WORLD.DAT
The original XCOM file is 13320 bytes long, while TFTD is 14660 bytes long. However, each uses the same 20-byte record format giving the original 666 entries and TFTD 733 entries. This file describes the terrain on the geoscape screen using quadrilateral polygons and triangles.
The first 16 bytes of file contain the points for the polygon. 4 sets of 2 short (2-byte) integers, designating the 'X' and 'Y' coordinate (or latitude and longitude if you prefer). If the last set has an x value of -1 then it is to be rendered as a triangle, otherwise it is a quad.
The last 4 bytes in the record contain the terrain type. This could be a long integer or 2 short integers as the last 2 bytes in each record are 0.
Structure
| Offsets | Meaning | Values |
|---|---|---|
| 0-1 | First X coordinate | 0 - 2880 |
| 2-3 | First Y coordinate | -720 - 720 |
| 4-5 | Second X coordinate | 0 - 2880 |
| 6-7 | Second Y coordinate | -720 - 720 |
| 8-9 | Third X coordinate | 0 - 2880 |
| 10-11 | Third Y coordinate | -720 - 720 |
| 12-13 | Fourth* X coordinate | 0 - 2880 |
| 14-15 | Fourth* Y coordinate | -720 - 720 |
| 16-19 | Terrain Type/Texture | 0-12 |
* As mentioned above, the fourth coordinate could be (-1, 0) denoting a triangle
As the possible latitude values range from 0 to 2880 and the longitude values range from -720 to 720, the resulting map could be said to have a resolution of 00°07'30" (one-eighth of a degree) both in latitude and in longitude.
The X coordinate increases going eastward. As might be expected from forcing a positively oriented coordinate system for algorithmic purposes, A Y coordinate value of 720 corresponds to 90°S; a Y coordinate value of -720 corresponds to 90°N.
Texture / Terrain Type
The final value in each record points to the texture type to be displayed for that polygon. It also serves to determine the terrain type used when you start a battle in that area.
UFO TFTD 0: Forest / Jungle 0: (Nothing?) 1: Farm 1: Pipes 2: Farm 2: Crashed Plane 3: Farm 3: Atlantis 4: Farm 4: Mu 5: Mountain 5: Sunken Galleon 6: Forest / Jungle 6: Sunken Liner 7: Desert 7: Volcanic 8: Desert 8: (Nothing?) 9: Polar Ice 9: Volcanic 10: Forest / Jungle 10: Sunken Liner 11: Forest / Jungle 11: Pipes 12: Polar Seas w/Icebergs 12: Mu
In UFO, terrain types 0, 6, 10 and 11 will produce forest missions in the northern hemisphere and jungle mission in the south. (11 is not actually used in the game, but hacking reveals this.)
For TFTD, the terrain type is always selected randomly from a choice of three - Coral, Seabed, and whatever the terrain type for that actual polygon is. In the case of a type 0 or 8, the mission will always be in either the Coral or Seabed terrains.
Although TFTD has three choices of underwater depth that can be associated with any given mission (plus a forth "depth" for surface missions), that value is not derived from this file. Most likely it's taken from the LOC.DAT record that points to the mission in concern.
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Rendering of the data in WORLD.DAT for the original XCOM. The colors are obtained by using offset 16-19 for each record. Click on the image to see the exact color key, generally speaking though it goes bright green to dark green for 0-5, and dark yellow to white for 6 - 12. Value 11 however is not used anywhere in the map. |
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Rendering of the data in WORLD.DAT for TFTD. Colors again are obtained by using the same offset as before. They go from blue to white for 0 to 12. |
TFTD seems to have overlapping polygons at places whereas XCOM didn't (exception to the poles, which is probably because these polygons are rendered to a sphere, not a flat surface).
--Pi Masta 15:24, 10 April 2007 (PDT)
Each polygon has its light calculated individually. This gives rise to the effect of a large area of the same texture having different colors, depending on how much sunlight the particular area defined by the WORLD.DAT record is receiving.
Country and regional borders must be stored in the executable somewhere. I've tried hard looking for the position of cities in there hoping the position would be near its ENGLISH.DAT index, but I haven't had much luck.
--Pi Masta 16:06, 10 April 2007 (PDT)