SCUMM/Technical Reference/Room resources

SCUMM V1

A room resource is located as the first chunk in a LFL File.

Header

The room resource starts with a 28 bytes header containing the following information:

Location	Format	Data
0x00	UInt16LE	Size of the room resource chunk
0x02	???	Unknown
0x04	UInt16LE	Room width in tiles
0x06	UInt16LE	Room height in tiles
0x08	???	Unknown (Always 0 on NES)
0x0a	UInt16LE	Offset to gfx nametable location (NES)
0x0c	UInt16LE	Offset to gfx attrtable location (NES)
0x0e	UInt16LE	Offset to mask flag value location
0x10	???	Unknown (On NES both these values are equal)
0x12	???	Unknown
0x14	UInt8	Number of objects in room
0x15	UInt8	Offset to number of boxes location
0x16	UInt8	Number of sounds in room (Always 0 on NES)
0x17	UInt8	Number of scripts in room
0x18	UInt16LE	Offset to exit script location
0x1a	UInt16LE	Offset to entry script location

All offsets are relative to the start of the chunk.

Note: Because of the following constraints:

• Offset to box number location is stored as an UInt8, thus must be within the first 255 bytes of the chunk
• The header takes 28 bytes
• The combined size of object image and object code offsets is 4 bytes per object

The total number of objects per room must be less than 57:

(256 - 28) / 4 = 57

Content

Object image offsets

From byte 0x1c starts the offsets to object images:

Location	Format	Data
0x1c	UInt16LE	Offset to object 1 image location
0x1e	UInt16LE	Offset to object 2 image location
...	UInt16LE	Repeated objNum times

Object code offsets

From there, there is the list of offsets to each object code:

Location	Format	Data
0x1c + objNum * 2	UInt16LE	Offset to object 1 content location
0x1e + objNum * 2	UInt16LE	Offset to object 2 content location
...	UInt16LE	Repeated objNum times

Number of boxes

The boxes number in the room is located at the boxes number offset specified in the header.

Location	Format	Data
Offset to number of boxes	UInt8	Number of boxes in room

Note: Some LFL files have unknown data between the last object code offset and the boxes number offset location. For most file however, both data are contiguous.

Boxes

2 bytes after the offset to number of boxes starts the payload for the boxes. Each box takes 8 bytes described as follow:

Relative location	Format	Data
0x00	UInt8	uy
0x01	UInt8	ly
0x02	UInt8	ulx
0x03	UInt8	urx
0x04	UInt8	llx
0x05	UInt8	lrx
0x06	UInt8	mask
0x07	UInt8	flags

Box matrix

Immediately following the last box payload is the box matrix.

There are boxNum * boxNum number of them read as UInt8.

Object code

The object code section has the following structure starting from its corresponding object code offset:

Object code header

Relative location	Format	Data
0x00	UInt8	Size of the object code chunk
0x02	???	Unknown (Always 0 on NES)
0x03	???	Unknown (Always 0 on NES)
0x04	UInt16LE	The object number (used to reference object in scripts)
0x06	??	Unknown (Always 0 on NES)
0x07	UInt8	X position of object
0x08	UInt8	Y position of object + Object parent state
0x09	UInt8	Object width in tiles
0x0a	UInt8	Object parent
0x0b	UInt8	Walk to X position
0x0c	UInt8	Walk to Y position
0x0d	UInt8	Actor facing direction + Object height in tiles
0x0e	UInt8	Offset to object name

Note: The object code data starts at byte 15, the verb-script pairs part ends with a 0x00 byte. This means that the object name offset value is always an even number between 16 and 254.

Object code content

Object code content contains 3 optional sections, in this order:

• 0 or more pairs of verb ids and object script offsets
• The name of the object
• 0 or more object scripts

Object script offsets

From byte 15, 2 UInt8 are read 2 by 2.

The first one is a reference to the verb ID and the second is an offset to the beginning of the object script.

Multiple verbs can refer to the same offset.

This part ends with a 0x00.

Object name

The object name starts at specified offset. Each character is read until a 0x00 value is found.

Object script

Each object script ends with 0x00 (Opcode for stopObjectCode()).