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 tileset index, palette and 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()).