b	Fur/pelt
0x003c	Leather Armor
0x003d	Studded Leather Armor
0x003e	Chain Mail
0x003f	Splint Mail
0x0040	Half Plate
0x0041	Full Plate
0x0042	Hide Armor
0x0043	Robe
0x0044	Unknown
0x0045	Bastard Sword
0x0046	Scarf
0x0047	Food (IWD2)
0x0048	Hat
0x0049	Gauntlet

Bit	Byte 1	Byte 2	Byte 3	Byte 4
0	Unusable by Chaotic	Unusable by Godsmen	Unusable by Indeps	Unusable by Ignus
1	Unusable by Evil	Unusable by Anarchist	Unusable by Fighter Thief	Unusable by Morte
2	Unusable by Good	Unusable by Chaosmen	Unusable by Mage	Unusable by Nordom
3	Unusable by Good-Evil Neutral	Unusable by Fighter	Unusable by Mage Thief	Unknown
4	Unusable by Lawful	No Faction	Unusable by Dak'kon	Unusable by Annah
5	Unusable by Lawful-Chaotic Neutral	Unusable by Fighter Mage	Unusable by Fall-From-Grace	Unknown
6	Unusable by Sensates	Unusable by Dustmen	Unusable by Thief	Unusable by Nameless One
7	Unusable by Priest	Unusable by Mercykillers	Unusable by Vhailor	Unknown

Bit	Byte 1	Byte 2
0	Add strength bonus	Unknown
1	Breakable	Unknown
2	Unknown	Hostile
3	Unknown	Recharges
4	Unknown	Unknown
5	Unknown	Unknown
6	Unknown	Unknown
7	Unknown	Unknown