David Simpson posted:

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// CELL.DAT
//
// Cell.dat, along with portal.dat, contains the majority of the data used in
// Asheron's Call. Cell.dat is the storage area for Turbine's own file system.
// The file is essentially a collection of sectors (or cells). Each sector is
// 256 bytes in length. The first 1KB of the file is different though. Each
// "file" is made up of multiple sectors, though the sectors are not necessarily
// contiguous. The "files" are indexed from a directory. The first word of
// each sector is a pointer to the next sector of that "file." A NULL pointer
// indicates that this is the last sector in that file.

// The Map
//
// The map in Asheron's Call is 254 by 254 landblocks. Each landblock contains
// a 9 by 9 grid of data points which makes for an 8 by 8 group of land squares
// in game. Each landblock has a unique id, which is a word in length, and
// has the format xxyyFFFF. In game, xx is the east-west position, and yy is the
// north-south position. Landblock 0000FFFF is located in the southwest corner of
// the map. Use /loc to find out which landblock you are on. Each square in a
// landblock is 0.1 wide and tall, making each landblock 0.8 by 0.8. Although
// each landblock contains 9 by 9 points, the points on the edges are redundant
// with adjacent landblocks. The entire map is 2041 by 2041 data points, making
// 2040 by 2040 squares. Lastly, each square is 24.0 by 24.0 units, whatever
// they may be.

// Landblock Data
//
// The topography data for each landblock is stored in just one sector. It's
// data format is as follows:
//
// uint Next sector pointer (will be 0)
// uint Landblock id (xxyyFFFF)
// uint Object Block Present
// ushort Topo[9][9]
// uchar Z[9][9]
// uchar Pad (always 0, I think)
//
// Object Block Present is a flag which signifies that there is an object block
// associated with this landblock. The id of the object block is xxyyFFFE.
// The Z data is exactly what it sounds like: height information. In game,
// the height of a point is 2.0 * Z.
// The Topo contains the land type, road information, and what I believe is
// vegetation type and/or density. It is as follows:
//
// bits
// 0 Road
// 1 Unknown (draws a road though)
// 2-6 Land Type
// 7 Unknown (may be more land type, always 0 though)
// 8-15 Vegetation
//
// Roads always have an underlying land type. Bit 1 is very rare in the data,
// but in tests, just draws a road like bit 0. Currently, most of the land
// types are used, except those of 0x60, 0x70, 0x74, 0x78, and 0x7C which are
// not currently found in game. Recently, 0x6C was added and 0x68 was changed.
// I don't know much about the vegetation bits other than that is what they
// seem to be.

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