Difference between revisions of "SCUMM/Technical Reference/Room resources"

<tr><td>0x0a</td><td>UInt16LE</td><td>Offset to 1 byte for the tileset index, followed by 16 bytes of palette data, and then the RLE encoded nametable data (NES)</td></tr>

<tr><td>0x0e</td><td>UInt16LE</td><td>Offset to the mask flag location, which if 1 is followed by the RLE encoded mask data</td></tr>

* Offset to box number location is stored as an UInt8, thus must be within the first 255 bytes of the chunk

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

There are a minimum of <code>boxNum * boxNum</code> entries read as UInt8. Each entry has at least 2 pairs of 3 byte sets which determine connecting boxes. The table allows more values to be used in each entry if necessary. Example pseudo code:

   var boxm = boxMatrix[from];

   if (boxm[0] <= to && to <= boxm[1])

     return boxm[2];

   if (boxm[3] <= to && to <= boxm[4])

     return boxm[5];

The two bytes at <code>0x0a</code> of the room data point to the tileset index which is used to look up the tileset in a separate table. The tileset table provides the bank and memory offset for the given tileset.

The two bytes at <code>0x0c</code> of the room data point to the RLE encoded attribute table (NES). The amount of data is decoded according to the rom height and width.

If the mask flag is <code>0x01</code> then the RLE encoded mask data follows. This is bitmap data where each bit corresponds to a single tile, so a single byte covers a row of 8 tiles. A bit value of 1 = masked (background priority), and 0 = unmasked (sprite priority). The bits in each byte are reversed (or read right to left) before they are applied.

Next starts the data that is pointed to by the object image offsets beginning at byte 0x1c in the room data. This is RLE encoded nametable and attribute table data for each. The amount of data for each object is based on the height and width of the object. The data is RLE encoded per row. These graphical updates are triggered in SCUMM by `setState08` and `clearState08`.

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

<tr><td>0x04</td><td>UInt16LE</td><td>The object number (used to reference object in scripts). The object number must be 255 (0xFF) or less to be able to be picked up.</td></tr>

<tr><td>0x08</td><td>UInt8</td><td>Object parent state + Y position of object (<code>0xSSSYYYYY</code>). Parent state is always <code>0x04</code> if present and is used in combination with the Object parent value at <code>0x0a</code> to hide objects behind doors (think the refrigerator).</td></tr>

<tr><td>0x0c</td><td>UInt8</td><td>Preposition + Walk to Y position (<code>0xPPPYYYYY</code>). Possible preposition values are: <code>0x001</code> = in, <code>0x010</code> = with, <code>0x011</code> = on.</td></tr>

<tr><td>0x0d</td><td>UInt8</td><td>Object height in tiles + Actor facing direction (<code>0xHHHHHDDD</code>). Possible facing values are: <code>0x100</code> = left, <code>0x101</code> = right, <code>0x110</code> = front (facing player), <code>0x111</code> = back (facing away from player).</td></tr>

'''Note:''' The object code data starts at byte 15. The verb-script pairs terminate with a null byte (0x00). This means that the object name offset value is always an even number 16 or above.

Starting at byte 15, two UInt8 values are read at a time.